Vehicle Body Engineering by M A Qadeer Siddiqui

VEHICLE CODY ENGINEERING AND SAFETY

M A QADEER SIDDIQUI

BY

MOHD ABDUL QADEER SIDDIQUI 1


M A QADEER SIDDIQUI

Roadmap to syllabus VEHICLE BODY ENGINEERING AND SAFETY UNIT 1: Structural materials Aluminum alloy sheet, extrusion and casting,austentite and ferrite stainless steels, different types of composites,FPR and Metal Matrix Composite, structural timbers-properties designing in GRP and high strength composites different manufacturing techniques of composites, Thermo plastics, ABS and styrene, load bearing plastics, semi-rigid PUR foams and sandwich panel construction UNIt2: Shaping and packaging: Product design and concepts, Aesthetics and industrial design, formal aesthetics and shape. Computer aided drafting, surface development, interior ergonomics, ergonomics system design, dash –board instruments, advances in electronic display, CV legal dimension, CV-cab ergonomics, and Mechanical package layout. Unit 3: Aerodynamics Basics,aerofoils,aerodynamics drag lift,pitching,yawing and rolling moments, determination of aerodynamics coefficient(wind tunnel testing), racing car aerodynamics, bluff body aerodynamics, local air flows. Unit4: Load distribution: Types of load carrying structures-closed,integral,open,flat types, calculation of loading cases-static,asymmetric,vertical loads, load distribution, stress analysis of structure, body shell analysis. Unit5: Body Fitting and I control: Driver‘s seat, window winding mechanism ,door lock mechanism, other interior mechanism, driver‘s visibility and test for visibility, minimum space, requirements and methods or improving space in cars, electric wiring and electronic control systems, advanced body electronics, networking or body system controls Unit 6: Noise, vibration, harshness: Noise and vibration basics, body structural vibrations, chassis bearing vibration, designing against fatique,rubber as an isolator, CV body mounting, automatic enclosure, sandwich panels, structure dynamics applied, surety under impacts, Impact protection basics, design for crash worthiness ,occupant and cargo restrains, passive restraints systems, side impact analysis ,bumper system ,energy absorbent foams, law of mechanism applied to safety.

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UNIT 7: Vans, Trucks, and busses: types of Mini coach with trailers, single and double deckers,design criteria based on passenger capacity ;goods to be transported and distance to be covered, constructional details, weight and dimensions, Convectional and integral type UNIT 8: Vehicle Stability: Steering geometry vehicle and curvilinear path, and lateral stability, effects of tyre factors, mass distribution and engine location on stability.

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1) Structural Material

Aluminum Alloy Sheets for Automobile Panel

Features   

The TM Series (type 6000 alloy) is bake hardened, making its lightweight and strong. The TG Series (type 5000 alloy) is highly ductile, lightweight and with high formability. We offer a variety of products with different surface finishes, surface treatments, lubricants and sizes. Specification Description Material Type 5000 or 6000 rolled sheet alloy Surface finishes Dull or milled finished Surface Acid washing possible treatments Lubricants Can be coated with various types of lubricant Coils and sheets (longitudinal circular sheets also Shapes possible)

Applications Automotive panel materials (engine hoods, trunk lids, doors, etc.)

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Product Characteristics Typical characteristics of aluminum alloy sheets used to make automobile panels Alloy proof strength Tensile Yield By alloy Elongation By after strength strength Alloy and quality (Note1) quality baking TS(MPa) YS(MPa) EL (%) YS(MPa) 5052

O

195

90

27

5182

O

270

130

28

5000 TG19 Alloys

O

270

125

30

TG25

O

275

120

33

TM30

T4

210

110

27

TM45

T4

245

135

29

6000 Alloys TM55

T4

230

120

29

TM66

T4

240

115

29

High BHTM67

T4

255

120

29

High T4 formability-

285

145

29

Notes

General materials General materials Good formability, SS-mark improvement High formability, SS-mark improvement High BH, superior 200 corrosion resistance Good formability, 165 superior corrosion resistance High BH, superior 220 corrosion resistance Good 210 formability, High BH Good 215 formability, High BH High 175 formability 5


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TM67 Steel SPCC 314 176 42 Reference sheet Note 1 Baking conditions: After applying 2% pre-distortion, test value after 20 min at 170°C Note 2 The "stretcher-strain mark" (SS mark) is a distortion pattern that appears during forming. Note 3 The BH (bake-hard effect) is the property of strength increased by applying the bake coating.

Extrusion Extrusion is the process by which long straight metal parts can be produced. The cross-sections that can be produced vary from solid round, rectangular, to L shapes, T shapes. Tubes and many other different types. Extrusion is done by squeezing metal in a closed cavity through a tool, known as a die using either a mechanical or hydraulic press. Extrusion produces compressive and shear forces in the stock. No tensile is produced, which makes high deformation possible without tearing the metal. The cavity in which the raw material is contained is lined with a wear resistant material. This can withstand the high radial loads that are created when the material is pushed the die. Extrusions, often minimize the need for secondary machining, but are not of the same dimensional accuracy or surface finish as machined parts. Surface finish for steel is 3 µm; (125 µ in), and Aluminum and Magnesium is 0.8 µm (30 µ in). However, this process can produce a wide variety of cross-sections that are hard to produce cost-effectively using other methods. Minimum thickness of steel is about 3 mm (0.120 in), whereas Aluminum and Magnesium is about 1mm (0.040 in). Minimum cross sections are 250 mm2 (0.4 in2) for steel and less than that for Aluminum and Magnesium. Minimum corner and fillet radii are 0.4 mm (0.015 in) for Aluminum and Magnesium, and for steel, the minimum corner radius is 0.8mm (0.030 in) and 4 mm (0.120 in) fillet radius.

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Cold Extrusion: Cold extrusion is the process done at room temperature or slightly elevated temperatures. This process can be used for most materialssubject to designing robust enough tooling that can withstand the stresses created by extrusion. Examples of the metals that can be extruded are lead, tin, aluminum alloys, copper, titanium, molybdenum, vanadium, steel. Examples of parts that are cold extruded are collapsible tubes, aluminum cans, cylinders, gear blanks. The advantages of cold extrusion are: • No oxidation takes place. • Good mechanical properties due to severe cold working as long as the temperatures created are below the re-crystallization temperature. • Good surface finish with the use of proper lubricants. Hot Extrusion: Hot extrusion is done at fairly high temperatures, approximately 50 to 75 % of the melting point of the metal. The pressures can range from 35-700 MPa (5076 - 101,525 psi). Due to the high temperatures and pressures and its detrimental effect on the die life as well as other components, good lubrication is necessary. Oil and graphite work at lower temperatures, whereas at higher temperatures glass powder is used. Typical parts produced by extrusions are trim parts used in automotive and construction applications, window frame members, railings, aircraft structural parts.

Casting In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool 7


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and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods. Casting processes have been known for thousands of years, and widely used for sculpture, especially in bronze, jewellery in precious metals, and weapons and tools. Traditional techniques include lost-wax casting, plaster mold casting and sand casting. The modern casting process is subdivided into two main categories: expendable and non-expendable casting. It is further broken down by the mold material, such as sand or metal, and pouring method, such as gravity, vacuum, or low pressure

Austenitic stainless steel Austenitic stainless steels have high ductility, low yield stress and relatively high ultimate tensile strength, when compare to typical carbon steel. Carbon steel on cooling transforms from Austenite to a mixture of ferrite and cementite. With austenitic stainless steel, the high chrome and nickel content suppress this transformation keeping the material fully austenite on cooling (The Nickel maintains the austenite phase on cooling and the Chrome slows the transformation down so that a fully austenitic structure can be achieved with only 8% Nickel). Heat treatment and the thermal cycle caused by welding, have little influence on mechanical properties. However strength and hardness can be increased by cold working, which will also reduce ductility. A full solution anneal (heating to around 1045°C followed by quenching or rapid cooling) will restore the material to its original condition, removing alloy segregation, sensitization, sigma phase and restoring ductility after cold working. Unfortunately the rapid cooling will re-introduce residual stresses, which could be as high as the yield point. Distortion can also occur if the object is not properly supported during the annealing process. Austenitic steels are not susceptible to hydrogen cracking, therefore preheating is seldom required, except to reduce the risk of shrinkage stresses in thick sections. Post weld heat treatment is seldom required as this material as a high resistance to brittle fracture; occasionally stress relief is carried out to reduce the risk of stress corrosion cracking, however this is likely to cause sensitization unless a stabilized grade is used (limited stress relief can be achieved with a low temperature of around 450°C ) 8


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Ferrite Stainless steel Plain chromium steels (12 to 27 percent chromium) with no significant nickel content which results in lower corrosion resistant than austenitic stainless steels. However, they have slightly higher yield strengths and much lower strain hardening than austenitic. Ferritic steels have body centered cubic crystal, are less ductile than austenitic steel, and are not hardenable by heat treatment like martensitic steels. Older ferritics (such as AISI 409 and 430) are used mainly for household utensils and other applications not demanding in anticorrosion properties. Ferritics with high chromium content (such as AISI 446) are used mainly for high temperature (but below 475°C) applications and those with extremely low carbon and nitrogen content (such as S44400) are used where protection against stress corrosion cracking is required. They are the second largest selling type of stainless steels behind austenitic.

ALLOY STEELS Steel is a metal alloy consisting mostly of iron, in addition to small amounts of carbon, depending on the grade and quality of the steel. Alloy steel is any type of steel to which one or more elements besides carbon have been intentionally added, to produce a desired physical property or characteristic. Common elements that are added to make alloy steel are molybdenum, manganese, nickel, silicon, boron, chromium, and vanadium. Alloy steel is often subdivided into two groups: high alloy steels and low alloy steels. The difference between the two is defined somewhat arbitrarily. However, most agree that any steel that is alloyed with more than eight percent of its weight being other elements beside iron and carbon, is high alloy steel. Low alloy steels are slightly more common. The physical properties of these steels are modified by the other elements, to give them greater hardness, durability, corrosion resistance, or toughness as compared to carbon steel. To achieve such properties, these alloys often require heat treatment. If the carbon level in a low alloy steel is in the medium to high range, it can be difficult to weld. If the carbon content is lowered to a range of 0.1% to 0.3%, and some of the alloying elements are reduced, the steel can achieve a greater weldability and formability while maintaining the strength that steel is known for. Such metals are classified as high strength, low alloy steels. Perhaps the most well-known alloy steel is stainless steel. This is a steel alloy with a minimum of 10% chromium content. Stainless steel is more resistant to stains, corrosion, and rust than ordinary steel. It was discovered 9


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in 1913 by Harry Brearley of Sheffield, England, but the discovery was not announced to the world until 1915. Stainless steel is commonly used in table cutlery, jewelry, watch bands, surgical instruments, as well as in the aviation industry. Its familiar luster has also been appropriated for many famous architectural designs, such as the Gateway Arch in St. Louis, Missouri, and the pinnacle of the Chrysler Building in New York City. In all types of alloy steel, the alloying elements tend to either form carbides or compounds, rather than simply being uniformly mixed in with the iron and carbon. Nickel, aluminum, and silicon are examples of the elements that form compounds in the steel. Tungsten and vanadium will form carbides, both of which increase the hardness and stability of the finished product.

Alloy steel - steel whose characteristics are determined by the addition of other elements in addition to carbon Steel - an alloy of iron with small amounts of carbon; widely used in construction; mechanical properties can be varied over a wide range Chromium steel, stainless, stainless steel - steel containing chromium that makes it resistant to corrosion Chrome-nickel steel, Elinvar - Elinvar is a trademark for a kind of steel used for watch springs because its elasticity is constant over a wide range of temperatures Chrome-tungsten steel - a steel alloy made with chromium and tungsten Austenitic manganese steel, manganese steel - a steel with a relatively large component (10-14%) of manganese; highly resistant to wear and shock Molybdenum steel - steel containing 10-15% molybdenum; properties are similar to tungsten steel Nickel steel - an alloy steel containing nickel Tool steel - alloy steel that is suitable for making tools; is hard and tough and can retain a cutting edge Tungsten steel, wolfram steel – a very hard heat-resistant steel containing tungsten Vanadium steel - steel alloyed with vanadium for greater strength and hightemperature stability

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DIFFERENT TYPES OF COMPOSITES What are composite materials? Composites are a unique class of materials made from two or more distinct materials that when combined are better (stronger, tougher, and/or more durable) than each would be separately. They are non-corroding, nonmagnetic, radar transparent and they are designed to provide strength and stiffness where it is needed. Although many man-made materials have two or more constituents, such as metallic alloys, but they are usually not classified as composites because the structural unit is formed at microscopic level (it means that the combination of materials are combined in such a way that the individual components are indistinguishable) rather than at the macroscopic level (that means the constituents retain their identities in the composite, they do not dissolve or otherwise merge completely into each other). In composite materials, the components can be physically identified and exhibit an interface between one another. The most common composite is the fibrous composite consisting of reinforcing fibers embedded in a binder, or matrix materials.

IMPORTANCE Composites have properties, which could not be achieved by either of the constituent materials alone. We can see that composites are becoming more and more important as it can help to improve our quality of life. Composites are put into service in flight vehicles, automobiles, boats, pipelines, buildings, roads, bridges, and dozens of other products. Researchers are finding ways to improve other qualities of composites so they may be strong, lightweight, long-lived, and inexpensive to produce.

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Different type of composites Actually the production of composites is an attempt to copy nature. Wood is a composite of cellulose fibers cemented together with lignin. This kind of composite is called natural composites. And for man-made composites, there are polymer matrix composites (PMCs), metal matrix composites (MMCs) and ceramic matrix composites (CMCs). They are made from adding reinforcing fibres into polymer matrix, metal matrix or ceramic matrix respectively. Polymer Matrix Composites (PMC‘s) - These are the most common and will be the main area of discussion in this website. Also known as FRP - Fiber Reinforced Polymers - these materials use a polymer-based resin as the matrix, and a variety of fibers such as glass and carbon as the reinforcement. For example ―fiberglass‖, the first successful modern composites, is one of the polymer matrix composites. It is used for making boat hulls, storage tanks, pipes, and car components. Metal Matrix Composites (MMC‘s) - Increasingly found in the mobile industry, these materials use a metal such as aluminum as the matrix, and reinforce it with fibers such as silicon carbide. Ceramic Matrix Composites (CMC‘s) - Used in very high temperature environments, these materials use a ceramic as the matrix and reinforce it with short fibers, such as those made from silicon carbide and boron nitride. Disadvantages of composite materials Although composite materials have certain advantages over conventional materials, composites also have some disadvantages. The common one is the high manufacturing costs. However, as improved manufacturing techniques are developed, it will become possible to produce composite materials at higher volumes and at a lower cost than is now possible. FRP (Fiber Rain forced Composites) Faber-reinforced plastic (FRP) (also fiber-reinforced polymer) is a composite material made of a polymer matrix reinforced with fibers. The fibers are usually glass, carbon, basalt or aramid, although other fibers such as paper or wood or asbestos have been sometimes used. The polymer is usually an epoxy, vinyl ester or polyester thermosetting plastic, and phenol 12


M A QADEER SIDDIQUI

formaldehyde resins are still in use. FRPs are commonly used in the aerospace, automotive, marine, and construction industries. A polymer is generally manufactured by Step-growth polymerization or addition polymerization. When combined with various agents to enhance or in any way alter the material properties of polymers the result is referred to as a plastic. Composite plastics refer to those types of plastics that result from bonding two or more homogeneous materials with different material properties to derive a final product with certain desired material and mechanical properties. Faber-reinforced plastics are a category of composite plastics that specifically use fiber materials to mechanically enhance the strength and elasticity of plastics. The original plastic material without fiber reinforcement is known as the matrix. The matrix is a tough but relatively weak plastic that is reinforced by stronger stiffer reinforcing filaments or fibers. The extent that strength and elasticity are enhanced in a fiberreinforced plastic depends on the mechanical properties of both the fiber and matrix, their volume relative to one another, and the fiber length and orientation within the matrix. Reinforcement of the matrix occurs by definition when the FRP material exhibits increased strength or elasticity relative to the strength and elasticity of the matrix alone. What is FRP? Fiberglass-reinforced plastic is one of the strongest and most durable materials in the world. Bedford manufactures most of its profiles out of fiberglass-reinforced polymers (FRP), also known as ―composites,‖ which are a combination of:    

Resin, such as polyester or vinyl ester; Reinforcements, such as fiberglass roving and mat; Additives, such as pigments, UV inhibitors, fire retardant, etc.; and Surface veil, which enhances corrosion resistance, UV protection and appearance

These materials work in concert to provide a specific set of strength and performance properties, including:      

Light weight with high strength Corrosion free and impact resistant Dimensional stability Electrically non-conductive Non-magnetic and non-sparking Low thermal conductivity 13

VEHICLE CODY ENGINEERING AND SAFETY  

M A QADEER SIDDIQUI

Rapid installation with standard tools RF transparency

MMC (Metal Matrix composites) A metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite. An MMC is complementary to a cermets. Composition MMCs are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. For example, carbon fibers are commonly used in aluminum matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminum to generate a brittle and water-soluble compound Al4C3 on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel or titanium boride. Matrix The matrix is the monolithic material into which the reinforcement is embedded, and is completely continuous. This means that there is a path through the matrix to any point in the material, unlike two materials sandwiched together. In structural applications, the matrix is usually a lighter metal such as aluminum, magnesium, or titanium, and provides a compliant support for the reinforcement. In high temperature applications, cobalt and cobalt-nickel alloy matrices are common. Reinforcement The reinforcement material is embedded into the matrix. The reinforcement does not always serve a purely structural task (reinforcing the compound), but is also used to change physical properties such as wear resistance, friction coefficient, or thermal conductivity. The reinforcement can be either continuous, or discontinuous. Discontinuous MMCs can be isotropic, and can be worked with standard metalworking techniques, such as extrusion, forging or rolling. In addition, they may be machined using conventional techniques, but commonly would need the use of polycrystalline diamond tooling (PCD).

