Report on gear

P a g e | 1 Elecon Engineering Co. Ltd.

Introduction Gears are the most common means of transmitting power in mechanical engineering.There are tiny gears for devices like wrist watches and there are large gears thatsome of you might have noticed in the movie Titanic. Gears form vital elements of mechanisms in many machines such as vehicles, metal tooling machine tools, rollingmills, hoisting and transmitting machinery, marine engines, and the like. li ke. Toothedgears are used to change the speed, power, and direction between an input and output shaft.


A Gearbox Is Used in Turbines, Windmills, Grinders. Gears are used for increasing the torque of the source of rotary motion havinghigh angular momentum and low torque. This high torque is necessary forperformance of work. This phenomenon of increase in torque is called gearreduction and is brought about by coupling of a smaller gear called the pinionwith a larger gear. This results in reduction of torque at the expense of angular momentum. Such a gearbox is called a reducer. One more application ofgears is to change the axis or plane of rotary motion with or without gearreduction.When you open a gearbox you will see that the inner construction is verysimple. Inside you will find two gears coupled with one another. The gearsmay be of spur, helical, cycloid, worm or bevel type. In case of gear reduction,the diameter of the output is larger than that of the input gear. If only a changein direction is required, the size of the gears is the same. Spur gears are usedfor heavy load but are noisy. If the load is comparatively lesser, helical gearsare preferred as they are silent in operation due to gradual engagement. Ifchange of plane of rotation is required, hypoid gears are used.The gear may be either of metal or plastic. This entire arrangement isenclosed in metallic or plastic housing. The point of contact of the gear teethis well lubricated with gear oil. The gear oil must be very clean and free ofabrasive materials to avoid wearing of the gears.A gearbox is used in turbines, windmills, grinders, etc. to change the directionof the rotary motion. In automobiles a gear box is used for transfer of to powerof the engine to the wheels through a differential.

Factors to Keep in Mind in Gear Design    

Advantages of Gear Technology Gear Ratio Speed Reducers, Gearboxes, and Gear-Heads Design of Gear box


Factors to Keep in Mind in Gear Design Sometimes in gear design (for e.g. in the caseof spur gears, i.e. driver and driven) gears areto be designed for a specific velocity ratio anddistance between central shafts. For thepurpose of understanding this gear designbetter, let

:x = Distance between the centers of two shafts N1= Speed of the driver T1= Number of teeth on the driver d1= Pitch circle diameter of the driver N2 T2 and d2= Corresponding values for the driven or follower, and Pc= Circular pitch We know that the distance between the centres of two shafts, x=(d1+ d2)/2 and speed ratio or velocity ratio, N1 /N2= d2 /d1= T2 /T1 From the above equations, we can calculate d1and d2(or T1and T2) and the circular pitch (Pc). The values of T1and T2as obtained above, may or may not be whole numbers. But in gear design, since the number of teeth is always a whole number, a slight alteration must be made in the values of x, d1, and d2, so that number of teeth in the gear design is a complete number.


Advantages of Gear Technology The advantages of gear technology over other transmission means are:

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Gear technology gives positive drives and constancy of speed ratio without any slippage

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In Gear technology, the drive is very compact due to short center distances in such drives.

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Gear technology has high efficiency, service, and simple operation.

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Gear technology drives are capable of driving loads subjected to shock at speeds up to 20 m/s

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Maintenance of gear technology drives is inexpensive and if properly lubricated and operated, gear drives have the longest service life compared to other drives.

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Gear technology can be used where precise timing is desired.

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Gear technology can drive much heavier loads than other drives.

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Gear drives can be used for a wide range of transmitted power


