Panther Racing 2009 Florida Tech FSAE Team Preliminary Design Report October 22, 2008
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Table of Contents 1.1 Introduction ............................................................................................................................... 9 1.1.1 Purpose................................................................................................................................... 9 1.1.2 Goals .................................................................................................................................... 10 1.1.3 Background .......................................................................................................................... 11 1.1.4 Team Organization............................................................................................................... 11 1.1.5 Scheduling............................................................................................................................ 12 1.1.5.1 Milestones and Deadlines ................................................................................................. 12 2.1 Chassis .................................................................................................................................... 13 2.1.1 Introduction and Purpose ..................................................................................................... 13 2.1.2 Goals .................................................................................................................................... 13 2.1.3 Background .......................................................................................................................... 13 2.1.4 Design Objectives ................................................................................................................ 14 2.2 Formula SAE Rules and Regulations ..................................................................................... 14 2.3 Chassis Design and Analysis .................................................................................................. 17 2.3.1 Chassis Design Introduction ................................................................................................ 17 2.3.2 Design Analysis ................................................................................................................... 18 2.4 Budget ..................................................................................................................................... 20 2.5 Scheduling............................................................................................................................... 20 2.5.1 Gantt Chart ........................................................................................................................... 20 2.5.2 Milestones and Deadlines .................................................................................................... 20 2.6 Conclusions ............................................................................................................................. 21 3.1 Suspension .............................................................................................................................. 21 3.1.1 Introduction and Purpose ..................................................................................................... 21 3.1.2 Goals .................................................................................................................................... 21 3.1.3 Background .......................................................................................................................... 22 3.2 Design Objectives ................................................................................................................... 22 3.2.1 Suspension Definitions ........................................................................................................ 23 Shock absorbers, and travel ................................................................................................... 23 2
Ground Clearance .................................................................................................................. 23 Wheelbase and Track Width.................................................................................................. 23 Kingpin Inclination and Scrub Radius................................................................................... 23 Camber................................................................................................................................... 24 Caster ..................................................................................................................................... 25 Toe ......................................................................................................................................... 26 3.3 Design Analysis ...................................................................................................................... 27 3.3.1 Braking Analysis .................................................................................................................. 29 3.3.1.1 Braking Calculations......................................................................................................... 31 3.4 Detailed Drawings .................................................................................................................. 34 3.5 Budget ..................................................................................................................................... 35 3.6 Scheduling............................................................................................................................... 35 3.6.1 Gantt Chart ........................................................................................................................... 35 3.7 Conclusions ............................................................................................................................. 36 4.1 Drivetrain ................................................................................................................................ 36 4.1.1 Introduction .......................................................................................................................... 36 4.1.2 Purpose................................................................................................................................. 36 4.1.3 Goals .................................................................................................................................... 36 4.1.4 Background .......................................................................................................................... 37 4.2 Design Objectives ................................................................................................................... 37 4.3 Design and Analysis ............................................................................................................... 38 4.3.1 Drivetrain Analysis .............................................................................................................. 38 4.3.2 Engine Choice ...................................................................................................................... 40 4.3.3 Transmission Analysis ......................................................................................................... 42 4.4 Detailed Drawings .................................................................................................................. 45 4.5 Budget ..................................................................................................................................... 46 4.6 Scheduling............................................................................................................................... 47 4.6.1 Gantt Chart ........................................................................................................................... 47 4.6.2 Milestones and Deadlines .................................................................................................... 47 4.7 Conclusions ............................................................................................................................. 48 5.1 Driver Interface ....................................................................................................................... 49 3
5.1.1 Introduction and Purpose ..................................................................................................... 49 5.1.2 Goals .................................................................................................................................... 49 5.2 Design Objectives ................................................................................................................... 49 5.3 Driver Interface Design and Analysis ..................................................................................... 49 5.3.1 Accelerator and Clutch Pedals ............................................................................................. 49 5.3.1.1 Engineering Specifications ............................................................................................... 49 5.3.1.2 Design History .................................................................................................................. 50 5.3.1.3 Engineering Analysis ........................................................................................................ 50 5.3.1.4 Material Study ................................................................................................................... 51 5.3.2 Brake Pedal .......................................................................................................................... 51 5.3.2.1 Engineering Specifications ............................................................................................... 51 5.3.2.2 Design History .................................................................................................................. 51 5.3.2.3 Material Study ................................................................................................................... 51 5.3.3 Steering Wheel ..................................................................................................................... 52 5.3.3.1 Engineering Specifications ............................................................................................... 52 5.3.3.2 Design History .................................................................................................................. 52 5.3.3.3 Material Study ................................................................................................................... 53 5.3.4 Steering Rack ....................................................................................................................... 53 5.3.4.1Engineering Specifications ................................................................................................ 53 5.3.4.2 Design History .................................................................................................................. 54 5.3.5 Driver’s Seat ........................................................................................................................ 54 5.3.5.1 Engineering Specifications ............................................................................................... 54 5.3.5.2 Design History .................................................................................................................. 54 5.3.5.3 Material Study ................................................................................................................... 54 5.3.6 Instrumentation .................................................................................................................... 55 5.3.6.1 Engineering Specifications ............................................................................................... 55 5.3.6.2 Design History .................................................................................................................. 55 5.3.7 Safety Equipment ................................................................................................................. 56 5.3.7.1 Engineering Specifications ............................................................................................... 56 5.3.7.2 Material Study ................................................................................................................... 57 5.4 Engineering Drawings ............................................................................................................ 57 4
5.5 Budget ..................................................................................................................................... 57 5.6 Gantt Chart .............................................................................................................................. 59 5.7 Conclusion .............................................................................................................................. 59 6.1 References ............................................................................................................................... 60