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Continuous reinforcement uses monofilament wires or fibers such as carbon fiber or silicon carbide. Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength. One of the first MMCs used boron filament as reinforcement. Discontinuous reinforcement uses "whiskers", short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide. Application  





Carbide drills are often made from a tough cobalt matrix with hard tungsten carbide particles inside. Some tank armors may be made from metal matrix composites, probably steel reinforced with boron nitride, which is a good reinforcement for steel because it is very stiff and it does not dissolve in molten steel. Some automotive disc brakes use MMCs. Early Lotus Elise models used aluminum MMC rotors, but they have less than optimal heat properties and Lotus has since switched back to cast-iron. Modern highperformance sport cars, such as those built by Porsche, use rotors made of carbon fiber within a silicon carbide matrix because of its high specific heat and thermal conductivity. 3M sells a preformed aluminum matrix insert for strengthening cast aluminum disc brake calipers, allowing them to weigh as much as 50% less while increasing stiffness. 3M has also used alumina performs for AMC pushrods. Ford offers a Metal Matrix Composite (MMC) driveshaft upgrade. The MMC driveshaft is made of an aluminum matrix reinforced with boron carbide, allowing the critical speed of the driveshaft to be raised by reducing inertia. The MMC driveshaft has become a common modification for racers, allowing the top speed to be increased far beyond the safe operating speeds of a standard aluminum driveshaft.

TIMBERS in AutomobilesThe Weymann system comprises an ultra-light wood framework with special metal joints so that timber does not touch timber. Small metal panels are inserted between the fabric and the framework to make rounded external corners. Straining wires are fitted to hold the doors in shape when they are stressed by acceleration or bumps. The frame is then covered with muslin over chicken wire with a thin layer of cotton batting used to span large open areas and over this a top layer of fabric, usually a pigmented synthetic leather, is placed. Any exposed joints in the fabric are covered with aluminum moldings. The seats are fixed directly to the chassis.

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Passengers were therefore in almost direct contact with the firmly mounted engine. Where the market permitted some isolation was provided by luxuriously sprung passenger-seating often topped with inflated pneumatic cushions. For the luxury market it further encouraged the development of inherently smoother multi-cylinder engines in place of sixes and eights and, too late for Weymann, the introduction of flexible engine mounts and better chassis suspension systems in place of primitive leaf springs.

Fiber glass is an excellent example of a relatively modern composite material (Invented in 1938 by Russell Games). In industry it is often referred to as Glass Reinforced Plastic (GRP). GRP is composed of strands of glass. Each individual glass fiber is very fine with a small diameter, and they are woven to form a flexible fabric. The fabric is normally placed in a mould, for instance a mould for a canoe and polyester resin is added, followed by a catalyst (to speed up the reaction). The process is repeated so that there are many layers of fiber glass and resin and allowed to dry/cure. The resulting material is strong and light. Glass Reinforced Plastic can be sanded for a smooth finish and painted. Three samples of different weaves of fiberglass are seen below. The pattern of weave determines the strength and weight of the Glass Reinforced Plastic, after resin has been added. Different weaves have been developed for different practical applications.

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Glass reinforced plastic is lightweight and has good thermal insulation properties. It has a high strength to weight ratio, making it useful for the production of products such as water tanks, surfboards, canoes, small boat hulls and similar products. The new European fighter plane, called ‗Eurofighter‘, has an airframe which includes 12% glass reinforced plastic. TWO TYPICAL USES OF GRP

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GRP (Glass reinforced fiber)

Properties of GRP Glass-reinforced plastic (GRP), also known as glass fiber-reinforced plastic (GFRP) is a lightweight, extremely strong, and robust material. These advantages of using GRP over other materials include: Freedom of Design The practical uses of GRP are virtually endless and it has literally bought the designers imagination to life. GRP opened many new avenues for creative designers. Its unique physical properties allow it to be easily tooled, molded and manufactured to meet almost any specifications. With GRP there are few constraints on size, shape, color or finish, the styling and appearance can take precedence over manufacturing costs. Versatility and Affordability The lightweight strength of GRP makes it a popular choice for manufacturing. GRP reduces weight and requires less maintenance making it highly attractive over more traditional materials like timber, metal or brick. 18


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The flexibility of GRP and the cost effectiveness of its composite materials also make it an extremely affordable solution and an economical alternative. By using GRP industry can manufacture virtually any component or finished product in any quantity. Strength and Durability GRP has a high strength to weight ratio and high flexural strength making it an attractive lightweight material that builds strength into almost any finished product or component. Pound for pound GRP can be stronger than steel and sheet metals. GRP also has high resistance to environmental extremes and requires very little maintenance - no rust, no painting, no wood rot plus GRP is noncorrosive and has a much longer life expectancy when compared to a variety of construction materials. In highly corrosive environments GRP is the preferred choice over metal, wood, or plastic. GRP provides resistance to ultra violet light, extreme temperatures, salt air, and a variety of chemicals including most acids. As GRP is chemically inert and corrosion-resistant, it offers an economical alternative to stainless steel. Appearance GRP products can be manufactured in numerous finishes, textures and colors including brick and stone effect. With sheet metal, you get a plain box. GRP products have sleek contours and a superior molded appearance. Dielectric GRP is non-conductive, RF transparent, and helps to insulate against electromagnetic fields, making GRP the obvious choice for electrical and electronic equipment storage like electrical meter boxes and cabinets. Acoustic Properties GRP provides superior acoustical properties when compared to plastic or metal. Various type of sound deadening materials can be laminated between high strength layers of GRP to achieve the preferred level of sound deadening. GRP parts have excellent dimensional stability and will hold their shapes under severe mechanical and environmental stresses.

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Properties of GRP Glass-reinforced plastic (GRP), also known as glass fiber-reinforced plastic (GFRP) is a lightweight, extremely strong, and robust material. These advantages of using GRP over other materials include: 

Freedom of Design

The practical uses of GRP are virtually endless and it has literally bought the designers imagination to life. GRP opened many new avenues for creative designers. Its unique physical properties allow it to be easily tooled, molded and manufactured to meet almost any specifications. With GRP there are few constraints on size, shape, color or finish, the styling and appearance can take precedence over manufacturing costs. 

Versatility and Affordability

The lightweight strength of GRP makes it a popular choice for manufacturing. GRP reduces weight and requires less maintenance making it highly attractive over more traditional materials like timber, metal or brick. The flexibility of GRP and the cost effectiveness of its composite materials also make it an extremely affordable solution and an economical alternative. By using GRP industry can manufacture virtually any component or finished product in any quantity. 

Strength and Durability

GRP has a high strength to weight ratio and high flexural strength making it an attractive lightweight material that builds strength into almost any finished product or component. Pound for pound GRP can be stronger than steel and sheet metals. GRP also has high resistance to environmental extremes and requires very little maintenance - no rust, no painting, no wood rot plus GRP is non-corrosive and has a much longer life expectancy when compared to a variety of construction materials.

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In highly corrosive environments GRP is the preferred choice over metal, wood, or plastic. GRP provides resistance to ultra violet light, extreme temperatures, salt air, and a variety of chemicals including most acids. As GRP is chemically inert and corrosion-resistant, it offers an economical alternative to stainless steel. 

Appearance

GRP products can be manufactured in numerous finishes, textures and colours including brick and stone effect. With sheet metal, you get a plain box. GRP products have sleek contours and a superior molded appearance. 

Dielectric

GRP is non-conductive, RF transparent, and helps to insulate against electromagnetic fields, making GRP the obvious choice for electrical and electronic equipment storage like electrical meter boxes and cabinets. 

Acoustic Properties

GRP provides superior acoustical properties when compared to plastic or metal. Various type of sound deadening materials can be laminated between high strength layers of GRP to achieve the preferred level of sound deadening. GRP parts have excellent dimensional stability and will hold their shapes under severe mechanical and environmental stresses. High strength CompositesWhat Is Carbon Fiber? Before you can understand how carbon fiber can help solve the oil crisis, you have to understand what it is. Carbon fiber is a super strong material that's also extremely lightweight. Engineers and designers love it because it's five times as strong as steel, two times as stiff, yet weighs about two-thirds less. Carbon fiber is basically very thin strands of carbon -- even thinner than human hair. The strands can be twisted together, like yarn. The yarns can be woven together, like cloth. To make carbon fiber take on a permanent shape, it can be laid over a mold, then coated with a stiff resin or plastic (kind of like how you would make something out of papier-mâché by putting

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newspaper strips over a mold, then adding paste to force it to hold the shape). Most car components are made of steel. Replacing steel components with carbon fiber would reduce the weight of most cars by 60 percent. That 60 percent drop in weight would, in turn, reduce that car's fuel consumption by 30 percent and cut greenhouse gas and other emissions by 10 to 20 percent that‘s a huge fuel savings, even without changing the car's engine. With a lighter carbon fiber body, car makers could build cars with smaller, more efficient engines, or increase the use of electric engines, resulting in even more fuel savings. Reducing weight, increasing fuel efficiency and allowing for the development of different kinds of engines: That's how carbon fiber can solve the oil crisis. The Difficulties of Carbon Fiber Only a few cars available at your local dealership use carbon fiber. The BMW M6 has some carbon fiber panels on its body, as does the Chevrolet Corvette ZR1 and the Ford GT. The Audi R8 also includes some carbon fiber. What do all these cars have in common? They cost a lot of money -- most start above $100,000. It's rare to see a car with carbon fiber because it's expensive! Ten years ago, carbon fiber cost $150 a pound. Now, the price is around $10 a pound. Steel, on the other hand, costs less than a dollar per pound. Many analysts say that for carbon fiber to make it into widespread use in cars, the price will have to drop to about $5 per pound Cost is the main hurdle carbon fiber will have to overcome before it can provide a viable energy solution. The second hurdle is waste disposal. When a typical car breaks down, its steel can be melted and used to construct another car (or building, or anything else made of steel). Carbon fiber can't be melted down, and it's not easy to recycle. When it is recycled, the recycled carbon fiber isn't as strong as it was before recycling. Carbon fiber recycled from a car isn't strong enough to be used in building another car. That's a big issue. Having more cars use carbon fiber would save a lot of oil, but it could also generate a lot of waste. As it stands now, carbon fiber could solve the oil crisis. It's lightweight, durable and safe. But it's also expensive and difficult to recycle. For now, it looks like carbon fiber is just going to be one of many solutions to the oil crisis. When combined with efficient engines, other, cheaper materials and a change in driving habits, carbon fiber is just one piece of the energy puzzle.

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Carbon fiber body Thermoplastic A thermoplastic (sometimes written as thermo plastic) is a type of plastic made from polymer resins that becomes a homogenized liquid when heated and hard when cooled. When frozen, however, a thermoplastic becomes glass-like and subject to fracture. These characteristics, which lend the material its name, are reversible. That is, it can be reheated, reshaped, and frozen repeatedly. This quality also makes thermoplastics recyclable. There are dozens of kinds of thermoplastics, with each type varying in crystalline organization and density. Some types that are commonly produced today are polyurethane, polypropylene, polycarbonate, and acrylic. Celluloid, which is considered the first thermoplastic, made its appearance in the mid-1800s and reigned in the industry for approximately 100 years. During its peak production, it was used as a substitute for ivory. Today, it is used to make guitar picks. Sometimes, thermoplastics are confused with thermosetting plastics. Although they may sound the same, they actually possess very different properties. While thermoplastics can be melted to a liquid and cooled to a solid, thermosetting plastics chemically deteriorate when subjected to heat. Ironically, however, thermosetting plastics tend to be more durable when allowed to cool than many thermoplastics.

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Tensile Yield Strength Tensile yield strength is the maximum engineering stress in psi (or Pa) at which a permanent non-elastic deformation of the thermoplastic material begins. Yield Point Yield point is the first point where the specimen yields, where the specimen's cross-sectional area begins to contract significantly, or where the strain can increase without increase in the stress. Ultimate Tensile Strength Ultimate tensile strength is the maximum stress the thermoplastic material can withstand before failing, whichever occurs at the higher stress level. Tensile Modulus Tensile modulus or Young's Modulus is the ratio of stress to strain within the elastic region of the stress-strain curve before the yield point. Thermoplastic Characteristics

ABS - Acrylonitrile Butadiene Styrene Acrylonitrile Butadiene Styrene (ABS) is the polymerization of Acrylonitrile, Butadiene, and Styrene monomers. Chemically, this thermoplastic family of plastics is called "terpolymers", in that they involve the combination of three different monomers to form a single material that draws from the properties of all three. ABS possesses outstanding impact strength and high mechanical strength, which makes it so suitable for tough consumer products. Additionally, ABS has good dimensional stability and electrical insulating properties. Dynalab Corp's plastic fabrication shop fabricates thousands of catalog and custom ABS products. Strong and rigid resistant to a variety of bases and acids some solvents and chlorinated hydrocarbons may damage the material maximum usable temperature 160oF (71oC) common as DEV Drainage, Waste and Vent - pipes PB - Polybutylene 

flexible pipe 24

VEHICLE CODY ENGINEERING AND SAFETY   

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used for pressurized water systems usable for hot and cold water only compression and banded type joints used

PE - Polyethylene   

flexible pipe Used for pressurized water systems - sprinkler. not usable for hot water

PEX - Polyethylene Cross Linked  

flexible pipe Used for pressurized water systems - sprinkler.

PP - Polypropylene    

lightweight temperature up to 180oF (82oC) highly resistant to acids, bases and many solvents usable in laboratory plumbing

PVC - Polyvinyl Chloride      

strong and rigid resistant to a variety of acids and bases may be damaged by some solvents and chlorinated hydrocarbons maximum usable temperature 140oF (60oC) usable for water, gas and drainage systems not useable in hot water systems

CPVC - Chlorinated Polyvinyl Chloride 

similar to PVC - but designed for water up to 180oF (82oC)

PVDF - Polyvinylidene Fluoride    

strong and very tough material resistant to abrasion, acids, bases, solvents and much more usable to 280oF (138oC) usable in laboratory plumbing

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Styrene Styrene, also known as vinyl benzene and phenyl ethene, is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations confer a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers. Approximately 25 million tons (55 billion pounds) of styrene was produced in 2010. Styrene is essential in the creation of many products that we use every day. A few of the most familiar uses of styrene include: 

 

Solid and film polystyrene, used in rigid foodservice containers, CD cases, appliance housings, envelope windows and many other products. Polystyrene foam, used in food service products and building insulation. Composite products, used in tub and shower enclosures, automobile body panels, wind turbine parts, boats and many other applications.

Other styrene-based materials include:   



ABS plastic, used in refrigerator liners, medical devices, small household appliances and luggage. SAN plastic, used for food containers and optical fibers. SB Rubber (SBR), which reduces dependence on natural rubbers and provides improved performance in applications such as vehicle tires, leading to improved fuel efficiency. SB latex (SBL) used in many paper coatings and in more than 90% of the carpeting made in the United States to attach carpet fibers to a backing material.