Gear Ratio The gear ratio of your transmission, timing belt/chain and even your analog clock are what is responsible for rotational movement and the speed each piece or part achieves. Setting the correct gear ratio is vital, especially in the automotive industry. The wrong gear ratio will rob you of power, performance and even keep your vehicle from running at all, in the case of a timing belt of chain. If you've ever seen two gears working together, one turning the other as the teeth of the two gears mesh, you've seen a perfect example of gear ratio. This complex sounding conundrum is nothing more complex and complicated than the teeth of two gearsmeshing as they turn. It can also mean two sprockets connected with a chain or twopulleys with a drive belt. The best example of the sprockets and chain combination isprobably the standard timing chain. This vital piece of engineering is the driving forcebehind most modern vehicles, though timing belts are still used by somemanufacturers.A correct gear ratio is the driving force behind anything that contains rotational motion.Engines, transmissions, clocks and even windup toys use gears with the correct gearratio to produce the motion needed to turn whatever needs to be turned. Whether it'sbelts and drive shafts or tiny plastic axles and wheels, the correct gear ratio is incrediblyimportant. One of the best examples of getting the correct gear ratio would be replacinga timing belt. If the proper teeth are not selected when putting the new timing belt backon, the vehicle will be out of time. In short, it will run either very poorly, or not at all.That's because the pulleys and gears must meet at exactly the right point for therotation to match. If the rotational speed of the gears or pulleys doesn't match then youhave the incorrect gear ratio.Gear ratio is also used to increase the speed of gears and pulleys. If you have a largegear turning a smaller gear, the gear ratio will increase the rotational speed of the smallgear or pulley, dramatically. A gear ratio is written as any mathematical ratio: 2:1, 3:2,etc. In an example, if the large pulley rotated once per every two revolutions of the smallpulley, you would have a gear ratio of 2:1. Gear ratio is an observable factor, as well;look under your hood sometime, or inside a clock or anything else containing gears;you'll see that larger pulleys and gears usually turn more slowly than their smallercounterparts. This knowledge is used to create high speeds within engines andtransmissions.Gear ratio and teeth on the gears are inextricably related. If it weren't for the teeth onthe gears, slight differences in circumference and other manufacturing inconsistencieswould lead to an incorrect gear ratio inevitably. Since the majority of gears use teeth,those inconsistencies don't matter; the teeth make up the difference and provide for alack of slippage. Pulleys, on the other hand, are frequently the same size and have arubberized, or non-slip, outer covering. This combines with the autotensioner to keepthe belt firmly seated around the pulley, rather than dangling down below the vehicle.Gear ratio within a transmission is incredibly important. Gear ratio is what's responsiblefor your vehicle's acceleration and top speed. Both wide and close gear ratios havebenefits that are inherent to that type, though most modern transmissions do a good jobof running the middle ground between these two extremes.


Speed Reducers, Gearboxes, and Gear-Heads Speed reducers are a combination of sets of gears as found in gearboxes and gear-heads, having shafts and bearings, assembled in an enclosed metal housing. The purpose of application of speed reducers is to convert input to a known output speed, there-by reducing the RPM at the output with increased torque. In its present form of new invention, the multiple speed gear reducer has an input shaft and a power output shaft, with a series of train of load sharing gears interconnecting the shafts at the output and input. The gear trains also interconnect two or more reaction gears of different sizes. These reaction gears are of different sizes, which are connected to the input shaft coaxially, producing relative rotational motion between the gears and the input shaft. These are then operatively connected to the gear trains. Each of the reaction gears has a clutch, which selectively restricts the gear trains to attain apre determined gear reduction ratio between the input and output shafts. There are separate coaxially arranged sleeves put around the input shaft, which is used to mount these reaction gears. The clutches on the sleeves control the reaction gears in order to maintain the specific gear ratio. Speed reducers are used in machine tools to set the different speed that is required for different kinds of machining. The common types of reducers that are used are the pulley pairs of different diameter, gearboxes, and stepped electric motors. Gear boxes which are termed as speed reducers are generally found in different machine tools, automobiles, transmission products, cranes and hoists, etc. The most common type of speed reducers are:       

Worm gear reducers. Bevel gearboxes. Helical gear reducers. Parallel shaft gear reducers. Planetary gear reducers. In-line helical reducers. Right angle reducers.

Gearboxes or speed reducers are constructed out of high performance hardened and toughened shaved gears, which have been designed to operate smoothly with loss of little power. The gears and the shafts are assembled in a metallic housing using shafts and bearings. The input to the speed reducer comes from an electric motor shaft. The gears are of different sizes, having variety of numbers of teeth and coming in different diameter. The gear combination that is required to be meshed into each other is selected by the set of levers and clutches, and this combination enables the speed reducer to run in varied fixed steps. The output of this speed reducer came from the output shaft. The speed reducer needs to be thoroughly lubricated for the system to run smoothly. In designing a speed reducer, the number of teeth of that of the larger gear is divided with that of the smaller gear. This ratio will provide you with the one you want in a helical and bevel gear set. For example, with the large gear having 28 teeth, if the smaller one has 14, the speed reducer ratio between the input and output would give you a ratio of 2:1.


