termpaper mec101

8/8/2019 TermPaper MEC101

1/20

TERM PAPER OF 4TH SEMESTER 2010

MECHANICAL SCIENCES

MEC101

TOPIC: DIFFERENT TYPES OF GEARS AND THEIR APPLICATION IN

AUTOMOBILES

DOA: 13th March 2010

DOS: 11th May 2010

Submitted to: Submitted by:

Mr.Gagandeep Singh Mr. William Anthony

Deptt. Of Mechanical Science Rollno:RD1803B30

Regd no.:10805460

B.Tech M.Tech(Cse)

ACKNOWLEDGEMENT


2/20

I would like to express my gratitude for the many helpful comment and

suggestions .I have received over the last few days regarding the expository and

critical expects of my term work and especially for those comments which bear

directly or may various argument for the center thesis of term work.

Most importantly I would like to thank my HOD (head of department) and my

teacherMr.Gagandeep Singh for his days of supervision. His critical commentary

on my work has played a major role in both the content and presentation of our

discussion and arguments.

I have extend my appreciation to the several sources which provided various kinds

of knowledge base support for me during this period.

Last and not the least my God and my parent helped me to overcome the problem

while preparing this project.

WILLIAM ANTHONY

TABLE OF CONTENTS


3/20

HISTORY OF GEARS

INTRODUCTION TO GEARS

COMPARISION WITH OTHER DRIVE MECHANISMS

GEAR DESIGN

GEAR MANUFACTURE

TYPES OF GEARS

APPLICATION OF GEARS IN AUTOMOBILES

GEAR MODEL IN MODERN PHYSICS

HISTORY OF GEARS

Gears have existed since the invention of rotating machinery. Because of their force-multiplying

properties, early engineers used them for hoisting heavy loads such as building materials. The

mechanical advantage of gears was also used for ship anchor hoists and catapult pre-tensioning.


4/20

Early gears were made from wood with cylindrical pegs for cogs and were often lubricated with

animal fat grease. Gears were also used in wind and water wheel machinery for decreasing or

increasing the provided rotational speed for application to pumps and other powered machines.An early gear arrangement used to power textile machinery is illustrated in the following figure.

The rotational speed of a water or horse drawn wheel was typically too slow to use, so a set of

wooden gears needed to be used to increase the speed to a usable level.

An 18th Century Application of Gears for Powering Textile Machinery

The industrial revolution in Britain in the eighteenth century saw an explosion in the use of metal

gearing. A science of gear design and manufacture rapidly developed through the nineteenth

century.

Today, the most significant new gear developments are in the area of materials. Modern

metallurgy has greatly increased the useful life of industrial and automotive gears, and consumer

electronics has driven plastic gearing to new levels of lubricant-free reliability and quietoperation.

INTRODUCTION TO GEARS

A gear is a rotatingmachine part having cut teeth, or cogs, which mesh with another toothed part

in order to transmit torque. Two or more gears working in tandem are called a transmission andcan produce a mechanical advantage through a gear ratio and thus may be considered a simple
http://en.wikipedia.org/wiki/Rotatinghttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Mechanical_advantagehttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Rotatinghttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Mechanical_advantagehttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Simple_machine


5/20

machine. Geared devices can change the speed, magnitude, and direction of apower source. The

most common situation is for a gear to mesh with another gear, however a gear can also mesh a

non-rotating toothed part, called a rack, thereby producing translation instead of rotation.

The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that

the teeth of a gear prevent slipping.

When two gears of unequal number of teeth are combined a mechanical advantage is produced,

with both the rotational speeds and the torques of the two gears differing in a simple relationship.

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as infirst gear, refers to a gear ratio rather than an actual physical gear. The term is used to describe

similar devices even when gear ratio is continuous rather than discrete, or when the device does

not actually contain any gears, as in a continuously variable transmission.