Strength, Durability, Comfort, Safety Styrene is so widely used today because it enables a multitude of products to deliver many benefits that are highly valued by consumers. These benefits include strength, durability, comfort and safety. For example, styrene-based products cushion bicycle helmets, strengthen military armor, create wind power turbines, reduce coal plant emissions, enhance components that make cars and trains lighter and more fuel-efficient, enable manufacturing high-performance and cost-effective recreational products such as boats and other watercraft, and reduce dependence on costly natural resources such as tropical hardwoods used in boats and marble and granite used in homes and buildings. 26


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Sandwich panel construction A sandwich-structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core. The core material is normally low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. Open- and closed-cell-structured foams like polyvinylchloride, polyurethane, polyethylene or polystyrene foams, balsa wood, syntactic foams, and honeycombs are commonly used core materials. Open- and closed-cell metal foam can also be used as core materials. Laminates of glass or carbon fiber-reinforced thermoplastics or mainly thermoset polymers (unsaturated polyesters, epoxies...) are widely used as skin materials. Sheet metal is also used as skin material in some cases. The core is bonded to the skins with an adhesive or with metal components by brazing together.

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UNIT 2) SHAPING AND PACKAGING Product design is the process of creating a new product to be sold by a business to its customers. A very broad concept, it is essentially the efficient and effective generation and development of ideas through a process that leads to new products. In a systematic approach, product designers conceptualize and evaluate ideas, turning them into tangible inventions and products. The product designer's role is to combine art, science, and technology to create new products that other people can use. Their evolving role has been facilitated by digital tools that now allow designers to communicate, visualize, analyze and actually produce tangible ideas in a way that would have taken greater manpower in the past. Product design is sometimes confused with (and certainly overlaps with) industrial design, and has recently become a broad term inclusive of service, software, and physical product design. Industrial design is concerned with bringing artistic form and usability, usually associated with craft design and ergonomics, together to mass-produce goods.Other aspects of product design include engineering design, particularly when matters of functionality or utility (e.g. problem-solving) are at issue, though such boundaries are not always clear. Concept is a fundamental category of existence. In contemporary philosophy, there are at least three prevailing ways to understand what a concept is:   

Concepts as mental representations, where concepts are entities that exist in the brain. Concepts as abilities, where concepts are abilities peculiar to cognitive agents. Concepts as abstract objects, where objects are the constituents of propositions that mediate between thought, language, and referents

Industrial Design is the use of both applied art and applied science to improve the aesthetics, ergonomics, functionality, and/or usability of a product, and it may also be used to improve the product's marketability and even production. The role of an industrial designer is to create and execute design solutions for problems of form, usability, physical ergonomics, marketing, brand development, and sales.

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Industrial design can overlap significantly with engineering design, and in different countries the boundaries of the two concepts can vary, but in general engineering focuses principally on functionality or utility of products whereas industrial design focuses principally on aesthetic and user-interface aspects of products. In many jurisdictions this distinction is effectively defined by credentials and/or licensure required to engage in the practice of engineering."Industrial design" as such does not overlap much with the engineering sub-discipline of industrial engineering, except for the latter's sub-specialty of ergonomics. Aesthetics (also spelled æsthetics) is a branch of philosophy dealing with the nature of art, beauty, and taste, with the creation and appreciation of beauty. It is more scientifically defined as the study of sensory or sensoryemotional values, sometimes called judgments of sentiment and taste. More broadly, scholars in the field define aesthetics as "critical reflection on art, culture and nature." More specific aesthetic theory, often with practical implications, relating to a particular branch of the arts is divided into areas of aesthetics such as art theory, literary theory, film theory and music theory. An example from art theory is aesthetic theory as a set of principles underlying the work of a particular artist or artistic movement: such as the Cubist aesthetic. What is aesthetics? The term 'aesthetics' concerns our senses and our responses to an object. If something is aesthetically pleasing to you, it is 'pleasurable' and you like it. If it is aesthetically displeasing to you, it is 'displeasurable' and you don't like it. Aesthetics involves all of your senses - vision, hearing, touch, taste, and smell - and your emotions. Elements of Aesthetics There are many different things that contribute to your overall perception of a product, and to your opinion as to whether it is aesthetically pleasing to you.

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Vision Colour Shape Pattern Line Texture Visual weight Balance Scale Movement

Hearing Loudness Pitch Beat Repetition Melody Pattern Noise

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Touch Texture Shape Weight Give Comfort Temperature Vibration Sharpness Ease of use

Taste Strength Sweetness Sourness Texture

Smell Strength Sweetness 'Pleasantness'

Your opinion about a product may also be influenced by certain associations that are important to you, such as:     

how fashionable it is whether it is a novelty, or an old favourite whether it is a symbol of wealth or love how much danger or risk is involved if it provides a link with your past

You might also take into account whether it is safe and reliable and fit for its purpose. Consistency with a particular aesthetic concept may be a significant factor in creating a product's appeal too, for example, the current appreciation of 'retro' designs. However, such trends are often cultural and almost certainly always short-lived, so their popularity can't be guaranteed.

Computer Aided Drafting Computer-aided design/drafting (CAD) is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations. 30


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Computer-aided design is used in many fields. Its use in electronic design is known as Electronic Design Automation, or EDA. In mechanical design is known as Mechanical Design Automation, or MDA, it is also known as computer-aided drafting (CAD) which describes the process of creating a technical drawing with the use of computer software. CAD software for mechanical design uses either vector based graphics to depict the objects of traditional drafting, or may also produce raster graphics showing the overall appearance of designed objects. However, it involves more than just shapes. As in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as materials, processes, dimensions, and tolerances, according to applicationspecific conventions.

Ergonomics of vehicle Dictionaries generally define ergonomics as a scientific discipline that uses principles of biotechnology and engineering to make products more comfortable for workers and consumers. But ergonomics isn't just about design. It also factors in how we use things. In the context of a car, that means considering anything from the placement of a radio dial to how a person sits in a passenger seat. One ergonomics engineer for Ford described her job as‖ human factors engineering‖. So while engineers may design cars to be ergonomically friendly, it doesn't mean that one design will work for all users, especially if the car is designed for a person of certain proportions. It's also up to us passengers and drivers to make ourselves comfortable. For instance, if you're a driver and position your seat so that your feet barely reach the pedals, you may induce unnecessary strain on your arms -- just as sitting too close can cause leg or back pain. Seat position, posture and time spent in the car all can affect a person's health. According to one study, if you drive four or more hours a day, you're six times more likely to develop back problems .Musculoskeletal disorders also pose a concern for longdistance drivers, particularly those who drive for a living: truck drivers, taxi drivers, even police officers on patrol.

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In this article, we'll take a look at the design of car ergonomics and how to take full advantage of them for health, comfort, efficiency and safety. First, let's see what role ergonomics play for a person in the driver's seat. Vehicle Surfaces The materials used for vehicle load beds (in rigid, curtain-sided and flatbed vehicles) generally present a low-slip risk when dry, but it is likely that they will become wet during normal use. They may then become slippery. Tests have been carried out on a range of materials used on vehicle load areas, looking at the surface or micro roughness and slip resistance in both wet and dry conditions. Composite resin and aggregate surfaces have been found to give good slipresistance in both wet and dry conditions while aluminium chequer plate performs relatively poorly when wet.

DASH BOARD INTRUMENTS At minimum, your dashboard display has a speedometer and a fuel gauge. In addition to those gauges, the display will feature some combination of a tachometer, charging system gauge, oil pressure gauge and engine temperature gauge. Let's have a quick dashboard confessional that covers what each part does. The speedometer, one of the most frequently used tools, tells you how fast you're going. Traditionally, this gauge relied upon a cable that connected the speedometer to a gear inside the transmission, but now, electric sensors are used with most dashboard devices. Instrument panels basically have a feed of constantly updated information from around the car; in fact, about onehalf of a vehicle's total wiring can be found in the dashboard display. If you drive a stick, you're probably well familiar with the tachometer, which measures revolutions per minute (RPM) in the engine. Knowing this information can help you shift at a time when you'll get maximum fuel economy. Ever needed a jump when your battery went dead? You might have paid more attention to the charging system gauge or warning light afterwards. The amount of electrical current that the charging system provides to your 32


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vehicle's battery is monitored by either a voltmeter, which measures the voltage in the charging system, or an ammeter, which measures amperage leaving the battery. When the battery is using too much of its own juice and depleting itself without getting refilled by the charging system, then these gauges or warning lights should alert you to the problem. While many of us strive to lower our blood pressure, we should never strive to have low oil pressure. The oil pressure gauge measures oil pressure in pounds per square inch, and you're going to have a big problem if that pressure falls in a car. Unless you want to destroy your vehicle, stop the car as soon as possible when this gauge alerts you to a problem; you'll likely be warned via an oil lamp warning light in the dash. Similarly, if your engine gets too hot, you should also get off the road as soon as you can. Your temperature gauge, which measures the temperature of engine coolant, will alert you to a dangerous situation. There are a host of other warning lights designed to let you know about the status of the car. Though there have been some efforts to standardize these lights in all makes and models, they are currently personalized to some extent by car manufacturers. You might see these lights for everything from a reminder that someone's not wearing a seatbelt to a warning that tire pressure is low. For more details about what a certain light is trying to tell you, consult your car's manual. The configuration and arrangement of these instruments varies according to each car. In fact, it may surprise you to learn how much time carmakers spend designing dashboard displays.

Dashboard Display Design First impressions are important, and a dashboard provides your introduction to each automobile you drive. Designers get paid to think about what each person might want from the dashboard, because, unlike with potential partners, you're not likely to ask for a second date with that car if you don't get the information you need upfront. The style, shape and layout of the dashboard can be a deal-breaker when buying a car. That's why some drivers may have a completely electronic dashboard display, while others still watch the rise and fall of a needle; it seems that young drivers and women, in particular, have more of an affinity for the digital model. Some drivers want as much information as possible about their driving and their car; people with displays that show real-time fuel 33


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economy information might make a game out of trying to improve their driving with each mile. The aging baby boomer generation, however, wants basic information in an easy-to-read format. The need to control additional technology, from power mirrors to a stereo system, means that dashboard displays will only become more diverse in the future. In 2006, writers at PC Magazine imagined a future dashboard that included drowsiness sensors, advanced navigation systems and voice recognition systems that allow you to ask your car questions. This dashboard of the future will also let you pick which instrument gauges you want to see at a given time and project that display on the windshield, so that less eye movement is required That means you'll have more time to move your eyes toward the custom entertainment system, full of your favorite music and videos. That begs the question, of course, as to when a dashboard display becomes a dashboard distraction. Safety advocacy groups worry that drivers will perceive that most of the driving is being done for them with dashboard gadgets such as self-parking devices, lane-change alerts and cruise control. These people will pay less attention to the road and their driving, while even those who are trying to pay attention will be distracted by the constant hum of beeps and the constant flash of notifications from the dashboard. There's a balance to strike multitasking and keeping those eyes on the road.

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ADVANCES IN DASH BORAD INSTRUMENTS

LCD instrument panels are coming, trickling down from a handful of expensive cars today to affordable cars. You need an LCD display in front of you to process all the information you‘re getting from the car and connected devices. Any car instrument panel tells you how fast you‘re going and how much fuel remains. When you also want to see navigation instructions, song info, hybrid battery efficiency, and the name of an incoming caller, it‘s time for a big-screen LCD instrument panel. They‘re on a dozen premium car models today. Affordable cars are getting hybrid displays in the instrument panel: The speedometer, tachometer, and fuel gauge are traditional mechanical devices; inset among them or in a bottom strip is an LCD display that can show all the other information. The car instrument panel is following the lead of the center stack in going to LCDs. The instrument cluster or instrument panel is what‘s on the far side of the steering wheel. The center stack is where the radio/head unit and climate control knobs live. Within five years (by 2017), nearly two thirds of cars sold in North America will have a center stack with a display radio, or head unit with an LCD of at least 4.5 inches rather than a dumb, one- or two-line text display, according to IHS Automotive, a Minnesota consulting group. Try scrolling a thousand-song smartphone list on a text display for quick proof of why you want an LCD display. As for the instrument panel, 85% of cars will have at least a partial LCD and more than 10% will be full LCDs. ―Infotainment is the main driver for most display radios,‖ says Mark 35


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Boyadjis, an IHS senior analyst. ―Safety is the main driver for LCD displays in the instrument cluster or small displays in the head unit.‖ The US is requiring all cars built by September 2014 to have a rear camera and display in the cockpit. An LCD backup (reversing) camera display embedded in the inside mirror is acceptable, too, though they‘re small and can be affected by sunlight. The industry hasn‘t yet settled on a term for an instrument panel that uses an LCD or brighter OLED, so you‘ll hear digital dashboard, virtual instrument cluster, reconfigurable instrument cluster, glass cockpit (borrowed from the aviation industry), and digital instrument cluster display (ICD) used to describe the instrument panel of the near future. Information presented in the instrument panel is easier to see at a glance because the driver just looks down, not over and down as with center stack displays. A head-up display is even better, but the cost is around $1,000 and some drivers find them distracting even when they show a pared-down subset of info (speed, cruise-control speed, next turn).

The full monty: 12-inch, all-glass instrument panel Full digital ICDs have been on a handful of cars for 3-4 years. Jaguar and Land Rover were early pioneers in full digital ICDs with the Jaguar XJ and Land Rover‘s Range Rover (pictured above). Both use 12.3-inch LCD panels. At the very least, a full digital instrument panel usually lets the driver switch between a digital and analog speedometer, or even have the digital readout set inside the analog speedometer gauge. Switching from miles to kilometers is a snap when you drive in Canada or Mexico. It could allow the over-40 driver to increase the font size of information. For old farts who maybe shouldn‘t be driving at all, the text could be really big. For the fortysomething driver who needs reading glasses and isn‘t wearing them, or who 36


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has sunglasses ground only for distance vision, larger fonts would make make the make the cockpit information more legible. So far, automakers haven‘t rushed to implement sizable fonts, even though they talk a good game about being sensitive to the boomer population. Cadillac XTS: Move apps from center stack to instrument panel The most recent car to make a splash with a full LCD instrument cluster is the full-size Cadillac XTS (pictured at the top of the story), announced in the spring, and followed by the compact Cadillac ATS sport sedan, with a partial digital ICD. It, too, has a 12.3-inch, 1280×480 panel.

The Cadillac XTS display is highly but not infinitely configurable. First, you can set four themes for the instrument panel display, called Simple, Enhanced, Balanced (photo), and Performance, with less or more information. Then you can tinker with the display elements. The 3-inch center of the speedometer (middle gauge) can be digital speed readout or a moving map. This is part of the Cadillac User Experience (CUE) infotainment package that also includes an 8-inch capacitive touch center stack LCD. The XTS driver can swipe or flick windows of information from the center stack over to the instrument panel LCD. But you can‘t make the map any bigger in the instrument panel or move it to the seemingly underused gauge on the right. Boy racers believe the tachometer (left gauge) redline should point straight up in a properly sporting car run at the track, but that is something you can‘t do, a Cadillac marketing manager said with a bit more NFW emphasis than I thought the question called for. It goes without saying that you can‘t download an instrument panel template and roll your own interface. Yet Hackers, take your marks…

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Partially customizable LCDs Some automakers started their trek to the glass cockpit with partial digital ICDs such as this 2010 BMW 7 Series. The small and large gauges on top are mechanical and that trademark look hasn‘t changed much since the seventies. The strip at the bottom is a wide LCD that you can customize a bit by deciding what elements you‘d like to see. BMW has since expanded to a full digital ICD, 12 inches across, for the 7 Series and 5 Series. The Cadillac ATS, a compact sports sedan, also has a partial digital ICD.

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The eco-friendly partial LCD instrument panel If you build a hybrid, the owner gets, free of charge, all manner of positive reinforcement telling you what great job you‘re doing. Ford calls this attaboy LCD Smart Gauge, a pair of 4.5-inch LCDs flanking the speedometer. If you‘re a conservative driver, you collect green leaves, as on the Ford Fusion Hybrid (pictured above). The driver can customize what the gauges show, including a small navigation screen, phone info, infotainment (artist, track, album), or efficiency on the right. The left-side information can be made more or less complex as well. Ford offers the Smart Gauge on a wide line of cars, not just hybrids that have the My Ford Touch and Ford Sync infotainment system.