Gearbox Design Prime movers such as Electric motors, internal combustion engine, steam engines and turbines produce rotary motion at certain speeds and with certain torques at optimum efficiency. The motion produced is rarely equal to the motion required to do the necessary work and gear trains are required to translate the motion economically at maximum efficiency. It may be possible to use a low cost method of translating the motion e.g a timing belt vee belt or chain transmission system. However these methods are limiting in their scope and are subject to regular maintenance and replacement. The engineered gearbox generally provides the optimum solution. Many components provide motorized gear units with the electric motor mounted directly onto a gearbox providing the drive conditions (torque and speed) exactly as required by the user. Once installed to the manufactures instructions the only maintence required is regular lubrication. Gearboxes can be engineered to allow gear ratio changes to enable output shaft speed while keeping the input speed and torque at the same value. The primary advantage for using a gearbox for changing speed is to enable the full power to be transmitted at the different speeds. Electric motors and other prime movers are rated for maximum torque at the optimum speed. If the speed is reduced using electronic controls the resulting developed torque is not proportionally increased. Gearboxes also allow the input shaft and the output shaft to be different directions.


Simple Drive Train Rules 1) For any pair of meshing gears the angular velocity ratio is given by w1/w2=w z1/z2=w d1/d2

W1=input speed(rad/s) W2=output speed(rad/s) Z1 number of teeth on input gear Z2 number of teeth on output gear D1 pitch circle dia of the input gear D2 pitch circle dia of the input gear (The sign is-(Reversing)if both gears are external and +(same direction)if one gear is ring()internal gear) 2) For a train of gear wheels the overall angular velocity ratio is given by w2/w1 =w product of teeth nos driving gear/product of teeth no’s driven gears W product of pitch diameters(driven gears) The sign is-(Reversing) if there are an odd number of pairs of external gears Gearbox Design Features The design of the gearbox includes the following features.              

Input and output shaft relative position and orientation Support of external forces on shafts Design and rigidity of casing Type, dimensions and strength of gears Method of changing speed direction if required Design and strength of gear shafts Gearbox bearings Gearbox Seals Lubrication Noise and vibration Couplings to shaft Fixing support of gearbox Heat dissipation Maintenance provisions


Gearbox Examples 

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A gearbox is loosely defined as an enclosure for housing gears. Examples of gearboxes are numerous and some are listed below: Watch mechanism Bicycle axle gear (Sturdy Archer-3 speed) Sprocket to wheel axle -(Sturdy Archer-3 speed)

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Power tool gear units – allowing speed reduction, change and reversing

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Automobile synchromesh gearbox -5 speed + reverse – Engine to drive shafts

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Machine tool integral – Electric motor drive to spindle and travelling motions

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Wind turbine gearbox- Turbine to generator

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Steam turbine – speed reduction turbine to generator

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Marine – Gearbox – turbine diesel prime movers to Prop shaft

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Cranes –Gearbox using for lifting and travelling motions

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These are all specialized applications and the notes on this page relate to gear units manufactured as separate units for mounting in transmission systems. The normal method of fi xing an enclosed gearbox in industry is to mount it on a rigid horizontal baseplate designed to absorb vibration. The rotary motio n is transf erre d to the i nput sh aft an d fro m the output shafts via flexible couplings. There are a number of variations as listed below:


Mounting    

Foot mounted on vertical surfaces Foot mounted below horizontal surface Flange mounted onto the prime mover Shaft mounted with a torque arm to prevent rotation of gearbox

The sketches below show examples of gearboxes mounted in different ways. These are only illustrative sketches and should not be considered as gearbox designs.


Gearbox Casing The large gearbox casings are generally from cast iron or steel.cast iron is a rigid material with excellent vibration damping properties. Fabricated steel gearbox are used for small batch quantities. Gearbox used for the transmission in vehicles are often made form cast aluminium this is primarily to save weight. The tiny gearbox units are made from a variety of material including cast zinc alloys. The important criteria in the gearbox design are listed below.   

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Inclusion of safe lifting points to allow installation Support of the shaft bearings and hence the gear loadings; The transfer of the developed gearforces to supporting structure or further drive element; Containment of lubricant and exclusion of foreign matter; Providing a safety and noise barrier; Dissipation of the heat generated by gear friction Aiding testing, installation, and maintenance by contain ing all element in one unit; Providing convenient access to internals for inspection &maintenance Aesthetic benefits Enable accessible location of nameplate with all of the gear unit details


Gearbox shafts A variety of shaft designs are available including the following     

Plain shaft with keyway Plain shaft suitable for Friction drive coupling system Splined shaft Hollow shaft with internal keyway Flange

The selection of the drive shaft system is generally based on space consideration, on the design of the prime mover of the driven component and on the loading pattern. A proprietary gearbox is designed to best fit in with the existing drive arrangements. Shaft Orientation The shafts transfer of motion to and from a gearbox can be supplied in a variety of designs some of which are listed below:   

Inline shafts…..Epi-cyclic, spur, helical, harmonic Parallel shafts….spur, helical Shafts at angles but non intersecting… helical, worm,, hypoid, spiroid gears.