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List of Figures Figure 1 - Formula Team Chain of Command.............................................................................. 12 Figure 2 – Helmet Clearance [1] .................................................................................................. 16 Figure 3 - Solid Works Rendering of Chassis Regulations .......................................................... 17 Figure 4– First Chassis Design Model .......................................................................................... 19 Figure 5– Redesigned Chassis ...................................................................................................... 19 Figure 6– Chassis Sub-Team Gantt Chart .................................................................................... 20 Figure 7 - Diagram of Kingpin Inclination and Scrub Radius [4] ................................................ 24 Figure 8- Camber [5] .................................................................................................................... 25 Figure 9- Caster [6] ....................................................................................................................... 26 Figure 10- Toe Angles [7]............................................................................................................. 26 Figure 11- Example of Double Wishbone with Pull rods [8] ....................................................... 27 Figure 12- Plan View of Arning Four-Link [9] ............................................................................ 28 Figure 13- Wilwood Brake Caliper from Side Mount Car ........................................................... 29 Figure 14– Upright from Side Mount Car .................................................................................... 29 Figure 15– Center Locking Wheel off of 2005 Side Mount Car .................................................. 30 Figure 16– Front Suspension Drawing ......................................................................................... 34 Figure 17– Gantt Chart Suspension Sub-Team ............................................................................ 35 Figure 18— Cutaway of differential (Torsen T-1) [11]................................................................ 39 Figure 19- Drive Train Prototype Florida Tech 2003 Car ............................................................ 40 Figure 20–(a)Pro E model of CRF450R Engine Model ............................................................... 40 Figure 21– Actual CRF450R[12].................................................................................................. 41 Figure 22- Dyno chart for the CRF450R ...................................................................................... 44 Figure 23- Detailed Drawing of the Torsen T-1 Differential [12] ................................................ 45 Figure 24– Gantt Chart for Drivetrain Sub-Team......................................................................... 47 Figure 25. Side-mount car pedal setup ......................................................................................... 50 Figure 26- Wilwood Dual Cylinder brake assembly [2] ............................................................... 52 Figure 27- Steering wheel of the side-mount ................................................................................ 53 Figure 28- Steering Rack of the side-mount ................................................................................. 54 Figure 29- Tillet T8 Racing Seat [1] ............................................................................................. 55 Figure 30- Summit Racing gauges................................................................................................ 56 Figure 31- Wilwood Pedal [2] ...................................................................................................... 57 Figure 32– Gantt Chart Driver Interface Sub-Team ..................................................................... 59
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List of Tables Table 1– Competition Event’s Points Breakdown [1] .................................................................. 10 Table 2– Formula Team Deadlines ............................................................................................... 12 Table 3– Minimum Material Requirements [1] ............................................................................ 16 Table 4– Material Selection Chart for Chassis Construction [3] .................................................. 18 Table 5– Chassis Sub-Team Budget ............................................................................................. 20 Table 6 - Front Suspension Geometry .......................................................................................... 28 Table 7– Initial Suspension Sub-Team Budget ............................................................................ 35 Table 8- Differential Specification [2] .......................................................................................... 39 Table 9- Engine Specifications ..................................................................................................... 41 Table 10- Graph above shows regular and custom setup for the gear box of the car[13] ............ 43 Table 11 - Drive Train Budget ...................................................................................................... 46 Table 12 Engine Budget................................................................................................................ 46 Table 13- Parts Availabilities or Prices. ....................................................................................... 59
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Team Members: Kyle Meier Keith Reihl Jeff Grubesich Mert Candarli Jacob Allenbaugh Earle Jackson Sebastien Griveau Joachim Agou Joel Zahlan Talal Almoyaed Guido Carelli
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1.1 Introduction Florida Tech Motorsport‟s history of racing teams continues this year with another Formula SAE series team. This year the team will be going to the competition held in Michigan International Speedway where the team will continue the traditions of the old racing teams and plans to place well at the competition. The design for this year‟s car incorporates revisions and new ideas that will improve the handling and drivability. A new engine will be used instead of the standard four cylinder 600cc motorcycle motor that has been used for all of the other formula cars, but parts from previous cars will be taken to keep costs down and save time. We look to make this year‟s design superior to the previous cars. The team is comprised of 11 students all studying mechanical engineering. All design, analysis and manufacturing will be done by the students. We continue to analyze and research to find the best solutions to the many problems this design encounters.
1.1.1 Purpose The Formula SAE Series competitions challenge teams of university undergraduate and graduate students to conceive, design, fabricate and compete with small, formula style, autocross racing cars. To give teams the maximum design flexibility and the freedom to express their creativity and imaginations there are very few restrictions on the overall vehicle design. Teams typically spend eight to twelve months designing, building, testing and preparing their vehicles before a competition. The competitions themselves give teams the chance to demonstrate and prove both their creativity and their engineering skills in comparison to teams from other universities around the world. The competition is based on two types of events, static and dynamic. The static events provide the judges with insight into the design process that went into building the vehicle while the dynamic events allow the vehicle to show how well it can handle, accelerate and brake and its fuel economy. The static events consist of a presentation, engineering design event, and a cost analysis and the dynamic events consist of acceleration, skid-pad, autocross, fuel economy and endurance. The point‟s breakdown can be seen in table 1 below.
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Static Events:
Dynamic Events:
Event
Points
Presentation
75
Engineering Design
150
Cost Analysis
100
Acceleration
75
Skid-Pad
50
Autocross
150
Fuel Economy
100
Endurance
300
Total Points
1,000
Table 1– Competition Event’s Points Breakdown [1]
It‟s obvious that the most points come from the endurance event, so a design that can withstand the dynamic abuse of a race car will prevail. Another interesting area of the competition is the fuel economy event which has had an impact on some decisions that the team has made. Students participating in the Formula series learn how to implement the ideas and theories of the classroom into real life applications. The design of the car includes static and dynamic analyses, driver ergonomics, cost efficiency, teamwork, and learning. The intricate design process of the car must be done with precision and accuracy.
1.1.2 Goals The goals of our Formula team are:
Design and build an open wheel, formula style, race car
High performance in acceleration, braking and cornering
Attend competition at Michigan International Speedway
Learn and take part in the engineering design process
Have a well tested car for competition
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1.1.3 Background The Formula SAE series began as a mini-Indy style race car competition in 1979 and was held at the University of Houston. Dr. Kurt M. Marshek conceived the competition by reading an article out of a Popular Mechanics magazine. The series gained interest by universities across the United States and soon by international universities. In 1980 three students at the University of Texas decided to start another Indy style event with new rules but with minimal restrictions. The University hosted the competitions up until 1984, and after that new concepts were added by Dr. Robert Woods of the University of Texas at Arlington. The concept of building an all out Indy race car was changed to one that mimicked the Mini Baja competition. The teams were to design a race car based on an imaginary engineering firm that wanted to produce and market formula style race cars to non-professional autocross racers. This tradition continued on and after the 1992 competition Ford Motor Co., Chrysler Corp., and General Motors formed an association to run what is now known as Formula SAE. Florida Tech‟s involvement in the Formula SAE Series has proven a success in building and racing formula style cars. Florida Tech‟s highest placement in the competition was from the 2004 formula car. The car placed 43rd out of 134 teams in competition which overcame the 80th place finish done by the 2003 formula car. Our team this year hopes to place even higher this year with the new motor selection and suspension design.
1.1.4 Team Organization Four sub-teams comprise our formula team which consist of suspension, chassis, drive train, and driver interface teams. The 11 members making up the team were divided into a sub-team they were interested in. Displayed below is the formula team chain of command.
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Figure 1 - Formula Team Chain of Command
1.1.5 Scheduling 1.1.5.1 Milestones and Deadlines The team reached a huge milestone on October 6th, 2008 when we were able to register for the Michigan International Speedway competition held from May 13th to May 16th, 2009. This was the first major milestone the team has had. Deadlines associated with the team consist of the following:
Action
Deadline
Safety Plan Human Safety Analysis Failure Modes and Effects Analysis Formula SAE Structural Equivalency Form Impact Attenuator Data Design Report & Design Spec Sheet Cost Report Fuel Type Order Senior Design Final Design Report Student Design Showcase
11/7/2008 2/6/2009
2/1/2009 3/1/2009 3/2/2009 4/1/2009 4/1/2009
12/3/2008 4/3/2009
Table 2– Formula Team Deadlines
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2.1 Chassis 2.1.1 Introduction and Purpose The chassis houses all the sub-systems and components of the car, and is one of the most important aspects of the entire vehicle. The chassis must be designed to keep the driver safe if any collisions occur and provide a stiff backbone for all of the components of the car to operate correctly. An optimal chassis must be lightweight and rigid that allows for very little deflection under static and dynamic conditions. If any part of the chassis fails, it would be detrimental to the entire vehicle, so proper consideration must be done in order to not have any failures.
2.1.2 Goals The chassis sub-team has set design goals in order to produce the most optimal chassis for our vehicle. The goals include:
Abiding by all Formula SAE rules and regulations
Obtaining a torsional rigidity greater than 2500 lbf/degree
Fit the 95th percentile male driver
Allow all components of the vehicle to fit properly and securely
Have a weight of around 50 lbs.