The earliest known reference to gears was circa 50 A.D. by Hero of Alexandria, but they can be

traced back to the Greekmechanics of the Alexandrian school in the 3rd century BC and weregreatly developed by the GreekpolymathArchimedes (287-212 BC).

A gear is a rotatingmachine part having cut teeth, or cogs, which mesh with another toothed part

in order to transmit torque. Two or more gears working in tandem are called a transmission andcan produce a mechanical advantage through agear ratioand thus may be considered a simple

machine. Geared devices can change the speed, magnitude, and direction of apower source. The

most common situation is for a gear to mesh with another gear, however a gear can also mesh anon-rotating toothed part, called a rack, thereby producing translation instead of rotation.

The gears in a transmission are analogous to thewheels in apulley. An advantage of gears is that

the teeth of a gear prevent slipping.

When two gears of unequal number of teeth are combined a mechanical advantage is produced,with both the rotational speedsand the torques of the two gears differing in a simple relationship.

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in

first gear, refers to a gear ratio rather than an actual physical gear. The term is used to describe

similar devices even when gear ratio iscontinuousrather than discrete, or when the device doesnot actually contain any gears, as in a continuously variable transmission.

COMPARISON WITH OTHER DRIVE MECHANISMS

The definite velocity ratio which results from having teeth gives gears an advantage over otherdrives (such as traction drives andV-belts) in precision machines such as watches that depend

upon an exact velocity ratio. In cases where driver and follower are in close proximity gears also
http://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Power_sourcehttp://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Wheelshttp://en.wikipedia.org/wiki/Pulleyhttp://en.wikipedia.org/wiki/Rotational_speedhttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Discretehttp://en.wikipedia.org/wiki/Continuously_variable_transmissionhttp://en.wikipedia.org/wiki/Hero_of_Alexandriahttp://en.wikipedia.org/wiki/Ancient_Greecehttp://en.wikipedia.org/wiki/Alexandrian_schoolhttp://en.wikipedia.org/wiki/Polymathhttp://en.wikipedia.org/wiki/Archimedeshttp://en.wikipedia.org/wiki/Rotatinghttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Mechanical_advantagehttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Power_sourcehttp://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Wheelshttp://en.wikipedia.org/wiki/Wheelshttp://en.wikipedia.org/wiki/Pulleyhttp://en.wikipedia.org/wiki/Pulleyhttp://en.wikipedia.org/wiki/Rotational_speedhttp://en.wikipedia.org/wiki/Rotational_speedhttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Discretehttp://en.wikipedia.org/wiki/Discretehttp://en.wikipedia.org/wiki/Continuously_variable_transmissionhttp://en.wikipedia.org/wiki/Continuously_variable_transmissionhttp://en.wikipedia.org/wiki/Traction_(engineering)http://en.wikipedia.org/wiki/Belt_(mechanical)http://en.wikipedia.org/wiki/Belt_(mechanical)http://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Power_sourcehttp://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Wheelshttp://en.wikipedia.org/wiki/Pulleyhttp://en.wikipedia.org/wiki/Rotational_speedhttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Discretehttp://en.wikipedia.org/wiki/Continuously_variable_transmissionhttp://en.wikipedia.org/wiki/Hero_of_Alexandriahttp://en.wikipedia.org/wiki/Ancient_Greecehttp://en.wikipedia.org/wiki/Alexandrian_schoolhttp://en.wikipedia.org/wiki/Polymathhttp://en.wikipedia.org/wiki/Archimedeshttp://en.wikipedia.org/wiki/Rotatinghttp://en.wikipedia.org/wiki/Machinehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Transmissionhttp://en.wikipedia.org/wiki/Mechanical_advantagehttp://en.wikipedia.org/wiki/Gear_ratiohttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Power_sourcehttp://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Wheelshttp://en.wikipedia.org/wiki/Pulleyhttp://en.wikipedia.org/wiki/Rotational_speedhttp://en.wikipedia.org/wiki/Continuoushttp://en.wikipedia.org/wiki/Discretehttp://en.wikipedia.org/wiki/Continuously_variable_transmissionhttp://en.wikipedia.org/wiki/Traction_(engineering)http://en.wikipedia.org/wiki/Belt_(mechanical)


6/20

have an advantage over other drives in the reduced number of parts required; the downside is that

gears are more expensive to manufacture and their lubrication requirements may impose a higher

operating cost.