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Small MID adds information at low cost A multi-information display (MID) has been in the center of car instrument panels for years and has been upgraded from a text-only display, good for showing the outside temperature or miles to empty, to a small color LCD that can show navigation arrows, MP3 album art, or an icon of the car with information such the four tires‘ pressures. The Chevrolet Malibu Eco (above) is typical of the current genre of smallish LCDs that provide a lot of information for just a few dollars of manufacturing cost.

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The future: LCD instrument panels, two center stack LCDs Can you have too much of a good thing? Concept cars and soon production cars may have high and low LCD displays in the center stack with dual 7- or 8-inch displays. While some higher-end cars have 10-inch displays, IHS‘ Boyadjis says prices are falling most for 8-inch LCDs. A higher panel is better for quickly seeing information. Low is better for touching and swiping with your finger. The Infiniti LE concept car incorporates two center stack panels in addition to to a full digital instrument panel.

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Commercial Vehicle Dimensions Part 2 - Vehicle Weights and Dimensions Limits by Configuration

Category 1: Tractor Semi-trailer Section 1 - Dimension Limits

DIMENSION

LIMIT

Overall Length Overall Width Overall Height Tractor Wheelbase Tandem axle spread

Maximum 23 m1, 2 Maximum 2.6 m3 Maximum 4.15 m4

Semi-trailer Length Wheelbase Kingpin setback Effective rear overhang Tandem axle spread

Maximum 6.2 m5 Minimum 1.2 m/Maximum 1.85 m Maximum 16.2 m Minimum 6.25 m/Maximum 12.5 m6 Maximum 2.0 m radius Maximum 35% of wheelbase7 Minimum 1.2 m/Maximum > 1.85 m 42


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Tridem axle spread Minimum 2.4 m/Maximum 3.7 m Triaxle axle spread Minimum 2.4 m/Maximum 4.8 m Track width Minimum 2.5 m/Maximum 2.6 m Interaxle Spacing Single Axle to Single, Tandem, or Tridem Minimum 3.0 m Axle Tandem Axle to Tandem Axle Minimum 5.0 m Tandem Axle to Tridem Axle Minimum 5.5 m 1 A tractor semi-trailer while being used to transport poles, pipe or material that cannot be dismembered must not exceed a length of 25 m. 2 A tractor semi-trailer designed and being used as an auto carrier must not exceed a length of 23 m when not loaded and 25 m when loaded. 3 The load of a tractor semi-trailer designed and being used as an auto carrier that overhangs the front or rear of the tractor semi-trailer must not have an overall width that exceeds 2.1 m. 4 A tractor semi-trailer designed and being used as an auto carrier must not have an overall height that exceeds 4.15 m when not loaded and 4.30 m when loaded. The driver must ensure there is a safe clearance under any physical overpass, including structures and utility lines. 5 A tractor wheelbase can be up to a maximum of 7.2 m, if the wheelbase of the semi-trailer is not greater than the wheelbase as set out in Schedule A-1. 6 The minimum wheelbase for a semi-trailer, model year 2002 or earlier, is 3.75 m. 7 A tractor semi-trailer designed and being used as an auto carrier must not have a rear overhang that exceeds 35% of the wheelbase when not loaded and 42% of the wheelbase when loaded. Schedule A, Part 2, Category 1, Section 1 replaced: O.I.C. 2010-5, N.S. Reg. 4/2010.

Category 1: Tractor Semi-trailer Section 2 - Weight Limits

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The maximum axle weight limits and maximum gross vehicle weight limits set out in this Section are for axles equipped with dual tires, except for steering axles. The maximum gross vehicle weight limit for a vehicle or combination of vehicles composed of axles equipped with single tires or a combination of single tires and dual tires is the sum of the maximum axle weight limits in Section C–Axle Weight Limits of Part 1–Vehicle Weight and Dimension Limits for the particular axles equipped with single tires or a combination of single tires and dual tires for a specified class of highway. The maximum gross vehicle weight limit of a vehicle or combination of vehicles equipped with single tires or a combination of single and dual tires must not exceed the maximum gross vehicle weight limit of a similar vehicle or combination of vehicles equipped, except for the steering axle, with dual tires for a specified class of highway.

WEIGHT Axle Weight Limits: Steering Axle Single Axle (dual tires) Tandem Axle (including tandem equivalent axle) Axle spread 1.2 m to 1.85 m Axle spread > 1.85 m Tridem Axle (including tridem equivalent axle) Axle spread 2.4 m to less than 3.0 m Axle spread 3.0 m to less than 3.6 m Axle spread 3.6 m to 3.7 m Axle spread greater than 3. 7 m Triaxle Axle

LIMIT Maximum 5500 kg1 Maximum 9100 kg Maximum 18 000 kg Maximum 18 000 kg Maximum Maximum Maximum Maximum

21 24 26 18

000 000 000 000

kg kg kg kg4

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Axle spread 2.4 m to less than 3.0 m Axle spread 3.0 m to less than 3.6 m Axle spread 3.6 m to 4.9 m Gross Vehicle Weight Limits18: Maximum Weight Roads Three axles Four axles–with tandem spread 1.2 m to 1.85 m Four axles–with semi-trailer tandem spread > 1.85 m Five axles–with tandem spreads 1.2 m to 1.85 m Five axles–with semi-trailer tandem spread > 1.85 m Five axles–with tridem spread 2.4 m to < 3.0 m Five axles–with tridem spread 3.0 m to < 3.6 m Five axles–with tridem spread 3.6 m to 3.7 m Five axles–with tridem spread > 3.7 m Five axles–with triaxle spread 2.4 m to < 3.0 m Five axles–with triaxle spread 3.0 m to < 3.6 m Five axles–with triaxle spread 3.6 m to 4.9 m Six axles–with tridem spread 2.4 m to < 3.0 m Six axles–with tridem spread 3.0 m to < 3.6 m Six axles–with tridem spread 3.6 m to 3.7 m Six axles–with tridem spread > 3.7 m Six axles–with triaxle spread 2.4 m to < 3.0 m Six axles–with triaxle spread 3.0 m to < 3.6 m Six axles–with triaxle spread 3.6 m to 4.9 m Intermediate Weight Roads Three axles Four axles–with tandem spread 1.2 m to 1.85 m

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Maximum 18 000 kg2 Maximum 18 000 kg3 Maximum 18 000 kg4 Maximum 23 700 kg Maximum 32 600 kg Maximum 32 600 kg Maximum 41 500 kg Maximum 41 500 kg Maximum 35 600 kg Maximum 38 600 kg Maximum 40 600 kg Maximum 32 600 kg9,11 Maximum 32 600 kg10,12 Maximum 32 600 kg10,13 Maximum 32 600 kg10,14 Maximum 44 500 kg Maximum 47 500 kg Maximum 49 500 kg Maximum 41 500 kg9,16 Maximum 41 500 kg5 Maximum 41 500 kg6 Maximum 41 500 kg7 Maximum 23 700 kg Maximum 32 600 kg

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Four axles–with semi-trailer tandem spread > 1.85 m Five axles–with tandem spreads 1.2 m to 1.85 m Five axles–with semi-trailer tandem spread > 1.85 m Five axles–with tridem spread 2.4 m to < 3.0 m Five axles–with tridem spread 3.0 m to < 3.6 m Five axles–with tridem spread 3.6 m to 3.7 m Five axles–with tridem spread > 3.7 m Five axles–with triaxle spread 2.4 m to < 3.0 m Five axles–with triaxle spread 3.0 m to < 3.6 m Five axles–with triaxle spread 3.6 m to 4.9 m Six axles–with tridem spread 2.4 m to < 3.0 m Six axles–with tridem spread 3.0 m to < 3.6 m Six axles–with tridem spread 3.6 m to 3.7 m Six axles–with tridem spread > 3.7 m Six axles–with triaxle spread 2.4 m to < 3.0 m Six axles–with triaxle spread 3.0 m to < 3.6 m Six axles–with triaxle spread 3.6 m to 4.9 m All Other Highways Three axles Four axles–with tandem spread 1.2 m to 1.85 m Four axles–with semi-trailer tandem spread > 1.85 m Five axles–with tandem spreads 1.2 m to 1.85 m Five axles–with semi-trailer tandem spread > 1.85 m Five axles–with tridem spread 2.4 m to < 3.0 m

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Maximum 32 600 kg Maximum 41 500 kg Maximum 41 500 kg Maximum 35 600 kg Maximum 38 600 kg Maximum 38 600 kg8 Maximum 32 600 kg9,15 Maximum 32 600 kg10 Maximum 32 600 kg10 Maximum 32 600 kg10 Maximum 44 500 kg Maximum 47 500 kg Maximum 49 500 kg Maximum 41 500 kg9,16 Maximum 41 500 kg10 Maximum 41 500 kg10 Maximum 41 500 kg10 Maximum 23 700 kg Maximum 32 600 kg Maximum 32 600 kg Maximum 41 500 kg Maximum 41 500 kg Maximum 32 600 kg9

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Five axles–with tridem spread 3.0 m to < 3.6 m Five axles–with tridem spread 3.6 m to 3.7 m Five axles–with tridem spread > 3.7 m Five axles–with triaxle spread 2.4 m to < 3.0 m Five axles–with triaxle spread 3.0 m to < 3.6 m Five axles–with triaxle spread 3.6 m to 4.9 m Six axles–with tridem spread 2.4 m to < 3.0 m Six axles–with tridem spread 3.0 m to < 3.6 m Six axles–with tridem spread 3.6 m to 3.7 m Six axles–with tridem spread > 3.7 m Six axles–with triaxle spread 2.4 m to < 3.0 m Six axles–with triaxle spread 3.0 m to < 3.6 m Six axles–with triaxle spread 3.6 m to 4.9 m

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Maximum 32 600 kg9 Maximum 32 600 kg9 Maximum 32 600 kg9 Maximum 32 600 kg10 Maximum 32 600 kg10 Maximum 32 600 kg10 Maximum 41 500 kg9 Maximum 41 500 kg9 Maximum 41 500 kg9 Maximum 41 500 kg9 Maximum 41 500 kg10 Maximum 41 500 kg10 Maximum 41 500 kg10

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UNIT 3) Aerodynamics Automotive aerodynamics is the study of the aerodynamics of road vehicles. Its main goals are reducing drag and wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds. For some classes of racing vehicles, it may also be important to produce down force to improve traction and thus cornering abilities. It's unpleasant to think about, but imagine what would happen if you drove your car into a brick wall at 65 miles per hour (104.6 kilometers per hour). Metal would twist and tear. Glass would shatter. Airbags would burst forth to protect you. But even with all the advancements in safety we have on our modern automobiles, this would likely be a tough accident to walk away from. A car simply isn't designed to go through a brick wall. But there is another type of "wall" that cars are designed to move through, and have been for a long time -- the wall of air that pushes against a vehicle at high speeds. Most of us don't think of air or wind as a wall. At low speeds and on days when it's not very windy outside, it's hard to notice the way air interacts with our vehicles. But at high speeds, and on exceptionally windy days, air resistance (the forces acted upon a moving object by the air -- also defined as drag) has a tremendous effect on the way a car accelerates, handles and achieves fuel mileage. This where the science of aerodynamics comes into play. Aerodynamics is the study of forces and the resulting motion of objects through the air. For several decades, cars have been designed with aerodynamics in mind, and carmakers have come up with a variety of innovations that make cutting through that "wall" of air easier and less of an impact on daily driving. Essentially, having a car designed with airflow in mind means it has less difficulty accelerating and can achieve better fuel economy numbers because the engine doesn't have to work nearly as hard to push the car through the wall of air. Engineers have developed several ways of doing this. For instance, more rounded designs and shapes on the exterior of the vehicle are crafted to channel air in a way so that it flows around the car with the least resistance possible. Some high-performance cars even have parts that move air smoothly across the underside of the car. Many also include a spoiler -- also 48


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known as a rear wing -- to keep the air from lifting the car's wheels and making it unstable at high speeds. Although, as you'll read later, most of the spoilers that you see on cars are simply for decoration more than anything else. In this article, we'll look at the physics of aerodynamics and air resistance, the history of how cars have been designed with these factors in mind and how with the trend toward "greener" cars, aerodynamics is now more important than ever.

Vehicle Aerodynamic Factors         

Aerodynamic Forces Laminar Separation Tripping of Boundary Layer Pressure Distribution Wake Tires Glass and Trim General Improvements Unconventional Features

Aerodynamic Forces   

Lift force Drag force Side force

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Effects of aerodynamic forces are profound



Force coefficients

Example o

What is a vehicle‘s drag force, with a frontal area of 1.5 m2, CD of 0.4, and traveling at 30 m/s

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Aerodynamic down force o o o o o





Opposite of lift in direction Uses an inverted airfoil Increases load on tires without increasing the vehicle‘s weight (up to 10% of vehicle‘s weight) Improves cornering performance with no weight penalty First discovered in 1960s!

Example of down force

Example o Rear Spoiler (Mazda RX-7 R-2) o CD = 0.31 (0.29 without spoiler) o CL front = 0.10 (0.16 without spoiler) o CL rear = 0.08 (0.08 without spoiler)

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Underbody improvements o Aerodynamic properties o Reduce drag o Increase down force

Laminar Separation  

Laminar Separation o Flow separation inside the boundary layer Laminar Bubble o Streamlines enclosed within the laminar separation

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VEHICLE CODY ENGINEERING AND SAFETY  

 

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Laminar bubble area is sensitive and can easily separate, resulting in excess drag Can appear in low Re range (104-105), and disappear as speed increases, causing severe discrepancies in flow visualization and analysis

The rear end shape is the most critical factor in lowering the drag coefficient Flow separation above the rear window can cause annoying dirt deposits on the glass

Tripping of Boundary Layer 

 

Introduction of aerodynamic disturbances o Fins o Vortex generators o Strips of coarse sand paper Forcing laminar to turbulent flow Drag reduction due to delay in the onset of flow separation

Pressure Distribution 



Helps the placement of inlets and outlets o Lower pressure at the outlet o Higher pressure at the inlet Favorable pressure distribution 53




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o Prevents flow separation Unfavorable pressure distribution o Promotes flow separation o Promotes turbulent flow within boundary layer



Example of inlet



Radiator inlet configurations

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Wake   

The disturbed air flow left behind the vehicle Usually in the form of a vortex Caused by merging air flows at different velocities near sharp edges

  

Increases drag Presents danger to the following vehicles Can be controlled with small fins or smooth edges

Tires 

Tires influence a vehicle‘s aerodynamic properties o Cross sectional area o Frontal area o Rotation of tires

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Effects of tire rotation

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Effect of all-wheel-steering

Glass and Trim 

Drag can be reduced by making glass and trim as flush with the body as possible

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Elimination of rain gutter improves the vehicle aerodynamics

General Improvements

1- Front spoiler 2- Ducted engine cooling 3- Shrouded windshield wiper arms 4- Aerodynamic mirrors 5- Smooth windshield transitions 6- Smooth side window transitions 7- Smooth rear window transition 58


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8- Optimized trunk corner radii 9- Optimized lower rear panel 10 - Smooth fuel tank and underbody 11- Optimized rocker panels 12- Flush wheel covers 13- Elimination of the rain gutter

Unconventional Features 

Large rear fins promote lateral stability in the 1966 Peugeot CD



1969 Chaparral 2J used auxiliary fans to create suction under the car

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 

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Ford‘s rear mounted transverse engine Fans improve aerodynamic properties and reduce drag

Aerofoil What is an airfoil, and how does it work: An airfoil is a body (such as an airplane wing or helicopter blade) designed to provide a desired reaction force when in motion relative to the surrounding air. There has been much discussion with regards to how and why airfoils really work. The popularly-known explanation (as seen in K-6 textbooks) involves mis-applying Bernoulli‘s principle by stating that high-pressure, low-velocity air on the bottom-side of the airfoil and low-pressure, high-velocity air on the top-side, which recombines at the trailing edge of the airfoil at the same time, regardless of angle-of-attack, is the sole mechanism by which lift is generated. Well, if this is the case, then we would have a really, really tough time trying to explain how airplanes fly upside down:

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The truth is, the top-side air travels significantly faster than the bottomside air. They never recombine

(Velocity field around a wing) Additionally, the image below illustrates, using pressure patterns, that the angle-of-attack indeed has profound effects on the lift that's generated.