Optimization using finite element analysis software, ANSYS
2.1.3 Background Spaceframe chassis design has been incorporated into racing vehicles since the dawn of racing. The design is based on tubular or rectangular bars, triangulated to provide stiffness against the static and dynamic loads associated with a race car. The simplicity associated with a spaceframe allows for great design innovations and ease of maintenance. The chassis must incorporate all the systems that allow the car to drive while keeping the driver safe and comfortable. Safety is of the utmost concern when designing the chassis because if a 13
collision does occur, one must be sure that the driver of the vehicle will not be injured; therefore, the cockpit design is crucial to the development of the chassis. While designing the chassis for all its optimizations and safety concerns, the engineer must also take into consideration the rules and regulations set forth by the Formula SAE competition. Proper reading of the rules ensures that a team will not be disqualified when arriving to the competition.
2.1.4 Design Objectives The main design objectives for the chassis are:
Research fundamentals behind designing a spaceframe that will see forces associated with a race car
Research chassis materials that can withstand the high performance ratings of a formula style race car
Design a chassis that will be able to withstand the loads from static and dynamic forces using solid modeling software
Perform static and dynamic load analysis using finite element analysis software
Optimize the chassis by lowering high stress concentration areas using better triangulation of the frame members and gusseting
Finalize a chassis design that meets all requirements and regulations and begin testing of the vehicle once all the systems have been implemented into the vehicle
2.2 Formula SAE Rules and Regulations The governing body presiding over the competition is Formula SAE, and they have defined an intensive list of all the rules and regulations for the competition. The team must adhere to all rules presented by Formula SAE in order to compete. There are some significant rules that need to be discussed in order to show how the chassis sub-team designed the chassis, and all other rules can be seen in „PART B – TECHNICAL REQUIRMENTS.‟ These rules include, but are not limited to:
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„2.1 Vehicle Configuration – The vehicle must be open-wheeled and open cockpit (a formula style body) with four (4) wheels that are not in a straight line‟ [1]
The car‟s wheelbase must be a minimum of 60 inches
„3.1 General Requirements – Among other requirements, the vehicle‟s structure must include two rolls hoops that are braced, a front bulkhead with support system and Impact Attenuator, and side impact structures.‟ [1]
„Primary Structure – The Primary Structure is comprised of the following Frame components: o 1)Main Hoop, 2)Front Hoop, 3)Roll Hoop Braces, 4)Side Impact Structure, 5)Front Bulkhead, 6)Front Bulkhead Support System and 7)all Frame Members, guides and supports that transfer load from the Driver‟s Restraint System into items 1 through 6.‟ [1]
The minimum material requirements states that the primary structure of the car must be constructed of either round, mild, or alloy steel tubing with a minimum of 0.1% carbon
Figure 2 outlines how the driver must fit in the car in relation to the main roll hoop and
Table 3 provides minimum material requirements for various parts of the vehicle
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Figure 2 – Helmet Clearance [1]
ITEM or APPLICATION Main & Front Hoops, Shoulder Harness Mounting Bar Side Impact Structure, Front Bulkhead, Roll Hoop Bracing, Driver‟s Restraint Harness Attachment Front Bulkhead Support
OUTSIDE DIAMETER X WALL THICKNESS 1.0 inch (25.4mm) x 0.095 inch (2.4mm) or 25.0mm x 2.50 mm metric 1.0 inch (25.4mm) x 0.065 inch (1.65mm) or 25.0mm x 1.75 mm metric or 25.4mm x 1.60mm metric 1.0 inch (25.4mm) x 0.049 inch (1.25mm) or 25.0mm x 2.50 mm metric or 26.0mm x 1.2mm metric
Table 3– Minimum Material Requirements [1]
The rest of the rules can be viewed on the Formula SAE website where there is more information on the constraints for the vehicle. These were the more important rules that needed to be highlighted.
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2.3 Chassis Design and Analysis 2.3.1 Chassis Design Introduction Chassis design began with the regulations set forth by the Formula SAE rules committee, and from those given dimensions a basic shape of the chassis was formed as seen in figure 3.
Figure 3 - Solid Works Rendering of Chassis Regulations
The cockpit, 95th percentile male, and leg tunnel dimensions were all given information in the 2009 rules, and were modeled in Solid Works to have a visual of what to expect this year‟s chassis to look like. Among these specifications set forth by Formula SAE, we need to account for the incorporation of a motor, drive train, suspension components, and various other subsystems. Stress calculations need to be looked at to ensure optimal operation of all components in the vehicle and ensure failure does not occur. The American Society for Nondestructive [2] testing has set a standard for the factor of safety for these cars at 3. With this key factor in mind, it allows the team to narrow down materials that can be considered for the construction of the chassis. Table 2 defines a material selection chart for determining the material for chassis construction with properties from Matweb.com [3].
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Material Candidates
AISI 4130 Steel T6-6061 Aluminum AISI 1020 Steel
UTS
Design Requirements Yield Strength Absolute Relative Value Value 63.1 ksi 1.00
Absolute Value 97.2 ksi
Relative Value 1.00
45 ksi
0.46
40 ksi
0.63
55.1 ksi
0.57
29.7 ksi
0.47
Density Absolute Relative Value Value 0.284 0.34 lb/in3 0.0975 1.00 lb/in3 0.284 0.34 lb/in3
Overall Rating 0.99 0.54 0.53
Table 4– Material Selection Chart for Chassis Construction [3]
AISI 4130 chromoly steel outranks both T6 aluminum and 1020 alloy steel drastically. This choice of material was used in all of the previous formula cars designed by Florida Tech teams, so its strength and durability has been tried and tested. 4130 steel comes in square and round tubes, and we have designed the chassis around using round tubes due to the increase in torsional stiffness seen by the constant moment of inertia around a central axis which is defined by the following equation. – Moment of Inertia of a circle with constant cross sectional area Utilizing the factor of safety of 3 and the Ultimate Tensile Strength of 4130 steel of 97.2 ksi, we obtained a new UTS of 32.4 ksi, and for the Yield Strength we come to 21 ksi. These values will be used to determine whether or not the chassis will fail at the loads seen during static and dynamic loadings. If the chassis sees a stress greater than the Yield Strength, the chassis will plastically deform and the structure will be compromised, but if it exceeds the UTS, then the structure will fail. Neither of these situations should be seen when driving the car, so proper gusseting and triangulation will be placed into the design to ensure these stresses will never be seen.
2.3.2 Design Analysis Designs of previous cars were looked upon for ideas about how to conceptualize a new chassis and cars from other competing teams were looked at for more ideas. Preliminary chassis designs took shape in Solid Works and improvements were made on these designs to incorporate the various systems of the car. The first design, as seen in figure 3, shows a model in Solid Works with members that conform to all the rules and regulations. The chassis uses basic geometry to satisfy regulations and triangulation was used to provide stiffness to the overall design.
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Figure 4– First Chassis Design Model
This model allowed us to see what challenges would come about. A rendered model of the engine was placed into the conceptual chassis design, and we soon found out that we needed to resize and move certain members that interfered with the engine mounting. A redesigned chassis with better placement of frame members can be seen in figure 5 below.
Figure 5– Redesigned Chassis
This new chassis design allows better fitment for the engine and suspension geometry has been updated to incorporate a new suspension design.