The automobiletransmissionallows selection between gears to give various mechanical

advantages.

GEAR DESIGN

Gears have been around for hundreds of years and are as old as almost any machinery ever

invented by mankind. Gears were first used in various construction jobs, water raising devicesand for weapons like catapults.

Nowadays gears are used on a daily basis and can be found in most peoples everyday life fromclocks to cars rolling mills to marine engines. Gears are the most common means of transmitting

power in mechanical engineering.

Gears are used in almost all mechanical devices and they do several important jobs, but most

important, they provide a gear reduction. This is vital to ensure that even though there is enough

power there is also enough torque(is a movement of force).

GEAR MANUFACTURE
http://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Transmission_(mechanics)http://en.wikipedia.org/wiki/Transmission_(mechanics)http://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Transmission_(mechanics)


7/20

The materials that are used for gear manufacturing depend massively on the conditions that the

gears will be operating under, conditions like wear and noise etc. Gear manufacturers use

metallic or non-metallic materials.

The Metallic materials used in gear manufacture are normally available in cast iron, steel and

bronze. Steel is used when there is a need for a high strength design. But cast iron is mainly usedbecause of its good wearing properties, excellent machineability and the ease that complicated

shapes can be created due to the casting method.Castings are created by pouring molten metal

into a mould and once the metal as cooled it takes the shape of the mould.

The non metallic, materials used are generally wood, rawhide, compressed paper and synthetic

resins like nylon. These types of materials are generally used when there is a need for the

reduction in noise from the gears

TYPES OF GEARS


8/20

External vs. internal gears

Internal gear

An external gear is one with the teeth formed on the outer surface of a cylinder or cone.Conversely, an internal gear is one with the teeth formed on the inner surface of a cylinder or

cone. For bevel gears, an internal gear is one with the pitch angle exceeding 90 degrees. Internal

gears do not cause direction reversal.

Spur

Spur gear

Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk,and with the teeth projecting radially, and although they are not straight-sided in form, the edge

of each tooth thus is straight and aligned parallel to the axis of rotation. These gears can be

meshed together correctly only if they are fitted to parallel axles.

Helical
http://en.wikipedia.org/wiki/File:Spur_Gear_12mm,_18t.svghttp://en.wikipedia.org/wiki/File:Inside_gear.png


9/20

Helical gears

Top: parallel configuration

Bottom: crossed configuration

Helical gears offer a refinement over spur gears. The leading edges of the teeth are not parallel tothe axis of rotation, but are set at an angle. Since the gear is curved, this angling causes the tooth

shape to be a segment of ahelix. Helical gears can be meshed in a parallel or crossed

orientations. The former refers to when the shafts are parallel to each other; this is the most

common orientation. In the latter, the shafts are non-parallel.

The angled teeth engage more gradually than do spur gear teeth causing them to run more

smoothly and quietly. With parallel helical gears, each pair of teeth first make contact at a single

point at one side of the gear wheel; a moving curve of contact then grows gradually across thetooth face to a maximum then recedes until the teeth break contact at a single point on the

opposite side. In spur gears teeth suddenly meet at a line contact across their entire width causing

stress and noise. Spur gears make a characteristic whine at high speeds and can not take as much

torque as helical gears. Whereas spur gears are used for low speed applications and thosesituations where noise control is not a problem, the use of helical gears is indicated when the

application involves high speeds, large power transmission, or where noise abatement is

important. The speed is considered to be high when the pitch line velocity exceeds 25 m/s.[5]

A disadvantage of helical gears is a resultant thrust along the axis of the gear, which needs to beaccommodated by appropriate thrust bearings, and a greater degree ofsliding frictionbetween

the meshing teeth, often addressed with additives in the lubricant.