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(Pressure patterns at different angle-of-attacks (red shaded regions indicate positive pressure relative to atmosphere, blue shaded regions indicate negative pressure relative to atmosphere) Besides using Bernoulli‘s principles (which accounts for conservation of energy), Newton‘s principles (conservation of momentum), Euler‘s equations (conservation of mass, momentum, and energy), and NavierStokes equations (all of the above plus viscosity) must also be dealt with in order to fully understand the generation of lift. Why put airfoils on cars: Airfoils, when properly mounted at the rear-end of a race car, can generate large amounts of down force. This down force offsets the aerodynamic lift inherent to the car, and in turn increases the amount of tire grip available. This increased tire grip allows the car to carry higher speeds through the corners and out of corner exits. Being able to carry the greatest corner exit speeds is critical to producing the lowest lap times, especially when there are many corners that lead to long straight-aways.

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What to consider when putting airfoils on cars: In application (airfoil on a race car), the key point to understand is to know that the amount of lift an airfoil generates is dependent on many things, including (but not limited to): 1. Angle-of-Attack (AOA). 2. Shape. 3. Size. 4. Position in the air stream. Considerations must be made for all of the above items when designing, installing, and using an airfoil on a race car. 3D airfoils:

(APR Performance GTC series airfoil) A 3D airfoil is an airfoil that has variable airfoil cross section across its span. Most modern aircraft airfoils are 3D airfoils. When a 3D airfoil is designed for use on a production-based race car, the outer sections will typically have much more AOA built-in than the center section. For example, if the center section is set to zero degrees (relative to the ground), then the outer sections may end up at 15 degrees angle (relative to the ground.

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Why and when to use a 3D airfoil (rather than a 2D airfoil):

(Computational Fluid Dynamics (CFD) illustration of airflow around Aston Martin race car) There is a popular notion that, in order for an airfoil to function on a race car, the airfoil needs to be in clean, free-air at or above the rear roofline of the car. This is only a partially-true statement. On cars with solid roofs and sloping rear windows, the air that flows from the rear center edge of the roof will travel downward at an angle toward the airfoil. The problem here is that only the center section of the 2D airfoil will see this downward "push" of air, while the outer section of the 2D airfoil will see much less of this (it will see straighter, freer air). Decreasing the 2D airfoil's angle-of-attack to accommodate for the downward airflow causes the outer sections to produce relatively less down force. Increasing the 2D airfoil's angle-of-attack causes the center section to produce relatively more down force. The 2D airfoil ends up functioning inefficiently in this unbalanced state. This is a situation where the 3D airfoil has an advantage. The 3D airfoil's built-in angle-of-attack variations allow it to function more efficiently when it is mounted below the roofline. When the center section is mounted at 0 degrees angle-of-attack (relative to the ground), it acts as though it has a positive (typically 15 to 20 degrees in a sedan-type car) angle-of-attack relative to the airflow coming from the rear center edge of the roof. The outer sections, with the higher angle-of-attack built-in, are better-suited to take advantage of the cleaner, freer air stream. Therefore, the 3D airfoil, when used in a sedan-type car and mounted below the roofline, is able to function more efficiently (and in a more balanced state) than a 2D airfoil.

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Which type of airfoil is better?

(APR Performance GTC series airfoil for C6 Corvette application) There is not going to be one simple answer to this question. In reality, a better question to ask may be, "which type of airfoil is better for my application?" In some cases, it may be better to use the 2D airfoil. In other cases, it may be better to use the 3D airfoil. In order to find the answer, we must know our intended use and we must consider the following: 1. Type of car (sedan, coupe, hatchback, open-wheel, etc.). 2. Approval of the specific airfoil (type, size, supplier, etc.) for the race series. 3. Mounting-height rules for the race series. Typically, when there is a mounting-height restriction that requires the airfoil to be mounted below the roofline, it will likely be better to use a 3D airfoil. When there is no mounting-height restriction, either 2D airfoil mounted above the roofline or a 3D airfoil mounted below the roofline may

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work.

(Dark Horse racing‘s 2007 SCCA ITO entry) It is definitely not advisable to run a 3D airfoil above the roofline for any type of car. This is especially true with hatchback type cars, where there is no rear deck (or trunk lid) to mount the airfoil to. The initial inclination may be to mount any airfoil on the roof, which would probably be a great idea for a 2D airfoil, but it would definitely be bad idea for a 3D airfoil (the 3D airfoil functions in an unbalanced state when it is in free air). Basic Aerofoil Shapes Overview The four basic categories of airfoil shapes are Reflex, Wright Brothers, Bernoulli, and Modern. To make a reflex wing from a lunch tray, just sand the leading edge and trailing edge enough to round the corners. If you can find a lunch tray that is warped or bent, you can round the leading and trailing edges to make a Wright Brothers wing. To make a symmetrical Bernoulli wing, round the leading edge but sand back about 1/4 to 1/3 of the way back. For the trailing edge, sand along the length of the wing from both the top and bottom. Sand until the trailing edge is a smooth wedge from about half way back on the wing to the trailing edge.

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To make a modern airfoil shape with a lunch tray, round the leading edge. But, just round the bottom edge slightly and round the top edge to 1/4 to 1/3 of the way back. For the trailing edge, sand down just from the top. You can also make a modern wing with a 1/2 inch or 3/4 inch thick piece of pink insulation foam. To sand the trailing edge of a Bernoulli or Modern wing, place the wing blank along the edge of a table. Use the sandpaper and sand lengthwise to achieve your desired wing shape. Use many light passes. Reflex (flat plate) wing The simplest airfoil shape is the flat plate (or reflex). This is easy to make, but it is not very strong. And it is easy to stall. Simple models such as this balsa wood glider use this airfoil. To get any lift, the wing must be tipped up a little bit. To do this, the tail of the glider is angled down causing the nose of the model to tip up. This action is called reflex action, hence the name of this airfoil.

Wright Brothers Wing The relex airfoil stalls easily and does not provide very much lift. To get more lift and to make their wing less likely to stall, the Wright Brothers curved their wing. With a good curve, the wing will get some lift when it is flying straight into the wind. This is a handy thing for a main wing. The Wright Brother's wing shape is also harder to stall and gives more warning of a stall.

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Bernoulli Wing Daniel Bernoulli was a mathematician who lived long before airplanes. He explained that as air (or water) speeds up, the pressure drops. We now call this Bernoulli‘s Principle. As airplanes when from biplanes to monoplanes, the wings needed to get thicker to support the internal structures. As time went on, wings developed a classic shape of a rounded front (leading edge) and tapered back (trailing

edge), like this As air moves past a streamlined shape like this the air speeds up on the top and bottom and the pressure drops. If you tip the wing up a little, the pressure will drop more on the top than the bottom and you will get lift. A Bernoulli wing will not get any lift until you tip it up a little bit. It will then get more lift than the reflex wing. The Bernoulli wing will also resist stalling for a larger angle than a reflex wing. Since the Bernoulli airfoil does not give any lift when it goes straight into the wind, it is just the thing for your tail surfaces, the horizontal and vertical stabilizers. You can also use the Bernoulli wing shape for your main wing. "Modern" Airfoil Shape To get lift when going straight into the wind and good stall resistance, combine the Wright Brother's wing and the Bernoulli wing into the Modern 68


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wing airfoil shape.

Aerofoil Theory Aerofoil are streamline shaped wings which are used in airplanes and turbo machinery. These shapes are such that the drag force is a very small fraction of the lift. The following nomenclatures are used for defining an aerofoil

Fig 23.4

Aerofoil Section 69

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The chord (C) is the distance between the leading edge and trailing edge. The length of an aerofoil, normal to the cross-section (i.e., normal to the plane of a paper) is called the span of a aerofoil. The camber line represents the mean profile of the aerofoil. Some important geometrical parameters for an aerofoil are the ratio of maximum thickness to chord (t/C) and the ratio of maximum camber to chord (h/C). When these ratios are small, an aerofoil can be considered to be thin. For the analysis of flow, a thin aerofoil is represented by its camber.

The theory of thick cambered aerofoils uses a complex-variable mapping which transforms the inviscid flow across a rotating cylinder into the flow about an aerofoil shape with circulation. Generation of Vortices Around a Wing 

 



The lift around an aerofoil is generated following KuttaJoukowski theorem. Lift is a product of ρ , and the circulation

.

When the motion of a wing starts from rest, vortices are formed at the trailing edge. At the start, there is a velocity discontinuity at the trailing edge. This is eventual because near the trailing edge, the velocity at the bottom surface is higher than that at the top surface. This discrepancy in velocity culminates in the formation of vortices at the trailing edge. Figure 23.6(a) depicts the formation of starting vortex by impulsively moving aerofoil. However, the starting vortices induce a counter circulation as shown in Figure 23.6(b). The circulation around a path (ABCD) enclosing the wing and just shed (starting) vortex must be zero. Here we refer to Kelvin's theorem once again.

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Fig 23.6

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

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Vortices Generated when an Aerofoil Just Begins to Move

Initially, the flow starts with the zero circulation around the closed path. Thereafter, due to the change in angle of attack or flow velocity, if a fresh starting vortex is shed, the circulation around the wing will adjust itself so that a net zero vortices is set around the closed path. Real wings have finite span or finite aspect ratio (AR) λ , defined as

Where b is the span length, As is the plan form area as seen from the top.. 

For a wing of finite span, the end conditions affect both the lift and the drag. In the leading edge region, pressure at the bottom surface of a wing is higher than that at the top surface. The longitudinal vortices are generated at the edges of finite wing owing to pressure differences between the bottom surface directly facing the flow and the top surface.

Fig 23.7

Vortices around a Finite Wing

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Heave Pitch, Roll, Warp and Yaw -In order to study the response of the car to control inputs or disturbances, it is necessary to combine more than one coordinate system to fix the position of the components in space. The convention for the complete car has been taken from aeronautics with an Earth-Fixed axis system XYZ as shown in the diagram.

The car has its own axis notation xyz. the suspension pick up points related to a z axis O-Line plane for the base of the chassis (this may not be the lowest point on the car). The x axis often points rearwards and is normally related to a front bulkhead. The y axis is lateral from the centre line. Note that the z axis origin is not at the ground plane, and there is no rake to the z plane. These coordinates must be related to the Earth-Fixed system before handling analysis can take place.

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Yaw The yaw allows the vehicle to move towards the left or right while in motion. The movement is done about a vertical axis Pitch The pitch refers to the movement of the vehicle‘s nose either up or down. Roll Roll is known as the rising or dipping of the vehicle. HOW TO CALCULATE AERODYNAMIC DRAG COEFFICIENT The drag coefficient

is defined as:

where: is the drag force, which is by definition the force component in the direction of the flow velocity, is the mass density of the fluid, is the speed of the object relative to the fluid and is the reference area.

Fd is the force on the vehicle due to air resistance (drag) in Newtons Frr is the force on the vehicle due to rolling resistance in Newtons F is the total force on the vehicle in Newtons V is the vehicle‘s velocity in m/s a is the vehicle‘s acceleration in m/s2 A is vehicle frontal area in m2 M is vehicle mass including occupants in kg rho is the density of air which is 1.22 kg/m3 at sea level g is the gravitational acceleration constant which is 9.81 m/s2 Cd is the vehicle‘s drag coefficient we want to determine Crr is the vehicle‘s coefficient of rolling resistance we want to determine 74


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Now for some formulas: Fd = -Cd*A*0.5*rho*V2 (formula for force due to air resistance or drag) Frr = -Crr*M*g (formula for force due to rolling resistance) F = Fd + Frr (total force is the sum of Fd and Frr) F = M*a (Newton‘s second law) Note that both Fd and Frr are negative indicating that these forces act opposite to the direction of the velocity. Note also that Fd is increases as the square of velocity. This is why driving at high speeds is much less efficient than driving at low speeds. Combining these formulas with a bit of algebra gives us the acceleration due to air and wind resistance as a function of velocity: a = -(Cd*A*0.5*rho*V2)/M – Crr*g

Wind tunnel testing Automotive Wind Tunnel The Automotive Wind Tunnel Emmen (AWTE) infrastructure is specifically dedicated to the development of race and production cars up to 50% size. The wind tunnel is equipped with a rolling road system and a multi axis model manipulator for modeling ride height, yaw, roll and steering conditions. The ultimate aerodynamic optimization can be achieved by the use of the dynamic shaker system in combination with time dependent acquisition for in stationary driving behavior. RUAG customers can count on state of the art infrastructure, motivated employees, and efficient testing. Maximum airspeed Test section size Test section length Reynolds number

50 m/s 180 km/h 2.5 x 1.5 meter 3.8 x 1.8 meter 4 x 106

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RACE CAR AERODYNAMICS The aerodynamics of the race car is multi-functional. The first purpose is to make it as streamline as possible. The second purpose is to provide downforce for the race vehicle. The last reason is to control the airflow over the car‘s body.

This is a computer generate red image of the airflow over the cars' body. Streamlining a vehicle means reducing the drag of the vehicle traveling through the air. This is done two ways: one is making the surfaces in contact with the air as smooth as possible. The second way is decreasing the size of the car. This is due to the fact that DRAG = ½DρAυ²; where D is a drag coefficient (which is dependent on the smoothness 76


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of the material), ρ is the density of air, υ is the velocity traveling through the air, and A is the cross-sectional area of the vehicle. By reducing the cross-sectional area of the vehicle, vehicles can have less drag and in turn drive faster. As mentioned before, the drag coefficient is related to how smooth the material is that the air is traveling over. DRAG = ½DρAυ²

Photo courtesy: Ferrari / Shell racing

Down force is the opposite of lift. This is the result of Bernoulli‘s effect. Bernoulli‘s effect explains how fluids, in this case the air, will react when traveling over the wing surface. Lift occurs due to a difference in pressures on opposite sides of airfoils caused by this effect. The wings on race cars are essentially wings flipped upside-down so that the lifting force is directed in a downward direction. This is downforce. The theory behind creating downforce is to increase the force the vehicle has on the ground. This in turn will increase the traction of the tires, enabling the race cars to make sharp corners at higher speeds. Most race cars create so much downforce that at speeds greater than 100 mph they have enough downforce that they could drive on a road that was up-side down.

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Photo courtesy: Mclaren / Mercedes Benz racing By controlling the airflow over the car‘s body, designers can direct more air to those components that need it most. For example, most cars have vents located on the inside of tires to direct air over the brake discs and brake calibers. This helps keeping the brakes cool therefore making them more effective. Designers also try to direct more air to the cooling and powering of the engines. By increasing the airflow to these components, mainly the engine‘s radiators, turbo chargers, and intakes, they can make the car more powerful and faster. 1991 Nissan NPT-90 GTP

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High down force configuration: Single ride height point, FRH: 2.0" RRH: 2.5" Down 4539 6536 8069

force: lbs. @ 150 mph, with 893 lbs. of drag lbs. @ 180 mph, with 1286 lbs. of drag lbs. @ 200 mph, with 1588 lbs. of drag

Lift-to-drag ratio: 5.08:1

Bluff Body AEROCYNAMICS

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- Pressure drag or form drag which is based on the pressure difference between the upstream and downstream surfaces of the object - Skin Friction which results from the viscous shear of the fluid flowing over the object surfaces. The form drag is the resultant of resolved forces normal to the surface of the object and the skin-friction is the resultant of resolved forces tangential to the surface. The total drag on an object is called the profile drag and is the sum of the pressure and skin-friction drag when the drag is primarily viscous drag, the body is streamlined, and when the drag force is primarily pressure drag the body is called a bluff body. A perfect fluid flowing past an infinitely long cylinder is represented as streamlines which are arranged such that the flow through each streamline is fixed at Q . The streamlines flow over the cylinder and all forces are balanced front/back and top /bottom and there is therefore no form drag. A perfect fluid cannot transfer shear stress so there is no viscous drag. In real fluids there is a pressure build up on the front surface as the fluid is slowed and the streamlines are re directed round the cylinder. As the fluid flows over the cylinder the fluid separates into a wake which is a lower pressure region. There is therefore significant form drag. There is also skin-friction drag as the fluid passes over the surface.

If the cylinder rotates, as shown below, the drag between the surface and the fluid results in the fluid flow as shown. The flow results in higher fluid velocities above the cylinder compared with the flow below the cylinder . Application of bernoulli's equation results a lower pressure above the cylinder and a consequent lift.