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2.4 Budget
Part 4130 Steel Tubing 1'' OD x 0.095'' Wall 1'' OD x 0.065'' Wall 1'' OD x 0.049'' Wall Tabs 11 GA HRPO Radius Tab
Part Number/Code 4130 - ALLOY TUBE ROUND 4130 - ALLOY TUBE ROUND 4130 - ALLOY TUBE ROUND 02-105
Unit Price
Quantity Price
Company
$7.89
15
$118.35 olinemetals.com
$6.02
70
$421.40 olinemetals.com
$5.80
15
$87.00 olinemetals.com
$1.75
26
$45.50 tabzone.com
TOTAL
$672.25 Table 5– Chassis Sub-Team Budget
2.5 Scheduling 2.5.1 Gantt Chart
Figure 6– Chassis Sub-Team Gantt Chart
2.5.2 Milestones and Deadlines Milestones already seen by the chassis sub-team include modeling a preliminary design in Solid Works and working with this model to optimize it for all of the sub-systems. The sub-team plans on having a chassis mock up built with conduit by the middle of November as seen on the Gantt
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chart. After a successful building of a mock up chassis, the real chassis fabrication can begin. Deadlines associated with the chassis sub-team can be viewed in the Gantt chart above.
2.6 Conclusions A properly designed chassis will prove to make the entire project run more smoothly and fewer headaches will be felt by the team. Close attention to detail in the design will yield promising fitment and results in the future of this team. More analysis needs to be done on the chassis itself, and once that is complete or almost complete more analysis on the attachment points for the engine, drivetrain and suspension components.
3.1 Suspension 3.1.1 Introduction and Purpose Although the car we hope to build is not an off-road vehicle and does not have the suspension requirements of such, suspension is still a major aspect of the efficiency of the vehicle. The suspension system serves a dual purpose – contributing to the car's handling and braking for good active safety and driving performance, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations. Although these goals are generally at odds and tuning must find the right compromise, driver comfort is not a big priority in the flat track we must run, so our car‟s tuning will be focused on performance. With the technology available today, an ideal suspension system for a track car will balance out the forces experienced while turning from one side to the other and while braking from the front to the rear, however we aim to keep the design simple and cost efficient so we will use independent wheel system. Our suspension system will focus on providing maximum traction at all times and to control the sway of the car during steering and braking.
3.1.2 Goals The goals of the suspension sub-team are the following: •
Design and create a suspension system that will meet all the SAE specifications and design objectives
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•
To maximize traction so as to have maximum deliverance of power
•
To cancel out the uneven weight distribution experienced during turns and braking
•
Maximize vehicle performance with optimal use of suspension
•
Perform well in competition
3.1.3 Background SAE requires that we are to assume that we work for a design firm that is designing, fabricating, testing and demonstrating a prototype vehicle for the non-professional, weekend, competition racer market [4]. The vehicle should have a very high performance in terms of acceleration, braking, and handling and be sufficiently durable to be successful at the events described in the formula SAE rules and held at the Formula SAE competition [5].
3.2 Design Objectives Our primary objectives will be to fulfill the design requirements instituted by the SAE rules. According to the SAE 2009 rules we must build a car with a fully operational suspension system with shock absorbers, front and rear, with usable wheel travel of at least 50.8mm (2inches), 25.4mm (1inch) jounce and 25.4mm (1inch) rebound, with driver seated. The judges reserve the right to disqualify cars which do not represent a serious attempt at an operational suspension system or which demonstrate handling inappropriate for an autocross circuit [6]. Rules also state that all suspension mounting points must be visible at Technical Inspection, either by direct view or by removing any covers. Finally, the ground clearance must be sufficient to prevent any portion of the car (other than tires) from touching the ground during track events, and with the driver aboard there must be a minimum of 25.4mm (1inch) of static ground clearance under the complete car at all times [7]. The car will be traveling on even terrain therefore when analyzing suspension we will only be dealing with two major forces, cornering and braking. Lateral force is the forces exerted on the suspension arms as the vehicle turns and the weight of the vehicle shifts towards one side. The braking force is the force on the suspension arm created when the weight distribution of the car shifts to the forward steering knuckle as the car breaks. To calculate forces due to cornering, we must understand the forces created as the car pushes against the asphalt, thus friction comes into play. In extreme turns we can assume that the full weight of the vehicle will shift to one side of the car or even to one tire thus we must prepare 22
the a-arm to withstand such force. When the full weight of the car is established we can run calculations to find the normal force experience if the entire weight of the car were to shift to one side or even one wheel. For the braking forces we will perform similar calculations. As the vehicle brakes, the brake caliper will force the brake pads into the rotor so as to stop its motion. Once the rotor is locked the breaking force will be created by the friction as the weight of the car travels forward. The braking force will then create a moment that will translate into the suspension arm through the steering knuckle. Thus our design will have to sustain this moment.
3.2.1 Suspension Definitions Shock absorbers, and travel Shock absorbers and dampers are important elements of suspension and are the key element to supporting and balancing the forces that the arm will be suffering. We will use adjustable dampers so as to be able to control our jounce and bounce and also tune the suspension for greater efficiency. Also, adjustable shocks will allow us to fine tune the suspension to the different weight of different drivers. Shocks will be connected to the top A-arm via a pull rod for the front suspension, thus mounting will be considered when analyzing stresses. The rear suspension will use the more commonplace pushrod style where the link connects to the lower A-arm. The connection to the A-arm will also determine the travel of the wheel assembly. Ground Clearance The lower suspension arm will also determine our ground clearance. SAE 2009 rules specify a particular ground clearance as stated earlier. The tuning of shocks and the design of the lower arm will all have to fit in order to achieve this clearance. Wheelbase and Track Width The minimum wheel base of the car is 60‖. The track widths may be different, but the smaller track width cannot be less than 75% of the larger track width. The track width is measured from the centerlines of the wheels. The chosen track width for the front of the car is 48‖. This will provide a stability, but it’s not so wide that it will hinder or cornering and maneuverability. The wheelbase is set at the competition minimum of 60‖. Kingpin Inclination and Scrub Radius The first parameter that had to be determined besides track width was kingpin inclination. This is the angle between vertical and the axis running through the upper and lower ball joints (see figure 7). The kingpin inclination affects steering performance and return ability. This is 23
interrelated with the scrub radius and the spindle length, which were minimized for this design. The spindle length is the distance from the kingpin axis to the centerline of the wheel at the wheel axis. The scrub radius is the distance from the kingpin axis to the center of the wheel at the ground. By minimizing the spindle length and scrub radius, the jacking effect when the wheels are steered is minimized. That results in less steering effort on the driver’s part and less sensitivity to braking inputs.
Figure 7 - Diagram of Kingpin Inclination and Scrub Radius [4]
Camber Camber angle is the angle made by the wheel of an automobile; specifically, it is the angle between the vertical axis of the wheel and the vertical axis of the vehicle when viewed from the front or rear. If the top of the wheel is further out than the bottom (that is, away from the axle), it is called positive camber; if the bottom of the wheel is further out than the top, it is called negative camber [8]. Negative camber is useful to improve grip when cornering. A negative angle places the tire at a more optimal angle to the road and thus transmits the forces through the tire rather than across it. Negative camber also prevents the tire from rolling on itself and maximizes the contact area of the wheel and tire during cornering. When in straight-line acceleration, however, the greatest traction will be attained when the camber angle is zero and the tread is flat on the ground. Therefore when considering camber we must analyze both options and find a compromise between both because although it is possible to make an adjustable camber suspension, it is of greater difficulty.
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Figure 8- Camber [5]
Caster Caster angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car - an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical [9]. The caster angle is important to make the car easier to drive and improve stability. Excessive caster angle will make the steering heavy and less responsive; however, in racing large angles are used to improve camber gain in cornering. Once again, in our designs we will have to compromise and see which will be more efficient for our increased performance vehicle.
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Figure 9- Caster [6]
Toe Toe is the angle made by the wheel with respect to the longitudinal axis of the vehicle. Toe in, when the front of the tires are closer together than the rear of the tires, aids in straight line stability, but can hinder steering performance. Toe out on the other hand will improve the efficiency of the steering system.