Double helical

Double helical gears
http://en.wikipedia.org/wiki/Helixhttp://en.wikipedia.org/wiki/Helixhttp://en.wikipedia.org/wiki/Noise_abatementhttp://en.wikipedia.org/wiki/Gear#cite_note-pitchlinespeed-4http://en.wikipedia.org/wiki/Thrusthttp://en.wikipedia.org/wiki/Thrust_bearinghttp://en.wikipedia.org/wiki/Thrust_bearinghttp://en.wikipedia.org/wiki/Sliding_frictionhttp://en.wikipedia.org/wiki/Sliding_frictionhttp://en.wikipedia.org/wiki/File:Herringbone_gears_(Bentley,_Sketches_of_Engine_and_Machine_Details).jpghttp://en.wikipedia.org/wiki/File:Helical_Gears.jpghttp://en.wikipedia.org/wiki/Helixhttp://en.wikipedia.org/wiki/Noise_abatementhttp://en.wikipedia.org/wiki/Gear#cite_note-pitchlinespeed-4http://en.wikipedia.org/wiki/Thrusthttp://en.wikipedia.org/wiki/Thrust_bearinghttp://en.wikipedia.org/wiki/Sliding_friction


10/20

Double helical gears, or herringbone gears, overcome the problem of axial thrust presented by

"single" helical gears by having two sets of teeth that are set in a V shape. Each gear in a doublehelical gear can be thought of as two standard mirror image helical gears stacked. This cancels

out the thrust since each half of the gear thrusts in the opposite direction. Double helical gearsare more difficult to manufacture due to their more complicated shape.

Bevel

A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevelgears mesh their imaginary vertexes must occupy the same point. Their shaft axes also intersectat this point, forming an arbitrary non-straight angle between the shafts. The angle between the

shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and

shaft axes at 90 degrees are called miter gears.

The teeth of a bevel gear may be straight-cut as with spur gears, or they may be cut in a variety

of other shapes. Spiral bevel gears have teeth that are both curved along their (the tooth's) length;

and set at an angle, analogously to the way helical gear teeth are set at an angle compared to spur

gear teeth. Zerol bevel gears have teeth which are curved along their length, but not angled.Spiral bevel gears have the same advantages and disadvantages relative to their straight-cut

cousins as helical gears do to spur gears. Straight bevel gears are generally used only at speedsbelow 5 m/s (1000 ft/min), or, for small gears, 1000 r.p.m.

Hypoid

Hypoid gear

Hypoid gears resemble spiral bevel gears except the shaft axes do not intersect. The pitch

surfaces appear conical but, to compensate for the offset shaft, are in facthyperboloids of

revolution. Hypoid gears are almost always designed to operate with shafts at 90 degrees.Depending on which side the shaft is offset to, relative to the angling of the teeth, contact
http://en.wikipedia.org/wiki/Right_circular_conehttp://en.wikipedia.org/wiki/Hyperboloidhttp://en.wikipedia.org/wiki/Hyperboloidhttp://en.wikipedia.org/wiki/File:Sprocket35b.jpghttp://en.wikipedia.org/wiki/File:Gear-kegelzahnrad.svghttp://en.wikipedia.org/wiki/Right_circular_conehttp://en.wikipedia.org/wiki/Hyperboloid


11/20

between hypoid gear teeth may be even smoother and more gradual than with spiral bevel gear

teeth. Also, the pinion can be designed with fewer teeth than a spiral bevel pinion, with the result

that gear ratios of 60:1 and higher are feasible using a single set of hypoid gears. This style ofgear is most commonly found in mechanical differentials.

Crown

Crown gears or contrate gears are a particular form of bevel gear whose teeth project at rightangles to the plane of the wheel; in their orientation the teeth resemble the points on a crown. A

crown gear can only mesh accurately with another bevel gear, although crown gears aresometimes seen meshing with spur gears. A crown gear is also sometimes meshed with an

escapement such as found in mechanical clocks.