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UNIT4) LOAD DISTRIBUTION Introduction The automotive chassis provides the strength necessary to support the vehicular components and the payload placed upon it. The suspension system contains the springs, the shock absorbers, and other components that allow the vehicle to pass over uneven terrain without an excessive amount of shock reaching the passengers or the cargo. The steering mechanism is an integral portion of the chassis, as it provides the operator with a means of controlling the direction of travel. The tyres grip the road surface to provide good traction that enables the vehicle to accelerate, brake, and make turns without skidding. Working in conjunction with the suspension, the tyres absorb most of the shocks caused by road irregularities. The body of the vehicle encloses the mechanical components and passenger compartment. It is made of relatively light sheet metal or composite plastics. The components which make up the chassis are held together in proper relation to each other by the frame. Frames The seperate frame and body type of vehicle construction (image 1 and 2) is the most common technique used when producing most full-size and cargo vehicles. In this type of construction, the frame and the vehicle body are made seperately, and each is a complete unit by itself. The frame is designed to support the weight of the body and absorb all of the loads imposed by the terrain, suspension system, engine, drive train, and steering system, ad the body merely contains and, in some cases, protects the cargo. The body generally is bolted to the frame at a few points to allow for flexure of the frame and to distribute the loads to the intended load-carrying members. The components of this type of frame are as follows: The SIDE MEMBERS or rails are the heaviest part of the frame. The side members are shaped to accomodate the body and support the weight. They are narrow toward the front of the vehicle to permit a shorter turning radius for the wheels and then widen under the main part of the body where the body is secured to the frame. Trucks and trailers commonly have frames with straight side members to accomodate several designs of bodies and to give the vehicle added strength to withstand heavier loads. The CROSS MEMBERS are fixed to the side members to prevent weaving and twisting of the frame. The number, size and arrangement of the cross members depend on the type of vehicle for which the frame was designed. Usually, a front cross member supports the radiator and the front of the engine. The rear cross members furnish support for the fuel tanks and rear trunk on passenger cars and the tow bar connections for trucks. Additional 82


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cross members are added to the frame to support the rear of the engine or power train components. The GUSSET PLATES are angular pieces of metal used for additional reinforcement on heavy-duty truck frames. With this type of frame construction, the body structure only needs to be strong and rigid enough to contain the weight of the cargo and resist any dynamic loads associated with cargo handling and cargo movement during vehicle operation and to absorb shocks and vibrations transferred from the frame. In some cases, particularly under severe operating conditions, the body structure may be subjected to some torsional loads that are not absorbed completely by the frame. This basically applies to heavy trucks and not passenger vehicles. In a typical passenger vehicle, the frame supplies approximately 37 percent of the tensional rigidity and approximately 34 percent of the bending rigidity; the balance is supplied by the body structure. The most important advantages of the separate body and frame construction are as follows:    



Ease of mounting and dismounting the body structure. Versatility; various body types can be adapted to a standard truck chassis. Strong, rugged designs are achieved easily; however, vehicle weight is increased. Isolation of noise generated by the drive train components from the passenger compartment through the use of rubber mounts between the frame and the body. Simplistic design that yields a relatively inexpensive and easy manufacturing process. Frame members serve as supports to which springs, independent suspensions, radiators, or transmissions may be attached. Additional brackets, outriggers and engine supports are added for the mounting of running boards, longitudinal springs, bumpers, engines, towing blocks, shock absorbers, fuel tanks, and spare tyres.

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Image 1 - Separate Frame and Body

Image 2 - Components of a typical Frame Design Integrated Frame and Body (Monocoque) The integrated frame and body type of construction (image 3) also referred to as unitized construction, combines the frame and body into a single, one84


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piece structure. This is done by welding the components together, by forming or casting the entire structure as one piece, or by a combination of these techniques. Simply by welding a body to a conventional frame, however, does not constitute an integral frame and body construction. In a truly integrated structure, the entire frame-body unit is treated as a loadcarrying member that reacts to all loads experienced by the vehicle-road loads as well as cargo loads. Integrated-type bodies for wheeled vehicles are fabricated by welding preformed metal panels together. The panels are preformed in various loadbearing shapes that are located and oriented so as to result in a uniformly stressed structure. Some portions of the integrated structure resemble frame like components, while others resemble body like panels. This is not surprising, because the structure must perform the functions of both of these elements. An integrated frame and body type construction allows and increases in the amount of noise transmitted into the passenger compartment of the vehicle. However, this disadvantage is negated by the following advantages:    

Substantial weight reduction, which is possible when using a well-designed unitized body. Lower cargo floor and vehicle height. Protection from mud and water required for driveline components on amphibious vehicles. Reduction in the amount of vibration present in the vehicle structure.

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Image 3 - Integrated Frame and Body Ladder Frame (Truck Frame) The truck frame (image 4) allows different types of truck beds or enclosures to be attached to the frame. For larger trucks, the frames are simple, rugged, and of channel iron construction. The side rails are parallel to each other at standardized widths to permit the mounting of stock transmissions, transfer cases, rear axles, and other similar components. Trucks that are to be used as prime movers have an additional reinforcement of the side rails and rear cross members to compensate for the added towing stresses.

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Image 4 - Ladder Frame (Truck Frame) Frame Maintenance Frames require little, if any, maintenance. However, if the frame is bent enough to cause misalignment of the vehicle or cause faulty steering, the vehicle should be taken off of the road. Drilling the frame and fish plating can temporarily repair small cracks in the frame side rails. Care should be exercised when performing this task, as the frame can be weakened. The frame of the vehicle should not be welded by gas or arc welding unless specified by the manufacturer. The heat removes temper from the metal, and, if cooled too quickly, causes the metal to crystallize. Minor bends can be removed by the use of hydraulic jacks (also known as a portal-power image 5), bars and clamps.

Image 5 - Body Repair tool, Porte-Power

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UNIT 5) BODY FITTINGS AND INTERIOR CONTROLS Window winding Mechanism

There are three basic systems used to raise and lower car windows: mechanical linkage with scissor action; cable and pulley; or rack and pinion. No two manufacturers use exactly the same design for window-lifting systems of the same basic type. Details vary from car to car. If you need to fit a new mechanism because of accident damage, breakage or wear on the old one, obtain the correct replacement from the spares department of a main dealer for the car. Renewing a link-type mechanism Fully close the window and tape the glass to the top of the window frame. Use strong tape, as this must hold the glass to prevent it dropping when the mechanism is removed. Take off the door fittings and trimmings and the inner door panel. Carefully remove the polythene condensation-barrier sheet behind the panel and set it aside for reuse. Undo and remove the screws holding the toothed regulator to the door frame and put them in a safe place. Push the regulator into the door interior. Reach through the door access aperture to disconnect the sliding arm. It may fit into a bottom channel, or it may be held by a centre pivot secured by three screws. After disconnecting the sliding arm, move the regulator and the arm sideways in both directions until the upper end comes away from the sliding channel at the bottom of the glass. Lift out the mechanism through the access aperture.

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Renewing a link-type window mechanism

Mechanical linkage for lifting and lowering the window glass includes a sliding arm that operates by scissor action. Before fitting the new mechanism, grease the pivot and sliding bearings and the gear teeth on the regulator. Lightly smear the whole mechanism with petroleum jelly which will act as a protection against rust. To refit the new assembly, which includes the regulator and sliding arm, follow the removal procedure in reverse. Retape the polythene sheet in position. Test the mechanism before refitting the door panel and trim. Adjusting a cable-and-pulley system The cable may slacken after long use, causing play in the winder mechanism as the handle changes direction between up and down. Adjusting a pulley to take up the slack in the cable will correct the fault. Take off the door fittings and trimmings and the inner door panel, including the polythene condensation-barrier sheet (See SHEET 65). Check the condition of the cable; even if it is only slightly frayed, it must be renewed. If not frayed, it can be adjusted. Look for the adjustable pulley, which slides sideways on a mounting in the door frame to alter the cable tension. Loosen the pulley mounting and move it to take up the slack in the cable. Retighten the mounting and check that the winder action is smooth. If

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necessary, readjust the pulley until it is. Take care not to over-adjust, which will strain the cable and regulator. If the cable is broken or frayed and needs renewing, you will probably have to buy it as part of a complete assembly with a new regulator. There are different assemblies for right-hand doors and left-hand doors. Make sure you buy the correct one.

To fit a new cable, take the cable clamps off the bottom of the window glass, push the window closed, and tape it to the top of the frame. Undo the fixing screws to remove the regulator and cable drum, and the cable. Slacken the adjustable pulley. Screw the new regulator and its loop of cable in position. To wind the cable on to the grooves of the cable drum, take the length fixed to the drum on the side nearest to the middle of the car. Loop it round the furthest bottom pulley. Fit the winder to the regulator and drum. Keeping the cable taut, wind it on to the drum. Turn the winder anti-clockwise on a right-hand door, clockwise on a left-hand door.

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Take care that the spare part of the cable does not wrap round the drum, and wind until all the grooves in the drum are filled and the upper part of the cable is vertical. Keeping the cable taut, loop it round the rear upper pulley, the front lower pulley, and the front upper pulley. Make sure it does not kink. Tension the cable by moving the adjustable pulley. Oil the pulley spindles with engine oil, and grease the cable. To re-attach the window glass to the mechanism, wind the cable fully down, then up again one full turn of the winder. Some regulators have an indicator to mark the point. UN tape the glass, lowers it fully and re-clamp it to the cable.

Window regulator using rack-and-pinion system. Test the winding action several times. If the glass does not move up and down smoothly, reposition it on the cable until it does. Replace the polythene sheet and refit the door panel and trim. Replacing a rack-and-pinion system Take off the door fittings and trimmings and the inner door panel, including the polythene condensation-barrier sheet. Wind the window down until you can undo the plate holding the glass to the rack. Push the glass to the top of the frame and secure it with tape. To remove the rack, undo the screws at its top and bottom and at the winder-handle boss. 91


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The bottom screws of the rack may be on the underside of the door. Lift out the rack and winder boss through the access aperture. Grease all the moving parts of the new rack assembly before fitting. Position the handle-fixing holes on the boss to align with the winder handle. Refit the handle and wind the mechanism fully down. Untape the glass and refit it on the rack. Check that the glass moves smoothly up and down. If not, adjust its position on the rack until it does.

Door lock mechanism

Inside a Car Door In this car, the power-door-lock actuator is positioned below the latch. A rod connects the actuator to the latch, and another rod connects the latch to the knob that sticks up out of the top of the door. When the actuator moves the latch up, it connects the outside door handle to the opening mechanism. When the latch is down, the outside door handle is disconnected from the mechanism so that it cannot be opened.

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Inside a car door To unlock the door, the body controller supplies power to the door-lock actuator for a timed interval.

This actuator can move the metal hook shown in this photo to the left or right. When mounted in the car, it is vertical, so the hook can move up or down. It mimics your motions when you pull the knob up or push it down. Inside the Actuator The power-door-lock actuator is a pretty straightforward device.

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Inside the power-door-lock actuator This system is quite simple. A small electric turns a series of spur gears that serve as a gear reduction. The last gear drives a rack-and-pinion gear set that is connected to the actuator rod. The rack converts the rotational motion of the motor into the linear motion needed to move the lock. One interesting thing about this mechanism is that while the motor can turn the gears and move the latch, if you move the latch it will not turn the motor. This is accomplished by a neat centrifugal clutch that is connected to the gear and engaged by the motor.

Centrifugal clutch on the drive gear When the motor spins the gear, the clutch swings out and locks the small metal gear to the larger plastic gear, allowing the motor to drive the door latch. If you move the door latch yourself, all of the gears will turn except for the plastic gear SOME INTERIOR MECHANISMS OF AN AUTOMOBILE             

Instrumentation Steering Wheel Ignition Accelerator Brakes Gearshift Clutch Horn Mirrors Lights Turn Signals Hazard Lights Windshield Wipers

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Instrumentation

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In order to be able to operate your vehicle safely, you must know the functions and locations of all the interior mechanisms of your car.

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Warning lights are provided on your car's instrument panel. They light up in case of a serious problem. There are three kinds of warning lights:   

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The instrument panel contains gauges which include the following: 

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Speedometer, which indicates speed in both miles and kilometers per hour Tachometer, which indicates rotations in the engine in revolutions per minute (RPMs) Odometer, which indicates the total number of miles your car has been driven since it was manufactured

Fuel gauge, which shows the fuel level in your car's fuel tank Oil gauge, which shows oil level

Oil Pressure Warning Light Temperature Warning Light Battery Low Warning Light

Temperature Warning Light/Gauge: this light goes on when the engine temperature or the radiator's coolant is too hot. In some vehicles, a gauge is used that would show the needle in the warning zone of HOT. If this warning light comes on while driving, STOP as soon as you can at a safe place and shut the engine off. Never remove the radiator cap to check the coolant level when the engine is hot. The coolant is at boiling temperature and under pressure. If the cap is released, the hot coolant will release with pressure and can cause severe burns if you are standing too close. 95


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Oil Pressure Warning Light: this light goes on when the engine oil is not circulating at the required pressure. Some vehicles have an oil pressure gauge that reads LOW when the engine's oil pressure is too low. If you see an oil pressure warning while driving, STOP immediately at a safe place and turn off the engine.

The steering wheel is located directly in front of the driver‘s seat. Turning the steering wheel transmits force, which turns the wheels to determine the direction of travel.

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Battery Low Warning Light: when this light goes on or the battery gauge reads LOW, this means that the battery power is running out.

Steering Wheel

Most vehicles today have power steering, which makes turning the wheel relatively easy. If you have power steering and find it necessary to exert a lot of physical force to turn your wheel, you should probably take your car to a mechanic.

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the dashboard instruments to activate. The final position causes your engine to start.

Ignition

Accelerator

` The ignition is located either on the side of the steering column or on the dashboard. It is a multifunction switch, into which you insert your key, in order to energize the electrical circuits and activate your starter motor.

The accelerator is also known as gas pedal. It is the pedal located on the floor on the far-right. This pedal controls the amount of gas being fed into the engine and thereby controls the speed of the vehicle. You push the accelerator with your right foot with your heel resting on the ground. Do not be jerky with the accelerator. Rather, push it gradually while your car speeds up.

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Brakes

Ignitions usually have three positions which serve different purposes. You turn your key clockwise to go to a higher position and counter-clockwise to deactivate it. The first position is the off position when your car is in park. The second position causes 97


The brake pedal is located on the floor to the left of the accelerator. When pressed, it applies the brakes, causing the vehicle to slow down and/or stop. You must use your right foot (with your heel on ground) to exert force on the pedal to cause the brakes to engage. If your vehicle has standard brakes, the pedal will move a little bit before it resists. If you have power brakes, you do not need to exert as much pressure on the pedal to use the brakes.

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Gearshift

If your car has an automatic transmission, the gearshift is located either on the steering column or on the console between the front seats. The gearshift is used to move a vehicle forward, in reverse, or remain in neutral.

The parking brake can be either a pedal operated by your left foot, a lever under the dashboard, or a lever to the right on the floor. It applies brakes to keep the car from moving when parked or to slow the car down if the regular brakes fail. 

On cars with a manual transmission, the gearshift is actually a stick shift. You must learn to synchronize your gear shifting with pushing the clutch pedal.

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The horn is usually located in the center of your steering wheel. Make sure your horn is fully functioning and can be heard at a distance of 100-200 ft. Do not use your horn excessively. Only use it to communicate with other drivers when necessary or as a warning to others.

Clutch

The clutch pedal is found only in cars with manual transmission. The clutch pedal is located on the floor to the left of the brake pedal. When pressed, it disengages the clutch which eliminates the transmission of power from the engine to the transmission. When released, it smoothly applies power through to the transmission. The clutch must be operated with your left foot, again, with your heel resting on the ground. 

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Horn

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Mirrors

Your car is equipped with both rearview and side mirrors. Make sure that your mirrors are properly adjusted before you begin driving. The rearview mirror is located at the top center of your windshield. It is shaped like a rectangle and allows you to see what is happening behind you.

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vehicle has these fixtures in place and that they are fully functioning.

The side mirrors are located on the exterior side of your vehicle and allow you to view periphery traffic.

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Lights

Lights are significant because they allow you to see your surroundings, give others a way to see you, and give other drivers indications of your future actions. Cars are required to have certain lighting fixtures, and these generally have luminosity regulations. Make sure that your

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Vehicles must be equipped with low-beam as well as high-beam headlights. Low-beams must be turned on when it gets dark or in any moment of low visibility due to bad weather. Most states (e.g., Alaska, Michigan, Nevada, Texas, and Utah) require that lights must be turned on from one-half hour after sunset until one-half hour before sunrise. Other states, (e.g., Arizona, Virginia) require that lights are turned on from sunset to sunrise. Consult your state's Drivers Handbook for details.

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by law that if you turn on your wipers you must also turn on your lights.