Figure 10- Toe Angles [7]
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3.3 Design Analysis The front suspension is of the double wishbone type and has been designed to provide good camber change in both bump and chassis roll. The kingpin inclination was kept small in order to minimize the spindle length and scrub radius. It will activate its shock absorbers via a pull rod and rocker link. By utilizing a pull rod, it allows a lower mounting of the shock absorbers, aiding in lowering the Center of Gravity.
Figure 11- Example of Double Wishbone with Pull rods [8]
The rear suspension will consist of a design similar to the double wishbone setup, the Arning four-link suspension. It has a regular A-arm for the upper arm, but the lower arm is a two piece design. The lower ball joint is between frame and control arm, as opposed to between the control arm and wheel upright. Between the wheel upright and the lower control arm is an inclined axis that will induce toe in under jounce conditions and toe out under rebound conditions. This positions the wheels ideally to allow the rear wheels to aid in steering under normal chassis roll that occurs when the car is in a turn.
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Figure 12- Plan View of Arning Four-Link [9]
The analysis will be done using Adams/Car. From there, we can get the loads that the suspension arms will exert on the chassis. These loads can then be applied to the chassis in Ansys in order to optimize our chassis.
Static Camber Camber in Jounce Camber in Rebound Caster Spindle Length
-1.5˚ -2.92°/1.5‖ -0.8˚/1.5" 4˚ 0.13"
Kingpin Inclination
3˚
Toe In
0˚
Ground Clearance
1.5"
Static Roll Center Height
1.25‖
Table 6 - Front Suspension Geometry
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3.3.1 Braking Analysis Braking is a huge aspect of the formula car. The formula car must be able to brake very efficiently, as nearly every part of the competition involves braking. There is a test solely devoted to the braking capabilities of the car. Also the endurance race involves heavy breaking. We feel that the most efficient braking setup for this car will be to have brakes on both front wheels and one brake on the rear sprocket. The braking system must be controlled by a single control which will have two independent hydraulic circuits in case of a leak or failure. This system will allow the car to maintain braking power in the case of a leak or failure.
Figure 13- Wilwood Brake Caliper from Side Mount Car
Figure 14– Upright from Side Mount Car
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The components of the brake system will be taken from the 2005 side mount car. This braking system includes a Wilwood combination (seen above) “remote” tandem master cylinder, which meets the Formula SAE specifications [1], calipers with brake pads, rotors, brake lights, and steel braided Teflon hoses. As the side mount car has never been used, the braking system on it is brand new, which means that we will not need to purchase anything apart from braking fluid for the car. The brake rotors are made of hardened steel, which have been known to be very durable. As one of the major aspects of competition is the auto-cross and endurance. Wheels and Tires We have decided to use 13” rims, which according to Formula SAE rules [1] is permissible. In order to save money, we have decided to use the rims from the 2005 side mount car. These are 13” rims, with single bolt on. A picture of this rim can be seen below.
Figure 15– Center Locking Wheel off of 2005 Side Mount Car
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Our tire selection is based on many different factors. Due to the fact that we are are reusing the side mount cars rims, we are limited to 13” rims. This though is the preferred choice of many of the teams competing, and therefore it is not of any disadvantage to us. 13” rims are optimum for the performance of this car due to the overall weight. Another factor in tire selection is the width of the tire. The width is a very important aspect for the handling of the car. The width we are looking at, is something between 6.5” and 7.5”. Rims can usually take a certain range of tires width. The 6.5” width is good because it reaches operating temperature quickly while weighing only 9lbs. Lighter weight and quicker operating temperature compensate for better handling in the 7.5” tire, which weighs 13lbs. Tire selection is also based on weather. We must have tire compounds which can handle both wet and dry conditions. Our tires will be bought from either Goodyear or Hoosier. Goodyear offers this tire at a price of about $153, while Hoosier offers it at $133. Both companies offer very similar tires made up of the same compounds and thus it is only a matter of which company would sponsor us.
3.3.1.1 Braking Calculations Calculations based on 2007 REV Car [10] Brake Force Calculations Brake Pedal: Assume that the driver input force is 90 lb. Moment output from pedal:
360 lb
Moment (InputForce)(Distance) (90) (2) 180 lb in
4 in
The caliper: The calipers have two pistons that actuate the brake pads so the force is multiplied by 2.
F 2( P)( A) Where:
A
D 2 4
P: the pressure from the master cylinder 31
D: the diameter of the caliper FCaliper Force: the clamp load A: area of the caliper Rear Calipers:
A
(1.15) 2 4
1.04 in 2
FCaliperForce 2 325.79 1.04 677.64 lb The brake pads: There are two brake pads so the force is multiplied by a factor of two.
Rotor Force 2 (Caliper Force) ( ) Where: = coefficient of friction = 0.45 (good assumption for most race cars) Front: F 2 540 .24 0.45 486 .26 lb
Rear:
F 2 677.64 0.45 606.88 lb The rotor: The torque applied on the rotor acts on both side so the torque is multiplied by 2.
Torque (2)(Rotor Force)(d ) Where: d: The distance between the center of the rotation and the force to act at a point midway across the rotor face. Front:
T 2 486.22 5 4862.2 lb in Rear:
T 2 606.88 3.5 4248.16 lb in 32
The wheels and tires:
F
Torque r
Where: F: Force generated between the tires and road r: Rolling radius of tire Front:
F
4862.2 486.22 lb 10
Rear:
F
4248.16 424.82 lb 10
Acceleration calculation:
a
2( FFront wheel ) 2( FRear Wheel ) W
Where: a: Lateral deceleration F: Force generated between the tires and the road for the front and rear tires. Force is multiplied by a factor of 2 because there are 2 front and 2 rear tires. W= Total estimated weight of the car, which includes car and driver.
a
2(486.22) 2(424.82) 2.80 g 650
Stopping distance: 2
D
Vi 2a
33
Where: Si: the initial speed a: Lateral deceleration
Vi
80 mile 1 hr 5280 ft X X 117.3 ft / s hr 3600 s 1 mile
a 2.80 g X
D
32.14 1g
ft s 2 89.99 ft / s 2
117.32 76.45 ft 2(89.99)
3.4 Detailed Drawings
Figure 16– Front Suspension Drawing
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3.5 Budget Part
Unit Price
Quantity
Total
Manufacturer
Chromoly 4130 Tubing 5/8”OD x .058”Wall
$26.50/8ft
2
$51
Onlinemetals.com
Spherical Rod Ends(sizes vary)
$5-$10
32
$160-320
Aurora Bearing Company
13” x 7.5” Aluminum wheels
$215
4
$860
Keizer Aluminum
Hoosier 225/45/13 A6 Autocross Radials
$181
4
$724
Tirerack.com
Tapered roller bearings(wheel bearings)
$10-$20
8
$80-$160
Timken
Table 7– Initial Suspension Sub-Team Budget
3.6 Scheduling 3.6.1 Gantt Chart
Figure 17– Gantt Chart Suspension Sub-Team
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3.7 Conclusions This design should result in a sound suspension system for our formula car. Once the designs of the front and rear are complete, the analysis using Adams will begin in order to optimize the designs. It will provide optimum handling characteristics for weekend autocross racing. Independent suspension all around will provide good traction to get the power to the ground and help keep the driver in control of the vehicle at all times.
4.1 Drivetrain 4.1.1 Introduction The drive train encompasses all the components that power the car. It is paramount that the motor be reliable yet produces ample efficient power. The power produced from the motor must be transferred to the differential in a simple compact manner. Then the differential must transfer the power through the axles to the wheels. All these components must be carefully selected as to not absorb excessive power from the motor yet be strong enough to endure rigorous race conditions.