Worm

Worm gear

Worm gears resemble screws. A worm gear is usually meshed with an ordinary looking, disk-

shaped gear, which is called the gear, wheel, or worm wheel.

Worm gears can be considered a species of helical gear, but its helix angle is usually somewhatlarge (close to 90 degrees) and its body is usually fairly long in the axial direction; and it is these
http://en.wikipedia.org/wiki/Escapementhttp://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/File:Worm_Gear_and_Pinion.jpghttp://en.wikipedia.org/wiki/File:Crown_gear.pnghttp://en.wikipedia.org/wiki/Escapementhttp://en.wikipedia.org/wiki/Screw


12/20

attributes which give it its screw like qualities. The distinction between a worm and a helical

gear is made when at least one tooth persists for a full rotation around the helix. If this occurs, it

is a 'worm'; if not, it is a 'helical gear'. A worm may have as few as one tooth. If that toothpersists for several turns around the helix, the worm will appear, superficially, to have more than

one tooth, but what one in fact sees is the same tooth reappearing at intervals along the length of

the worm. The usual screw nomenclature applies: a one-toothed worm is called single thread orsingle start; a worm with more than one tooth is called multiple thread or multiple start. The

helix angle of a worm is not usually specified. Instead, the lead angle, which is equal to 90

degrees minus the helix angle, is given.

In a worm-and-gear set, the worm can always drive the gear. However, if the gear attempts todrive the worm, it may or may not succeed. Particularly if the lead angle is small, the gear's teeth

may simply lock against the worm's teeth, because the force component circumferential to the

worm is not sufficient to overcome friction. Worm-and-gear sets that do lock are called selflocking, which can be used to advantage, as for instance when it is desired to set the position of a

mechanism by turning the worm and then have the mechanism hold that position. An example is

the machine head found on some types ofstringed instruments.

Non-circular

Non-circular gears

Non-circular gears are designed for special purposes. While a regular gear is optimized to

transmit torque to another engaged member with minimum noise and wear and maximum

efficiency, a non-circular gear's main objective might be ratio variations, axle displacement

oscillations and more. Common applications include textile machines,potentiometersandcontinuously variable transmissions.

Rack and pinion
http://en.wikipedia.org/wiki/Machine_headhttp://en.wikipedia.org/wiki/Stringed_instrumenthttp://en.wikipedia.org/wiki/Stringed_instrumenthttp://en.wikipedia.org/wiki/Stringed_instrumenthttp://en.wikipedia.org/wiki/Mechanical_efficiencyhttp://en.wikipedia.org/wiki/Ratiohttp://en.wikipedia.org/wiki/Oscillationhttp://en.wikipedia.org/wiki/Potentiometerhttp://en.wikipedia.org/wiki/Potentiometerhttp://en.wikipedia.org/wiki/File:Non-circular_gear.PNGhttp://en.wikipedia.org/wiki/Machine_headhttp://en.wikipedia.org/wiki/Stringed_instrumenthttp://en.wikipedia.org/wiki/Mechanical_efficiencyhttp://en.wikipedia.org/wiki/Ratiohttp://en.wikipedia.org/wiki/Oscillationhttp://en.wikipedia.org/wiki/Potentiometer


13/20

Rack and pinion gearing

A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely largeradius of curvature. Torque can be converted to linear force by meshing a rack with a pinion: the

pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to

convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks alsofeature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable

set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears ofparticular actual radii then derived from that. The rack and pinion gear type is employed in a rackrailway.

Epicyclic

In epicyclic gearing one or more of the gearaxes moves. Examples are sun and planet gearing(see below) and mechanical differentials.