High-beams are also located at the front of your vehicle and have a higher luminosity that covers greater distance. High-beams are to be used in times of very low visibility. However, you are not to use high-beams in fog, for they will only reflect the dampened air and blind other drivers.

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side of the road. Most of the states require that you switch to lowbeams 500 ft. or more from oncoming vehicles. Consult your state's Drivers Handbook for details. The switch for headlights varies between vehicles. Consult your car's owner manual to make sure you know exactly how to turn your headlights on.

Each vehicle must also have taillights and brake lights. Most of the states require that the taillights be visible from 500 ft. Taillights are red and are located on the back of your vehicle. Brake lights light up when you hit brakes to signal the drivers behind you to stop.

High-beams are to be turned off when another vehicle is in front of you or approaching on the opposite 101


Parking lights are located at the front and back of your vehicles; they are white or amber in the front and red on the back. All of them must be visible for 500 ft. It is never legal to drive with your parking lights on; they are only to be used during parking.

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Turn Signals Your car is equipped with turn signal lights on its four corners. On the inside of your car, these turn signals usually appear as green arrows facing the direction of the intended turn.

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Hazard Lights

Your hazard lights warn other drivers of an emergency situation you may be encountering. All four turn signal lights come on when you activate your hazard lights. Again, consult your car owner's manual for the exact location of the hazard lights switch/button in your vehicle.

Windshield Wipers

On most cars, the turn signal lever is located to the left of the steering wheel. Shifting the lever up indicates a right turn and shifting it down indicates a left turn. Your turn signal should turn off after a turn or a lane change, but if it does not, you should turn it off manually, as soon as possible.

On most vehicles, the windshield wipers can be activated by a lever located to the right of the steering wheel. Usually, you can adjust the speed of your wipers to optimize performance for specific driving conditions. 102

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In transport, driver visibility is the maximum distance at which the driver of a vehicle can see and identify prominent objects around the vehicle. Visibility is primarily determined by weather conditions and by a vehicle's design. The parts of a vehicle that influence visibility include the windshield, the dashboard and the pillars. Good driver visibility is essential to safe road traffic.

Wiring A car's wiring has to distribute power from the battery to devices located all over the car. It also has to transmit data on a data bus, as well as a variety of digital and analog signals from switches and sensors. This means that there are many different types of wires in your car. Some wires that transmit signals from switches or sensors carry almost no current. Those that provide power to large electric motors carry lots of current.

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If too much current goes through a wire, it can overheat and melt. The amount of current that a wire can handle depends on its length, composition, size and how it is bundled. Let's quick look at SAFETY how each of these properties M affects theSIDDIQUI wire's current-carrying VEHICLEtake CODY a ENGINEERING AND A QADEER capacity: 

Length - Each type of wire has a certain amount of resistance per foot -- the longer the wire, the larger the resistance. If the resistance is too high, a lot of the power that flows down the wire will be wasted; the energy lost as heat builds up in the wire. Ultimately, heat build-up limits the current-carrying capacity of the wire, as the temperature must not get hot enough to melt the insulation.

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Composition - Automotive wire is usually composed of fine copper strands. Generally, the finer the strands, the lower the resistance and the more current the wire can carry. The type of copper used has an effect on the resistance of the wire, too.

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Wire gauge - The wire gauge, or size of the wire, also determines how much resistance the wire has. The larger the wire, the less resistance. The smaller the gauge, the larger the wire -so a 16-gauge wire is bigger than a 24-gauge wire. Wire gauges go all the way down to zero, which is also called 1/0 (one aught). Even bigger than 1/0 is 00 (2/0, or two aught), and so on. The diameter of a 4/0 (four aught) wire is almost half an inch (1.27 cm).

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Bundling - The way a wire is bundled affects how well it can dissipate heat. If the wire is in a bundle with 50 other wires, it can carry a lot less current than if it were the only wire in the bundle. Fuses The main job of the fuse is to protect the wiring. Fuses should be sized and located to protect the wire they are connected to. If a device like your car radio suddenly draws enough current to blow the fuse, the radio is probably already toast. The fuse is there to protect the wire, which would be much harder to replace than the radio. Most cars have two fuse panels. The one in the engine compartment holds the fuses for devices like the cooling fans, the anti-lock brake pump and the engine control unit -- all of which are located in the engine compartment. Another fuse panel, usually located in the dashboard near the driver's knees, holds fuses for the devices and switches located in the passenger compartment.

Interior fuse panel We saw in the last section how the heat build-up in the wire depends on the resistance and the amount of current flowing through the wire. Fuses are really just a special type of wire in a self-contained connector. Most automotive fuses today have two blade connectors and a plastic housing that contains the conductor. There are also some fuses that are in the wiring of the car, called fusible links.

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An assortment of automotive fuses The conductor inside the fuse is made of a metal similar to solder. It has a lower melting point than the wire itself. The size of the conductor is calibrated very carefully so that when the rated current is reached, enough heat is generated to melt the conductor and so break the circuit. When a fuse is blown, it must be replaced before the circuit will work. A blown fuse must be replaced with a fuse of the same amperage. Checking Fuses The most foolproof way to check a fuse is to pull it out of its receptacle and hook up a continuity tester to both blades of the fuse. But if you do this while the fuse is plugged in, you could get continuity through a path other than the fuse (for instance, both sides of the wire may be grounded when you check the fuse). You can usually tell if a fuse is blown by a visual inspection:

Connectors

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Connectors are critical to today's cars. Without them, it would be nearly impossible to build or service a car. Whenever a bundle of wires passes through or attaches to a component of the car CODY that ENGINEERING might haveAND to SAFETY be removed, there must be a M connector there to allow for that removal. VEHICLE A QADEER SIDDIQUI A single connector can have more than 100 wires. In the past, unreliable connectors have been the source of many electrical problems. Connectors have to be waterproof (modern connectors have several seals to keep out moisture), corrosion proof and provide good electrical contact for the life of the vehicle. The connector pictured below is an eight-terminal connector -- it connects eight wires to each other.

The parts of a typical automotive connector: Everything on the left connects to everything on the right. To make this connection, there are a total of 23 separate parts. The main parts are: 

The shell

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The pins and sockets

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The pin retainer

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The seals The Shell The shell is an intricate piece that has a complicated shape. There is a locking clip on the outside that holds the two halves of the connector together. There are holes for the pins, and there are special barbs that lock the pins in place once they are inserted. There are numerous grooves to hold seals and make sure things fit together tightly. All of these features are molded into the piece when it is made. The Pins and Sockets The pins and sockets are responsible for conducting electricity from one half of the connector to the other. These are made very precisely so that the pins and sockets fit together with just enough force to ensure a good connection, but not enough force to make connecting and disconnecting too difficult.

A socket (left) and a pin (right)

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The pins are crimped to the wires using a special crimping tool. Part of the pin wraps around the bare wire, while another part clamps onto the insulation. This makes it harder to pull the wireCODY away from theAND pin. VEHICLE ENGINEERING SAFETY M A QADEER SIDDIQUI The Pin/Socket Retainer The pin/socket retainer is a piece of plastic that slides into the connector from the front. It wedges against all of the plastic locking barbs so they can't release. This piece makes it nearly impossible for the pins and sockets to work their way loose.

The retainer keeps the pins and sockets in place. The Seals The seals prevent water from entering the connection once the connectors are locked together. Each connector has a rubber seal through which all of the wires are fed. This seal fits firmly into the back of the connector. One side of each connector has a round seal that keeps water from entering the space between the connectors once they are locked together.

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BODY CONTROL SYSTEM

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UNIT7) VANS TRUCKS AND BUSES A coach (also motor coach, often simply called a bus) is a type of bus used for conveying passengers on excursions and on longer distance intercity bus service between cities—or even between countries. Unlike transit buses designed for shorter journeys, coaches often have a luggage hold separate from the passenger cabin and are normally equipped with facilities required for longer trips including comfortable seats and sometimes a toilet. The term 'coach' was previously used for a horse-drawn carriage designed for the conveyance of more than one passenger, the passengers' luggage, and mail, which is covered for protection from the elements. The term was applied to railway carriages in the 19th century, and later to motor coaches (buses). Coaches, as they hold passengers for significant periods of time on long journeys, are designed for comfort. They vary considerably in quality from country to country and within counties. Higher specification vehicles include luxury seats and air conditioning. Coaches typically have only a single, narrow door, as an increased loading time is acceptable due to infrequent stops. Some characteristics include: Comfortable seats that may include a folding table, armrests, and recliner. Comfort is considered to be an important feature in coaches. Luggage racks above the seats where passengers can access their carry-on baggage during the journey Baggage holds, accessed from outside the vehicle, often under the main floor or at the rear, where passengers' luggage can be stowed away from the seating area Passenger service units, mounted overhead, on which personal reading lights and air conditioning ducts can be controlled and used by individual passengers with little disturbance to other passengers On-board rest rooms fitted with chemical toilets, hand basins and hand sanitizer. On some buses, on-board entertainment including movies may be shown to passengers On-board refreshment service or vending machines Wheelchair accommodation, possibly including a wheelchair lifts for access. SINGLE DECKER BUS - A single-decker bus or single-decker is a bus that has a single deck for passengers. Normally the use of the term single-decker refers to a standard twoaxled rigid bus, in direct contrast to the use of the term double-decker bus, which is essentially a bus with two passenger‘s decks and a staircase. These types of single-deckers may feature one or more doors, and varying internal combustion engine positions. In regions where double-deckers are not common, the term single-decker may lack common usage, as in one sense, all other main types of bus have a single deck. Also, the

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term may become synonymous with the name transit bus or related terms, which can correctly be applied to double-deckers too. the exception regions of major double deck orQADEER articulated VEHICLEWith CODY ENGINEERING AND of SAFETY MA SIDDIQUIbus operation, usually urban areas, the single Decker is the standard mode of public transport bus travel, increasingly with low floor features. With their origins in van chassis, minibuses are not usually considered single-deckers, although modern minibus designs blur this distinction. Minibuses can also be regarded as both included with and separate from standard single-deckers, in terms of full size length and vehicle weights, although again design developments have seen this distinction blurred. Some coach style buses that do not have under floor luggage space can also be correctly termed as single-deckers, with some sharing standard bus chassis designs, such as the Volvo B10M, with a different body style applied. DOUBLE DECKER BUSA double-decker bus is a bus that has two storeys or decks. Red double-decker buses are used for mass transit in London. Double-decker buses are also used in other cities in Europe, Asia, and former British colonies and protectorates such as Hong Kong, Singapore and Canada. Almost all double-deckers have a single, rigid chassis. This type of bus is often used for touring rather than for mass transit. As William Ewart Gladstone observed, "...the way to see London is from the top of a 'bus". In India, Bangalore had double deckers for a while before discontinuing. Madras's Metropolitan Transport Corporation (MTC) has a small fleet of double-decker buses mostly in the high-density, longer distance routes. Mumbai has operated double-decker buses since 1937. They are operated by the Brihanmumbai Electric Supply and Transport undertaking. Thiruvananthapuram, Kochi, Kolkata and Hyderabad also have double-decker buses. They are mode led on the London buses. Ashok Leyland Titan double Decker buses are used in all cities. Articulated double Decker buses from Ashok Leyland were used till it was phased out in early 1990s and Volvo B9TL Wrights are now begun operating in Mumbai and Chennai since early 2010 and Enviro400s were also brought into Hyderabad since 2011.

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UNIT 8) VEHICLE STABILITY Steering geometry The steering system on every car is very important and requires regular maintenance to keep it at an optimum standard. The steering rack on all motor vehicles is easily knocked out of alignment by all the speed humps and potholes in the road. When the wheel alignment becomes out of tolerance the tyres will wear unevenly on either edge of the side walls. Noticeable signs of displaced geometry or alignment are:   

Steering wheel is off-set when the vehicle is travelling in a straight line The vehicle may drift/pull to the left or right The front tyres will wear bald or show signs of uneven wear on either edge If any of these faults are present on your vehicle we strongly recommend you have your wheel alignment and steering geometry checked and adjusted if necessary. We advise checking wheel alignment and steering geometry no less than at least once a year though possibly more if there has been noticeable impact are identified. Our highly trained technicians can be of assistance to advise you of the best solution for any steering geometry problems. Curvilinear path Curvilinear motion is defined as motion that occurs when a particle travels along a curved path. The curved path can be in two dimensions (in a plane), or in three dimensions. This type of motion is more complex than rectilinear (straight-line) motion. Motion on a curve => The net force on a car traveling around a curve is the centripetal force, Fc = m v2 / r, directed toward the center of the curve. 127


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=> For a level curve, the centripetal force will be supplied by the friction force between the tires and roadway. => A banked curve can supply the centripetal force by the normal force and the weight without relying on friction. LATERAL STABILITY The stability of a vehicle is that occurs about the longitudinal axis. A vehicle is laterally stable in that when a slight turn takes place, the forces acting on the vehicle tend to restore it.

Vehicle Stability Control (VSC) Helps prevent wheels from slipping sideways when cornering or sudden steering VSC is a system that helps prevent side skids and help stabilize the vehicle while turning on a curve. According to the National Highway Traffic Safety Administration's (NHTSA) report, vehicles equipped with VSC compared to those without can effectively reduce single-vehicle accidents by 35% for automobiles and 67% for Sport Utility Vehicles (SUV). When the vehicle senses a loss of traction or a slip, braking is automatically applied to all 4 individual wheels and engine power is reduced to help secure the safety of the vehicle. For example, if the steering wheel refuses to turn from over-speeding (under-steering), the vehicle will take control to steer toward the inner curve. Also, when the vehicle begins to spin from abrupt steering handling (over-steering), the vehicle will take control to steer toward the outer curve. *VSC is designed to help the driver maintain vehicle control, and it is not a substitute for safe driving Active Safety For Maneuvering

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Anti-Lock Brake System (ABS) Helps prevent brakes from locking Brake Assist Supports unexpected braking in case of emergency Traction Control (TRC) Helps prevent wheel slippage when the vehicle is starting or accelerating on wet or slippery roads Vehicle Stability Control (VSC) Helps prevent wheels from slipping sideways when cornering or sudden steering Vehicle Dynamic Integrated Management (VDIM) Integrated control of "Drive, Turn and Stop" and maintains driving stability Hill-Assist Control (HAC)/Downhill-Assist Control (DAC) Supports drivers on steep hills and descending slopes Tire Pressure Monitoring System (TPMS) Helps prevent accidents caused by decreased tire air pressure For Driving Support

Radar Cruise Control Manages constant distance from the proceeding vehicle Lane Keeping Assist Helps keep drivers within lanes Navigation-Brake Assist Works with the navigation system to provide stop sign information For Visibility

Front and Side View Monitor Helps to verify safety in hard-to-view areas 129


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Multi-Angle Monitor Verifies the vehicle's surroundings Intelligent Adaptive Front-lighting System (AFS) Changes the direction of the headlights based on the cornering angle Night View Detects objects and pedestrians during the nighttime For Pedestrian

Approaching Vehicle Audible System Notifies pedestrians of your vehicle Factors affecting tyre performance

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The factors which influence tyre life: Inflation

Pressure

The science and the technology that has gone into producing even the best quality of tyre will go waste if the tyres are not inflated to the recommended pressure – Pressure comensurating to the load carried. The best performance of tyres can only be achieved when the tyre is inflated to the designated pressure based on the load per tyre. ―Under inflation‖ or ―Over inflation‖ on the tyre tends to impact tyre life, vehicle handling and safety. There are two factors with weight distribution of the vehicle. One is contact patch and other linked to the tyre wear. This result in heat buildup/tyre temperature and thus loss of tyre life, premature tyre removals, increased rolling resistance and fuel consumption. ―Under Inflation‖ is more common than over inflation. Tyre users are not always conscious about maintaining or matching tyre pressure to the loads carried. In pneumatic tyre the ―Air carries the load‖. The best tyre performance and lower tyre CPKM are obtained by maintaining correct tyre inflation pressure. 130

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It is important to remember that the total weight (GVW) carried may not exceed the registered laden weight (RLW) or vehicle passing weight, but one side of the truck or one axle may be severely overloaded due to improper distribution of the load in the pay load platform or loading area. Improper load distribution overloads the tyre(s). This condition combines with high speed , long hauls and load transfers result in tyres wearing fast and premature removal of tyres Loads and Loading practices  It is important to remember that even one trip of the truck; with improper load distribution may cause irreversible damage to the tyres.