4.1.2 Purpose The Drive Train team is responsible for creating and transferring the power obtained from the engine, to the wheels with the highest efficiency possible. The ultimate purpose of team is to design and build the drive train itself which encompasses the engine and its necessary components, power transfer from the engine to the differential, power transfer from the differential to the wheels, and ultimately power transfer to the ground.
4.1.3 Goals The design objectives for the drive train team are comprised of: •
Obtaining maximum power output from the engine with all the restrictions in place.
•
Make an engine that is as fuel efficient as can be without sacrificing power. 36
•
Build a flexible engine that can be tuned for different aspects of competition.
•
Build a reliable and effective engine that can be easily repaired or replaced
•
Design the most effective way to transfer power from the engine to the wheels.
•
Obtain the best and most effective transmission.
•
Design the least expensive way of mounting the differential to the chassis.
•
Find the most efficient way of connecting the differential to the wheels.
4.1.4 Background The engine and power train components are vital to the success of any Formula SAE team. Evaluating the characteristics of the three most popular engines in past Formula SAE competition that comply with rule 3.5.1.1 started the engine selection process. They were evaluated on their power to weight ratio, complexity, availability, ease of modification and tuning. The most popular is the fuel injected inline four cylinder 600cc found commonly in road bikes. They‟re known for making the most power but are very complex to modify and tune. Next is the fuel injected v-twin 550cc which is also commonly found in road bikes. It shares the same characteristics listed above for the 600cc. Lastly a fairly new entry to SAE competition is the naturally aspirated single cylinder 450cc that can be found in late model motocross bikes. It is quickly gaining popularity due to its light powerful nature derived from its original purpose of extreme off road racing. All the motors have an integrated transmission, although the 450cc transmission has the closest gear ratios. This is ideal for the tight circuit the car will be competing on. Thus the 450cc engine is the first choice for the FIT 2009 Formula SAE car.
4.2 Design Objectives With the Max Power CRF523R ICE CUBE Big Bore/Stroker kit installed along with the other proposed performance modifications, Max Power reports an average of 70rwhp. This is an unrestricted power/weight ratio of 1.27 versus the 600cc at .92. Due to the 450cc being naturally aspirated it will most likely have a higher power loss ratio than the 600cc. Although the above power numbers are from well tuned motors which the team feels much more capable of tuning the 450cc.
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4.3 Design and Analysis Power Train Components:
Tri-pod housing & Spline Shaft Tri-pods Tri-pod Boot Tri-pod Axle Shafts (Axles) Chain & Sprockets CRF450R and Components CRF523R ICE CUBE Big Bore/Stroker Boyesen Hy-flo Water Pump Pro Circuit Stainless Valves Pro Circuits Camshaft Pro Circuit Valve Springs Hinson Clutch Basket Torsen T-1 Differential
4.3.1 Drive train Analysis Due to the success of its usage in most of the Formula SAE cars previously within other universities, the 2009 team continues to use the ―university special‖ limited-slip differential manufactured by Torsen Inc. The university special differential was derived from the center differential used in the 1988 Audi Quattro. With the purchase of the differential set, we receive the side gears, element gears and the planet gears which all make up the differential as well as the sealed differential gear case that holds all these gears in place. A key element in the selection of the Torsen T-1 differential selection is the Torque sensing also known as the Torque Biasing system. The torque that comes from the engine is continuously managed between the two axles and biased instantaneously according the variable road conditions. Another key element is the weight. Compared to the 2004 Florida Tech FSAE car which have used the Quaife Civic differential that is 13 lbs, the Torsen T-1 differential weighs about 7 lbs.
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Differential Candidate Torque Bias Limited Slip Weight Price
Quaife ATB yes yes 13 lbs $995.00
Torsen T-1 yes yes 7 lbs $495.00
Table 8 - Comparison of Quaife & Torsen T-1
Figure 18— Cutaway of differential (Torsen T-1) [11]
Some key specifications of the Torsen T-1 differential are as follows: Bias Ratio
3.0:1
Weight
7 lbs. 2 oz.
Lubrication
80W-90 GL5
Bolt Torque
35 ft-lbs
Table 9- Differential Specification [2]
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A depiction of the drive train system of the Florida Tech 2003 automobile is as follows:
Figure 19- Drive Train Prototype Florida Tech 2003 Car
4.3.2 Engine Choice A rendered model of the Honda CRF 450 engine is as follows as it is designed on PRO-E:
Figure 20–(a)Pro E model of CRF450R Engine Model
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Figure 21– Actual CRF450R[12]
Stock Power Output
53 Hp
Target Power Output
65 Hp
Weight
55lbs
Lubrication
Honda HP4
Table 10- Engine Specifications
The decision to go with the 450cc engine as opposed to the standard 600cc engine that has been used in the past was to lose some excess weight from the motor and still have decent power output. The smaller 450cc engine can fit much more compactly in the chassis resulting in a lower center of gravity and smaller wheelbase. Another benefit with the 450cc comes from the tuning of the motor. It utilizes a carburetor induction system which simplifies the complex fuel injection system of the 600cc motor. The simpler carburetor system will free up time for us to put into other aspects of the car that may need much more attention. We feel this setup will be competitive at competition when paired up with the design of our chassis.
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4.3.3 Transmission Analysis Our goal is to achieve a speed of 80mph. Looking at the speed calculations, we see that this car is capable of reaching a speed of 120mph with a final drive of 4.4. This top speed is high and therefore we can increase the ratio of the gear on the drive train in order to increase torque and acceleration which would be more useful to us than a high top speed. Below are the gear ratios of the CRF 450R: Gear Ratios 1 - 0.800 (27/15) 2 - 1.470 (25/17) 3 - 1.235 (21/17) 4 - 1.050 (21/20) 5 - 0.909 (20/22) Final Reduction 3.923 (51/13) Final Drive #520 T-ring sealed chain Below, we see that there are two tables plotted on the graph. The green plotted lines are the lines that show the regular gear ratios and final drive of the car. After careful research we realized that most teams set their final drive at 4.4:1. Final drive is the ratio between the sprocket attached to the engine and the sprocket attached to the drive train. Using the regular final drive calculation, our car would be able to hit speeds of up to 122mph. Although this is impressive, it is not the most efficient setup to run the car at. This is so because during competition the car is predicted to hit a top speed of about 70mph due to all the curves and the lack of straights. Therefore after further investigation, we have decided to increase the final drive to 7.2:1, which would give us a top speed of 82mph. This setup we feel is the best for the car, since in shortening the gears, we can hit optimum power more often and thus get the most out of our horsepower and torque. Looking at the dynamometer chart we found the optimum power to be between 7500rpm and 9000rpm. Our chosen setup is shown on the graph with the red lines.
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Table 11- Graph above shows regular and custom setup for the gear box of the car[13]
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Figure 22- Dyno chart for the CRF450R
Looking at the Dyno Chart above, we see that the optimum horsepower for our Formula car is between 7500rpm and 9000rpm. We can also see that the optimum torque for the car is between 7000rpm and 8000rpm. In order to get the most out of the engine we must set up the car so as to spend most of our driving time at these rpm‟s. This can be done due to the fact that top speed is not an issue. To do this we must shorten the gears and increase the final drive. Research has been done on this and the final drive of 7.2:1 has been decided.