P a g e | 13 Elecon Engineering Co. Ltd. Elecon’s Gearboxes

Elecon's Gear Division is acknowledged in the industry as the most modern in the country. More then 85% of machinery and testing equipment is computer controlled, ensuring a high degree of precision in the manufacture, and testing of gear components to DIN / AGMA international specifications. Elecon is one of the very few companies to deploy the 3 Axis Co-ordinate Measuring Machine. Apart from a large concentration of Computerized Numerically Controlled (CNC) Machines, Elecon has sophisticated gear profile testing machines, full-fledged testing/calibrating lab and Vacuum Spectrometers to check chemical analysis of raw material. Besides, there are flexible machining systems; a battery of state-of-the-art, quality control equipment, online computerized inventory control, production planning, execution programmers managed using state of the art ERP software. Deploying modern technology through CAD / CAM in engineering and manufacture on a continuous basis is a thrust area at Elecon.


Turbo Gear Unit

Elecon engineering has expertise in designing and manufacturing high speed, high power gear boxes. TA - Turbo Gear Unit (Double Helical Gear) The TA TURBO Gear unit is a single stage step-up or reduction Gear unit with horizontally offset. It is designed as a double helical Gear unit. High Gearing quality and tooth flank modification adapted to actual tooth load allow for extremely high pitch line velocity. Double helical Gear units are simple to design & manufacture and compact. Double helical gearboxes are more efficient than single helical gear boxes. This Gear unit is used in high speed plants such as turbo generators, turbo Compressor, Boiler feed pump application etc.

TAD - Turbo Gear Unit (Single Helical Gear) The TAD turbo Gear unit is a single stage step-up or reduction gearbox with horizontally offset. It is designed as a single heical gearunit.to the thrust collar technique.The tooth thrust resulting from helical teeth is being compensated through thrust collar.


Applications 1. 2. 3. 4. 5. 6. 7. 8.

Gas Turbine Steam Turbine Pumps Compressor ID/FD Fan Blowers Test Rig Special Application.

Design Design is based on RENK guidelines .Elecon had co-operation with RENK for High speed gear Boxes from 1988 to 1994. Design Standards 1. 2. 3. 4.

AGMA - 6011 AGMA - 6010 API-613 ( 5 TH EDITION ) API-677 ( 2 ND EDITION )

Achievement Elecon has manufactured gearboxes upto 23,000 kw and speeds upto 10,000 rpm. Retrofit / Repair Apart from supplying new gearboxes, Elecon can provide retrofitting / repair of any other make of the gears. Services 1. Elecon can supply complete new gearbox on existing foundation by keeping center distance and center height same as of existing one. 2. Manufacturing of only gear wheel and pinions to fit in the existing casing . 3. Elecon can provide new gearbox/ gear internals with upgraded power or change in ratio to fit on A) Existing foundation B) Existing center distance C) Existing center height 4. Overhauling of any make of the gearBox. 5. Ongoing service support


ER - Series

Specifications Size

4" to 17"

Rating

1.1 to 350 kW

Mounting and change of Shaft Handling

Achieved easily and quickly without dismantling the gear case.

Applications

Heavy duty stirrer gear units Cooling Tower gear units Double Reduction: Worm-worm, Helical-worm, Worm Geared motors.


Reverse Reduction Gearbox

Marine Reverse Reduction Gearbox for Fixed Pitch Propeller Drive Description Features

Gearbox with inbuilt clutch

Advantages

Compact and adaptable with Engine

Technical Specifications

AWS 40 suitable for 346 kw power & AWSF 80 suitable for 627kw input power

Product Application

Sea Vessels such as harbor tugs, fishing vessels, pusher boats, pilot boats, life boats, ferries, yatches

Range

Available in range of 100 kw to 3800 kw for reduction ratios from 1.6 to 7


CODOG Marine Gear Box

CODOG Marine Gear Box Description Features

Double Helical profile ground gears with inbuilt clutch

Advantages

Low Noise and Vibration

Technical Specifications

CODOG Marine Gear Box

Product Application

Bigger Ship

Range

Custom built to client`s specifications

Report on gear

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