Speed  Excessive high speeds results in increased tyre running temperature. As the rubber gets heated up its modulus (stiffness) gets reduced.  Rubber being a good non conductor of heat the residual heat is retained causing increased tyre wear and separation of components. Wheel Alignment  A vehicle is said to be properly align when all the steering and suspension components and set as per the vehicle manufacturer and when the tyre wheel assembly are running straight and true.  Proper alignment is necessary for perfect vehicle control, uniform and even tyre wear and safety.

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Recommended to get the vehicle alignment checked and corrected as per vehicle owner‘s manual as soon as tyre are wearing unevenly or ride handling problems(vibrations, pulling to one side etc).

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Wheel Balancing  A wheel which is not properly balanced may setup vibrations which can affect steering control. Wheels, tyres and tubes are usually checked for balance before leaving factory.  This balance is achieved by positioning weights on the wheel to counterbalance heavy spots on the tyre wheel assembly.  Properly balanced tyres are important for driving comfort and long tyre life.  Tyres should be balanced when they are mounted on the wheels for the first time or when they are removed for repair or periodically as per vehicle manufacturer‘s recommendations.

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Tyre rotation

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Rotation of tyre in a vehicle is recommended for a uniform tyre tread wear on all wheel position to achieve optimum tyre life.  It is preferred to rotate tyres as per vehicle manufacturer‘s recommendation or in case of any uneven tyre wear noticed.  It is suggested to check wheel alignment, wheel balance and suspension before the tyres are rotated. Rotation patterns /pictures to be incorporated. Road Conditions  Vehicle /tyre operating conditions which significantly influence tyre life both in terms of new tyre life and structural durability.  Rough/abrasive road surface  Paved road  Straight road  Broken up roads  Hilly windings roads  Unmade country roads Driving habits  Careful driving habits will ensure optimum tyre life, unavoidable damages besides avoiding serious road accidents. Some of the habits which cause serious damages to tyre and road accidents are:  Over speeding  Speeding over pot holes, stone etc.  Quick starts and sudden stops  Riding over road divider and other obstacles  Sharp turns at high speeds  Hitting the road, curbs, objects etc.  Running on improperly inflated tyres 

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Seasonal Effects  Climatic and whether conditions in our country vary widely from region to region. Dry and extremely hot during summer, extreme cold during winter and rains during monsoon.  These variations in climatic conditions influence tyre life in terms of mileage and structural durability. Do's & Don’ts  Tyre Pressure checks including the spare tyre must be done regularly at least once in two weeks.  Tyre pressure should be checked using an accurate pressure gauge.  Tyre pressure should be checked when tyres are cold.  Under inflation and over inflation will cause rapid tread wear and premature tyre failures.  Tyre pressure should always be maintained as per the vehicle manufacturers recommendations, mentioned at information placard, at door, owner‘s manual.

Weight distribution Weight distribution is very important; not only does it affect the static weight on the different tires; it also affects how the weight shifts in dynamic conditions. The easiest way to judge weight distribution is to determine the car's Center of Gravity (CG). This is a point in space where the mass of the entire car is accounted for. Because of its location, it can be used to simplify the effects of inertia forces. In reality, every little bit of mass is subjected to inertia, but it's much easier to make use of an equivalent condition: assume all the mass of the object is concentrated in its center point, i.e. it's CG. So instead of having to figure out how every part of a 1.5kg car reacts to a certain force, we only have to figure out how a weightless car with a 1.5kg dot in its center(the CG) reacts to it. The latter is much easier: the force only works in the CG, and not in the rest of the car. Of course, this only works when the CG is determined correctly. I think that's a lot of work, and it might not be accurate, so I propose a different method. It's based on the fact that when an object is statically balanced, its CG is right above the point where it's supported. By applying this in three different planes, you can determine an object's CG. Here's an example.

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Here we have an object with a heavy part (dark) and a lighter part (bright) we'd like to determine the CG of. Since the right part is heavier the CG will probably be located somewhere at the right.

We try to balance it on a sharp edge, and this is the position in which the object stays put. So we know the CG is somewhere right above the point where the object is supported.

The red line contains all the points above the point where the object was being supported, so the CG has to be located somewhere on the red line.

We can follow the same procedure, but in a different dimension. Again, we can draw a red line on which the CG is located.

Because this is a 2D example, trying to balance the object 2 times is sufficient to determine it‘s CG (circled in purple). For a car, which has 3 dimensions, you'll need to do it 3 times. It might impose some practical problems, but this is where you'll have to use your imagination. Now that we know where the car's CG is located, we can easily calculate the amount of weight on the tires, and the weight distribution. First, let's have a look at the front-to-rear weight distribution:

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The wheelbase is the distance between the front and rear axle, F is the distance between the CG (green) and the front axle, R is the distance between the CG and the rear axle. Weight on the front axle = weight of the car*(R/WB) Weight on the rear axle = weight of the car*(F/WB) or, in percentages: Front weight percentage = (R/WB)*100% Rear weight percentage = (F/WB)*100% obviously, this will have its effects on handling: more weight on a tire means more grip. So if the CG is located further towards the rear, the car will have a lot of rear traction, which is nice to have if acceleration is important. If the CG is located further towards the front, the car will have a lot of steering, but it might lack rear traction, which increases the risk of spinning out. In some cases, lateral weight distribution is a major concern, especially in so-called LTO (left turn only) cars, which race on oval tracks. It's basically the same deal:

TW is the tread with, the distance between the centers of the tires at the axle, E is the distance between the CG(green) and the centerline of the left side tires, I us the distance between the CG and the centerline of the right side tires. If the front and rear axles aren't equally wide, E and I have to be measured at the CG. Weight on left side = (I/TW)*weight of the car 136


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Weight on right side = (E/TW)*weight of the car Or, in percentages: left side weight percentage = (I/TW)*100% Right side weight percentage = (E/TW)*100% Note that if you need to know the amount of weight on one tire, you need to multiply the weight of the car by 2 factors, one of the lateral balance, and one of the longitudinal balance, for example: Weight on left front tire = Weight of the car*(I/TW)*(R/WB) Weight on right front tire = Weight of the car*(E/TW)*(R/WB) Weight on left rear tire = Weight of the car*(I/TW)*(F/WB) Weight on right rear tire = Weight of the car*(E/TW)*(F/WB) Note that this is only true when the car isn't tweaked; spring preload should be the same on the left and right hand side. Again, having the CG away from the center of the car has consequences for the car's handling: having it toward the left improves the car's ability to turn left, but it might make it very difficult to drive the car in a straight line, especially under acceleration. The height of the CG is also very important: it determines the car's roll characteristics and weight transfer. Sadly enough, that isn't all there is to it; inertia has been left out, rotational inertia to be more precise. Here's an example:

These drawings represent two cars, the first one on the left has all the heavy stuff (blue) located at its ends, far removed from the CG (purple). The second one on the right has all the heavy stuff lined up right in the middle, very close to the CG. Both cars weigh just as heavy, and their CGs are in exactly the same place. So both cars will transfer the same amount of weight while braking or cornering, and their roll angles will also be identical. Yet they won't handle the same, because their rotational moment of inertia is different. The first car will react slowly, turn in a little sluggishly and it will generally be more reluctant to change direction. Some might say it is slow, others might find it very stable, and it‘s the same thing. The second car will feel like the 137


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opposite: it will change direction very quickly, and it will feel very nimble, and thus also unstable. So, rotational moment of inertia doesn't change how far the car's chassis moves, it changes how fast it does so. It's kind of like swinging a baseball bat with a big, heavy tip: you'll need a lot of effort to get it going, and once you get it going, there's not much you can do to alter its course. The rotational moment of inertia can be calculated too: the rotational moment of inertia of a body around an axis is the sum of all the elementary masses of the body multiplied by their distance to that axis squared. For simple-looking bodies like cylinders, cubes and cones and such, you can do this by hand, but for real-life applications you'll need a sophisticated CAD program. Note that it's also important around which axis you're calculating the rotational moment of inertia. Consider the following example:

These drawings represent identical cars, except for the fact that they have their weight distributed differently: the first one has its heavy components (blue) lined up along its lateral axis (purple) and the second one has its heavy stuff lined up along its longitudinal axis. Consider the first car. If we calculate the rotational moment of inertia around its lateral axis, we have to multiply all of the masses with their distance to the axis squared. In this case, we have to multiply most of the mass with a very small distance squared, resulting in a very small value. On the other hand, if we calculate its rotational moment of inertia around its longitudinal axis (not drawn), we have to multiply most of the mass with a very large distance squared, resulting in a large value. So, the first car has a very large moment of inertia around its longitudinal axis, and a very small one around its lateral axis. In other words, this car will react very slowly while cornering; it will move from side to side (roll) very slowly. But, it will move from front to rear (pitch) very easily, this might be beneficial for quick braking, but it will make the car bounce back and forth in bumps, making it very unstable.

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For the second car, the opposite is true: it has a large value for its rotational moment of inertia around its lateral axis (not drawn) and a very small one around the longitudinal axis. This means that the car will roll quickly, and be very responsive in turns, but it will be very stable front to rear. This helps stabilize the car in bumps while maintaining good cornering abilities. Maybe now you can understand the hype about mid-mounted motors in fullscale cars: the motor is by far the heaviest item, so by positioning it centrally, the car's rotational moment of inertia is reduced, making for a more nimble handling car.

Most modern vehicles‘ engines are located to the front of the driver. However, some manufacturers place locate the engine at some location point behind the driver. Due to the weight of the engine, its location can substantially impact a vehicle‘s handling, behavior, and response characteristics. The goal of this article is to discuss the dynamic differences among front-, mid-, and rear-engine configurations. Have you ever lifted the hood of a modern passenger car, only to find no motor? For most drivers, this has not occurred, as most vehicles‘ engines are located up front. But if you drive a mid- or rear-engine vehicle, you would be accustomed to having only storage space up front under the hood. The goal of this article is to discuss the different engine locations and their impact on vehicle dynamics.

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Front-Engine Vehicles By far the most common engine location is at the front of the vehicle, ahead of the driver and the front axle line. While the earliest automobiles used a variety of engine locations, front-engine vehicles quickly became the norm for financial and engineering reasons. For example, most front-engine vehicles feature relatively easy access to the motor for maintenance and repair. Positioning the engine ahead of the driver also impacts space considerations such as permitting permits a full-size interior. In addition, most front-engine vehicles feature large cabins, usually with seating for four or more occupants, including relatively spacious rear seating areas. Interior sound levels are also reduced because the engine is not directly adjacent to the cabin. The static weight distribution of front-engine vehicles (the weight of the front and rear of the automobile expressed in percentages) is generally favorable with between 50-66% of the vehicle‘s weight over the front wheels (Bondurant ‗ Blakemore, 1998). Most front-engine vehicles feature relatively easy access to the motor for maintenance and repair. Placing the engine up front also has some disadvantages. First, braking ability is somewhat diminished. Diminished braking occurs because weight transfers forward under braking (Karasa, 2001), leaving relatively little weight remaining over the rear wheels during braking and thus, limiting the ability of the rear tires to contribute the braking task. Second, accelerative ability is limited somewhat by the relative lack of static weight over the rear tires when, the weight of the vehicle shifts rearward upon acceleration (Scotti, 1995). Despite its relative drawbacks, the front-engine layout remains the most popular.

Mid-Engine Vehicles In a mid-engine configuration the engine is located directly behind the cabin just ahead of the rear axle line. Essentially, the engine is located in the rear seat area. A rare configuration, the mid-engine vehicle is usually associated with high performance automobiles for several reasons. First, the static weight distribution tends to be close to the optimal 50/50 ratio, with the bias being slightly rearward, resulting in superior balance and handling 140


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characteristics (Bondurant ‗ Blakemore, 1998). Second, the vehicle‘s mass (center of gravity) is the static weight distribution of front-engine vehicles (the weight of the front and rear of the automobile expressed in percentages) is generally favorable with between 50-66% of the vehicle‘s weight over the front wheels (Bondurant ‗ Blakemore, 1998). Most frontengine vehicles feature relatively easy access to the motor for maintenance and repair. Placing the engine up front also has some disadvantages. First, braking ability is somewhat diminished. Diminished braking occurs because weight transfers forward under braking (Karasa, 2001), leaving relatively little weight remaining over the rear wheels during braking and thus, limiting the ability of the rear tires to contribute the braking task. Second, accelerative ability is limited somewhat by the relative lack of static weight over the rear tires when, the weight of the vehicle shifts rearward upon acceleration. Despite its relative drawbacks, the front-engine layout remains the most popular.

Rear-Engine Vehicles In rear-engine vehicles, the motor is located in the rearmost portion, behind the rear axle line. Essentially, the engine is located in the trunk. Also a rare configuration, rear-engine automobiles tend to demonstrate exceptional braking ability due to a greater amount of weight from the engine remaining over the rear tires during braking. Thus, all four tires are heavily involved during braking instead of just the front tires. Acceleration is also enhanced, as the rearward transfer of weight and the engine weight combine to put maximum downward force on the rear tires (the tires responsible for acceleration in this configuration) resulting in a larger rear tire contact patch that enhances accelerative traction (Bentley, 1998). While it may appear that rear-engine vehicles are the answer to all automotive needs, they do have drawbacks. First, the cabin generally has less room for rear passengers than does a front-engine vehicle. Some rearengine cars do feature rear seats, but many do not offer enough room to carry rear passengers. Even in vehicles that do feature rear seats, the seats are often so small that the only passengers able to sit comfortably in them are children. 141


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Perhaps even more disadvantageous is the rear-engine vehicle‘s tendency to oversteer due to greater weight resident in the rear of the vehicle that results in greater momentum. Recalls that oversteer (rear wheel) skids occur when the rear tires lose traction before the front tires, resulting in the rear of the car sliding out sideways or "fishtailing." (How to Drive, 2004). As oversteer skids are less easily corrected than understeer (front wheel) skids, this can be a problem for drivers not experienced and skilled in the driving dynamics of rear-engine cars" (Rich, 1998). To help visualize this situation, imagine that you are playing a friendly game of darts. Instead of throwing your next dart normally, with the nose-heavy pointed end leading, you turn the dart around, throwing it fin-first toward the dartboard. Which end of the dart will eventually contact the dartboard? Indeed, the heavier end will spin in mid air during flight and contact the dartboard first. Under conditions of low traction or excessive speed, it‘s the same with rear-engine vehicles; the rear of the vehicle will always want to "swap ends" with the front. Front-engine vehicles can be either front or rear wheel drive, while all midand rear-engine vehicles are rear wheel drive. Table 1 displays a summary of the relative advantages and disadvantages of each engine location. In dry conditions under normal driving conditions, the location of the engine does not make much of a difference in terms of driving dynamics. Aside from the mid-engine vehicle‘s tendency to yield higher interior noise levels, most drivers will not detect a difference in the way these different vehicles respond to driver inputs. However, as the driving turns more spirited or involved emergency situations requiring abrupt driver inputs, these differences can surface, sometimes to the negative surprise of the driver. Generally, mid- and rear-engine vehicles will benefit the driver by offering shorter potential stopping distances and will disadvantage the driver to the degree that these layouts are more ends" with the front. Front-engine vehicles can be either front or rear wheel drive, while all midand rear-engine vehicles are rear wheel drive. Table 1 displays a summary of the relative advantages and disadvantages of each engine location. In dry conditions under normal driving conditions, the location of the engine does not make much of a difference in terms of driving dynamics. Aside from the mid-engine vehicle‘s tendency to yield higher interior noise levels, most 142


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drivers will not detect a difference in the way these different vehicles respond to driver inputs. However, as the driving turns more spirited or involved emergency situations requiring abrupt driver inputs, these differences can surface, sometimes to the negative surprise of the driver. Generally, mid- and rear-engine vehicles will benefit the driver by offering shorter potential stopping distances and will disadvantage the driver to the degree that these layouts are more likely to oversteer than their frontengine counterparts. As with front-, rear- and all-wheel-drive, modern traction maintenance systems tend to equalize the dynamic differences among front-, mid- and rear-engine vehicles (Wilson, 2005). Known generally as "dynamic stability control" systems, these computerized anti-skid systems help prevent negative events resulting from driving beyond these vehicles‘ limits. These systems monitor the vehicle‘s accelerative forces and very quickly adjust individual wheel speeds to reduce the chance of the driving losing control. Manufacturers currently offer few mid- and rear-engine vehicles. The frontengine configuration remains the most popular layout. However, driving instructors may find themselves in a position to field questions about the difference among engine locations. It is hoped that this article contributes to preparing instructors to provide accurate information on this topic.

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Vehicle Body Engineering by M A Qadeer Siddiqui

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