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4.4 Detailed Drawings
Figure 23- Detailed Drawing of the Torsen T-1 Differential [12]
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4.5 Budget Drive Train Budget: PART
QUANTITY
COST
Tri-pod housing & Spline Shaft
4
$196.00 each
Tri-pods
4
$60.00 each
Tri-pod Boot
4
$36.00 each
Tri-pod Axle Shafts
2
$179.00 each
Plastic end pieces
2
$35.00 each
Torsen T-1 Differential
1
$490.00 each
Chain & Sprockets
3 sets
$389.99
TOTAL
$2495.99
Table 12 - Drive Train Budget
The parts associated with the drivetrain come from Taylor Race Engineering [14]. They carry a variety of different parts that are dedicated towards Formula SAE cars. Engine Budget: PART
QUANTITY
COST
CRF450R and Components
1
$1000.00
CRF523R ICE CUBE Big Bore/Stroker
1
$2650.00
Boyesen Hy-flo Water Pump
1
$189.99
Pro Circuit Stainless Valves
1 set of 4
$350
Pro Circuits Camshaft
1
$457.99
Pro Circuit Valve Springs
1 set of 4
$239.99
Hinson Clutch Basket
1
$209.99
TOTAL
$5097.96
Total Budget:
$7113.95
Table 13 Engine Budget
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Performance parts for the engine were sourced from Max Power Engines [15], which have a great selection of replacement parts for our engine choice. The performance parts listed above will increase the power output of the motor giving us a great advantage during competition.
4.6 Scheduling 4.6.1 Gantt Chart
Figure 24– Gantt Chart for Drivetrain Sub-Team
4.6.2 Milestones and Deadlines Decided on Torsen Differential Final drive ratio 3.25 Intake system Design Differential Prototype Order Radiator and Fan Intake system for 2009 car Final Power Train Design Completion
October15, 2008 October 20, 2008 October 29, 2008 November 5,2008 November 25,2008 December 1, 2008 December 10, 2008
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4.7 Conclusions The team feels confident in our drive train component selection. Due to the sheer simplicity and availability of the 450cc along with performance parts, we feel it will be a very competitive motor. By choosing a lighter motor, the overall handling of the car should benefit from the lower center of gravity. The chain drive will provide variable light weight power transmission to the well proven Torsen differential. This drive train is very light weight and simple, yielding better performance and more time available for testing.
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5.1 Driver Interface 5.1.1 Introduction and Purpose The main purpose of this sub team is to provide safety to the driver and also to provide the car with an efficient steering system which is crucial for one of the competition‟s disciplines. The steering system is a vital component of a car as well as the driver‟s interface. The purpose of this sub team is also to provide the best interface possible between the driver and the car.
5.1.2 Goals Our goal is to make a car that can turn with the smallest curvature angle possible. Indeed, during the competition, one of the disciplines is a short circuit that the car should achieve in which the turns are very short and the wideness of the path is small. The driver should have the best driving position possible and be able to kill the engine easily. The wheel also needs to be taken off with no effort in case of emergency and the driver needs to get off the car. Thanks to all the parts we can get from previous cars, we also want to keep the expenses in our sub team as low as possible.
5.2 Design Objectives Our main objective is to give the driver comfort and simplicity of controlling the vehicle. However, as we want to save money and be sure to finish the car in time, we do not plan to make the seat and pedal adjustable. We want to keep our design simple and to give the driver as much control as possible at a low cost. We want to do all of this without over viewing the driver‟s safety.
5.3 Driver Interface Design and Analysis 5.3.1 Accelerator and Clutch Pedals 5.3.1.1 Engineering Specifications The main design objective of design the acceleration and clutch pedals to work within the limits of the throttle body of the carburettor and the clutch. Also for the comfort of the driver, the pedals cannot interfere with the movement and placement of the driver‟s foot. While the pedals
49
need to fit within the dimensions of the vehicle, they also need to be mounted such that the travel distance of the pedals will work within the vehicle‟s cockpit.
5.3.1.2 Design History In designing the pedals and mounts, it was realized that the designs of both pedals would be easier if everything was kept as simple as possible. With the motor and transmission that the team decided upon, the accelerator and clutch are both cable driven. As designed on the side-mount car, the pedals could be mounted to the chassis with the cables mounted directly to the pedal assembly. This design was previously used on the side-mount project of the previous team. The previous team designed this pedal assembly with a spring to retract the pedal. An example of this can be seen in figure 23 as the accelerator pedal mounted on the side-mount project. Note as the previous team took a different route with the clutch pedal whereas the FSAE car will use this design for both the accelerator and clutch pedals.
Figure 25. Side-mount car pedal setup
5.3.1.3 Engineering Analysis With the pedal mounted on the chassis as shown above, the pedal will be easy to engineer and mount. Final tuning of the carburettor will determine how much pedal travel is needed to achieve the best results. Ideally, the pedals should not travel very far. The goal of the overall design is to have a pedal that rotates between 45 and 60 degrees from the pivot point to minimize the linear distance of pedal travel but to give the driver more control and half throttle and half clutch. Pedals are useless without control up to their fully extended positions. Spring forces to return the pedal to its original position should be high enough to return the pedal quickly but at the same time not interfere with the amount of force the driver needs to exert to use the pedal. In addition
50
to these decisions, the pedal area can be altered allowing the driver to move between pedals effortlessly and not have to worry about hitting the wrong pedal.
5.3.1.4 Material Study The materials chosen for this design should accompany the simplicity of the engineering. The materials must be readily available and easy to manufacture. The material which would suit the need is aluminium. Aluminium is light weighted, strong, easy to machine and inexpensive. Nuts and bolts to mount the pedal assembly will be made of steel and can easily be found at the local hardware store for a very low price.
5.3.2 Brake Pedal 5.3.2.1 Engineering Specifications The engineering specifications of the brake pedal are very similar to the accelerator and clutch pedals. For the comfort of the driver, the pedal cannot interfere with the movement and placement of the driver‟s foot. The pedal will also need to fit within the dimensions of the vehicle and needs to be mounted such that the travel of the pedal will not interfere with anything.
5.3.2.2 Design History As designed on the side-mount car, the pedal assembly will be mounted to the floor plate of the chassis with a hydraulic reservoir. A brake pedal similar to the accelerator and clutch pedals could not be utilized because the team chose a hydraulic system over a cable system. The brake pedal assembly can be seen in figure 23 between the accelerator and clutch pedals.
5.3.2.3 Material Study The brake pedal assembly from the side-mount car is a Wilwood Engineering brake pedal with optional dual master cylinders. As shown in figure 24, the Wilwood brake pedal is adjustable and has an brake bias adjuster to fine tune braking between the front and rear wheels. The figure also shows the dual master cylinders mounted behind the pedal to reduce the overall room the assembly.
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Figure 26 Wilwood Dual Cylinder brake assembly [2]
5.3.3 Steering Wheel 5.3.3.1 Engineering Specifications The steering wheel for this vehicle needs to meet two specifications. The steering wheel design needs to be easily removable so that the driver can exit the vehicle quickly in case of emergency. Also, the steering wheel needs to be able to turn a full rotation easily without interfering with the driver. The driver needs to be able to turn the steering wheel one full rotation easily or the performance of the car will be limited.
5.3.3.2 Design History The steering wheel went through a few transformations in its design. Originally, a racing steering wheel was going to be purchased along with a quick release hub. To keep costs down, a standard round wheel would have been used with a very simple hub. The decision to reuse the steering wheel on the side-mount project became a possibility as well. This decision was thrown away when the steering wheel was determined cheap and poorly constructed. Figure 25 shows the steering wheel of the side-mount project.
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Figure 27Steering wheel of the side-mount
The final decision was to engineer one about 12 inches in diameter. A Formula style steering wheel will be constructed with rounded edges for easy driver manoeuvrability and non-rounded portions on the top and bottom to give the driver more room in the cockpit.