Sun and planet
http://en.wikipedia.org/wiki/Steeringhttp://en.wikipedia.org/wiki/Rack_railwayhttp://en.wikipedia.org/wiki/Rack_railwayhttp://en.wikipedia.org/wiki/Axishttp://en.wikipedia.org/wiki/Axishttp://en.wikipedia.org/wiki/File:Epicyclic_gear_ratios.pnghttp://en.wikipedia.org/wiki/File:Rack_and_pinion_animation.gifhttp://en.wikipedia.org/wiki/Steeringhttp://en.wikipedia.org/wiki/Rack_railwayhttp://en.wikipedia.org/wiki/Rack_railwayhttp://en.wikipedia.org/wiki/Axis


14/20

Sun and planet gearing was a method of convertingreciprocal motion into rotary motion insteam engines. It played an important role in theIndustrial Revolution. The Sun is yellow, the

planet red, the reciprocatingcrankis blue, theflywheel is green and the driveshaftis grey.

Harmonic drive

A harmonic drive is a specializedproprietary gearing mechanism.
http://en.wikipedia.org/w/index.php?title=Reciprocal_motion&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Reciprocal_motion&action=edit&redlink=1http://en.wikipedia.org/wiki/Rotary_motionhttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Industrial_Revolutionhttp://en.wikipedia.org/wiki/Industrial_Revolutionhttp://en.wikipedia.org/wiki/Crankhttp://en.wikipedia.org/wiki/Crankhttp://en.wikipedia.org/wiki/Crankhttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Driveshafthttp://en.wikipedia.org/wiki/Driveshafthttp://en.wikipedia.org/wiki/Proprietaryhttp://en.wikipedia.org/wiki/File:Harmonic_drive_animation.gifhttp://en.wikipedia.org/wiki/File:Sun_and_planet_gears.gifhttp://en.wikipedia.org/w/index.php?title=Reciprocal_motion&action=edit&redlink=1http://en.wikipedia.org/wiki/Rotary_motionhttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Industrial_Revolutionhttp://en.wikipedia.org/wiki/Crankhttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Driveshafthttp://en.wikipedia.org/wiki/Proprietary


15/20

APPLICATIONS OF GEARS IN AUTOMOBILES

Gears are now used for a wide range of industrial applications. There are gears weighing from

15grams to 15 tons. Lots of industries use gears for transmitting power or rotational force from

one component to another. Gears have varied application starting from textile looms to aviation

industries. Undoubtedly the demand for gears in industries is estimated at a whopping 125 billiondollars worldwide.Cement plants use girth gears for crushing raw materials. These girth gears

have high strength and highly durable that they can be used in any operating environment. Forrotating equipments in the cement industry power transmission is essential and that is providedby various open gear drives. Other types of gears which are used in cement industries are

reduction gears, pinions, Sprockets, pinion shafts and helical gears.Coal plants also most

commonly use girth gears in their mining equipments. Heavy gearboxes are also being used inheavy machineries. There are two basic gearing principles which are:

- Craggy reliable gearing

- Worm gearing

These are used in many mining machines such special cutting machines, axle for forming tunnelsfor locomotives, etc. Gears are also used in compressors, cages, trolleys and diesel locomotives

that are used for coal mining.

Medical industry uses gears in a huge way. They are being used in the surgical tables, patient

beds, gear pumps for medical dosing applications, and also in medical diagnostic machine.

Micro assembly uses micro gears which enable us to have miniature components built with a

very compact size. Use of micro gears is really advantageous as they provide zero backlash, long


16/20


17/20

Automobile Differential Complete Schematic

Without the "square" set of four gears in the middle of the above diagram which yields to thefigure below, both wheels turn at the same angular velocity. This leads to problems when the car

negotiates a turn.

Automobile Wheel Drive without Differential

Now imagine the differential "square" alone, as illustrated in the following figure. It should be

apparent that turning one wheel results in the opposite wheel turning in the opposite direction at

the same rate.

Automobile Differential Alone

This is how the automobile differential works. It only comes into play when one wheel needs to

rotate differentially with respect to its counterpart. When the car is moving in a straight line, thedifferential gears do not rotate with respect to their axes. When the car negotiates a turn,

however, the differential allows the two wheels to rotate differentially with respect to each other.