5.3.3.3 Material Study The material selected for the steering wheel is aluminium; the use of rubber grips has not been decided yet. Aluminium was selected for the steering wheel because it needs to be light weight and durable. The steering wheel will need to be removed often and a heavy steering wheel will be detrimental and unnecessary. A light weight aluminium wheel will also be easy to manufacture and ease the steering of the car. A pin will be used to keep the steering wheel attached to the shaft. The pin will be machined out of steel because it‟s strong and readily available. Other ideas for the pin include a ring that is easy to grasp so the driver can remove the pin quickly in case of emergency.
5.3.4 Steering Rack 5.3.4.1Engineering Specifications The design objective of the steering rack is to steer the car with minimal effort. For the ergonomics of the driver, the steering rack needs to have a ratio high enough to quickly steer the wheels but low enough that the driver has control of the car at all times. Also, the steering rack needs to be able to be small and light enough to mount within the car and cannot be detrimental to the overall performance.
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5.3.4.2 Design History Steering racks are difficult to manufacture and the purchase a pre-made rack was decided from the beginning. However, we also had the option of reusing the steering rack from the side-mount project, which had been mounted to the car vehicle but never used. This steering rack, as pictured on the side-mount car in figure 26, has the gearing ideal for the competition and although it needs to be well lubricated, suits our needs.
Figure 28-Steering Rack of the side-mount
5.3.5 Driver’s Seat 5.3.5.1 Engineering Specifications A driver seat has to accommodate for the driver comfort and ergonomics. The weight of the seat also should not weigh down the car.
5.3.5.2 Design History The design for the actual seat had been up in the air for awhile. The original plan was to reuse the seat from the side-mount project, the plans changed, however, when it was realized that someone had already reused the seat. Another idea was to make a seat out of fabric, but this was deemed unsafe and impractical. The final decision was to purchase a light weight seat.
5.3.5.3 Material Study There are many seats on the market for the type of vehicle our team is building. Generally, all of the seats are made of either some form of plastic or fibreglass. These two materials are light weight and somewhat flexible for comfort. The Tillet T8 seat shown in figure 27 is a good 54
example of what we are looking for. Racing seats such as the T8 generally range from 150 to 300 dollars.
Figure 29Tillet T8 Racing Seat [1]
5.3.6 Instrumentation 5.3.6.1 Engineering Specifications Instruments to measure parameters of race cars come in all shapes and sizes with different sensitivities. Finding instruments to monitor the performance of our vehicle generally comes down to compact, accurate gauges that are inexpensive.
5.3.6.2 Design History We will not be able to manufacture our own instruments, however, we will be able to purchase them and wire them into a cluster. The gauges needed for this vehicle will probably consist of a tachometer, coolant temperature, oil temperature, battery voltage, and speedometer. Summit Racing manufactures compact and accurate gauges which were featured on the side-mount project. Figure 28 shows the condition of the gauges. Notice the gauges are new and never mounted. Overall, instrumentation will cost a few hundred dollars.
55
Figure 30Summit Racing gauges
5.3.7 Safety Equipment 5.3.7.1 Engineering Specifications For safety requirements, the driver must comply with the safety guidelines of the Formula SAE rules as stated in Article 17. The driver is required to have a helmet, fire suit, gloves, goggles or face shields, and shoes. Specifications are as follows: Helmet - Snell M2000, SA2000, M2005, K2005, SA2005 - SFI 31.2A, SFI 31.1/2005 - FIA 8860-2204 - British Standards Institution BS 6658-85 types A or A/FR rating Fire Suit - SFI 3-2A/1 (or higher) - FIA Standard 1986 - FIA Standard 8856-2000 Fire resistant gloves and shoes with no holes Goggles or face shields made of impact resistant materials A harness of 5 points or more made of Nylon or Dacron polyester.
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5.3.7.2 Material Study 5.4 Engineering Drawings
Figure 31- Wilwood Pedal [2]
5.5 Budget As we want to keep the price low in this sub team, we are going to use a lot of parts that come from the previous cars. More specifically, the wheel, the seat, the pedals, the driver’s suit, and the steering system can be reused. But certain parts or materials have to be bought, like the firewall material to protect the driver from the fuel container and the engine. The mirrors will also have to be bought for driver visibility. A new belt should also be bought for better safety. However, the head restraint does not have to be pursued as we can only buy the material and build it ourselves. Some shield component, like steel or aluminum must be used to protect the driver from any sharp components, like the suspensions but more importantly the steering system.
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BUDGET GLOVES
Pro Series Glove PosiGripTM Driving Gloves FormulaGrip Driving Gloves
$114.95 $69.95 $89.95
SHOES
Heatshield Speedway Driving Shoes Cool Max Socks K Mid Sparco
$154.95 $16.00 $109.00
RESTRAINTS
Formula Car 6-Way 55 in Seat Belt Roll Bar V Harness All Bolt In 55 in Floor Mount Seat Belt Pull Down Y Harness
$199.95
HELMET
SUIT
Helmet Skirt Drag Bike Super Bandit - Nylon Liner Black Street Bandit - Nylon Liner - White R.J.S. Single-Layer Driving Suits Simpson Single-Layer One Piece Driving Suit
$179.95 $179.95 $49.95 $440.00 $399.00 $89.99 $169.95
FIRE H3R Perfromance Halguard Fire EXTINGUISHER Extinguisher
$119.95
SEAT
Tillet T8 Standard Clear Tillet T8 Standard Clear With Full Black Cover
$189.95
Pedals
Billet Pedal Set Pedal Grips
$229.00 $19.95
Materials
Aluminum Firewall
$229.00
~ $120 ~ $150
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lowest total
$1,402.79
highest total
$1,743.65
Unexpected expenses (~ +20%) TOTAL
~350 $1750 - $2100
Table 14- Parts Availabilities or Prices.
5.6 Gantt Chart
Figure 32– Gantt Chart Driver Interface Sub-Team
5.7 Conclusion In conclusion, the driver‟s interface is crucial for the well-behavior of the car. Even though the cockpit will be modest, the driver will be comfortable with a good visibility and the car will have a good steering. Everything will be studied, from the steering ratio to the position of the upper body and the legs. The SAE rules govern many aspects, but we will optimize the steering and driver position for the competition.
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6.1 References [1] 2009 Formula SAE Competition Rules and Regulations [2] www.asnt.org/ndt/primer3.htm [3] www.matweb.com [4] http://us1.webpublications.com.au/static/images/articles/i28/2895_15lo.jpg [5] http://www.desertrides.com/reference/images/terms/camber.gif [6] http://www.autowarrantybroker.com/_images/GlossaryImages/art_Caster.gif [7] http://driftjapan.com/blog/wp-content/uploads/2007/11/toe-in-vs-toe-out.jpg [8] http://documents.wolfram.com/applications/mechsystems/Examples/3DExamples/HTMLImages/Mech. Example.FrontSuspension.en/Mech.Example.FrontSuspension.en_a_1.gif [9] US Patent # 3189118 [10]http://www.my.fit.edu/rev [11]http://www.torsen.com [12]http://www.honda.com [13]http://www.fatboyraceworks.com [14]http://www.taylor-race.com [15] http://www.maxpower-engines.com
[16] http://www.crutchfieldracing.com/agoracart/agora.cgi?cart_id=6685105.18890*N_6MG2&xm =on&product=Chassis [17] https://www.safetysupplyamerica.com/c-750-fr-nomex.aspx [18] http://store.summitracing.com/ [19] http://www.pittsperformance.com 60