One problem with an automotive differential is that if one wheel is held stationary, the

counterpart wheel turns at twice its normal speed as can be seen by examining the completescheme of automobile differential. This can be problematic when one wheel does not have

enough traction, such as when it is in snow or mud. The wheel without traction will spin without
http://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#TurningCarhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#TurningCarhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#TurningCarhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#AutomobileDifferentialhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#AutomobileDifferentialhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#AutomobileDifferentialhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#TurningCarhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#TurningCarhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#AutomobileDifferentialhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm#AutomobileDifferential


18/20

providing traction and the opposite wheel will stay still so that the car does not move. This is the

reason for a device known as a "limited slip differential" or "traction control".

Differential gear train on a turning car

The gear train in an automobile differential is a common application of gears, but oftenmisunderstood by the lay public. Here we present a simplified explanation of how and why an

automobile differential works.

The car is turning about a circle with nominal radius rn. (For this discussion, we assume that the

axis of the wheel axle for the driven (rear) wheels passes through the turn circle center. This istypically true only for a fairly large radius of turn.)

The outer wheel traverses an arc with radius ro and the inner wheel traverses an arc with radius ri.

As illustrated, the lengths of the arcs traversed are so, sn, and si. The outer arc so is obviouslylarger than the inner arc si for a given traversed angle theta. Some way of ensuring that the outer

wheel is able to turn slightly faster than the inner wheel must be ensured in order to prevent

binding and slippage of the tires on the road. For non-driven wheels which simply rotate freelyindependently of other machinery, this is not a problem. Driven wheels connected to the engine

via the driveshaft, however, must both be turned by gearing and this gear train must allow for

differential movement of the left wheel with respect to the right wheel. This is a difficult

problem since for every turning circle the differential rotation of the left and right wheels isdifferent. Fortunately, the automobile differential solves this problem with only one transmission

and one drive shaft for both driven wheels.


19/20

Gear model in modern physics

Modern physics adopted the gear model in different ways. In nineteenth centuryJames Clerk

Maxwell developed a model of electromagnetism in which magnetic field lines were rotating

tubes of incompressible fluid. Maxwell used gear wheel and called it idle wheel to explain theelectrical current as a rotation of particles in opposite direction to that of the rotating field lines.

A new consideration of gear in quantum physicsis regarded as a quantum gears. A group of

gears can serve as a model for several different systems such as an artificially constructed

nanomechanical device or a group of ring molecules.
http://en.wikipedia.org/wiki/Modern_physicshttp://en.wikipedia.org/wiki/James_Clerk_Maxwellhttp://en.wikipedia.org/wiki/James_Clerk_Maxwellhttp://en.wikipedia.org/wiki/James_Clerk_Maxwellhttp://en.wikipedia.org/wiki/Quantum_physicshttp://en.wikipedia.org/wiki/Quantum_physicshttp://en.wikipedia.org/wiki/Modern_physicshttp://en.wikipedia.org/wiki/James_Clerk_Maxwellhttp://en.wikipedia.org/wiki/James_Clerk_Maxwellhttp://en.wikipedia.org/wiki/Quantum_physics


20/20

BIBLIOGRAPHY

www.articlesbase.com/automotive-articles/applications-of-gears-

2028719.html

www.efunda.com/designstandards/gears/gears_auto_diff.cfm

Wikipedia, the free encyclopedia
http://www.articlesbase.com/automotive-articles/applications-of-gears-2028719.htmlhttp://www.articlesbase.com/automotive-articles/applications-of-gears-2028719.htmlhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfmhttp://www.articlesbase.com/automotive-articles/applications-of-gears-2028719.htmlhttp://www.articlesbase.com/automotive-articles/applications-of-gears-2028719.htmlhttp://www.efunda.com/designstandards/gears/gears_auto_diff.cfm

termpaper mec101

Documents