Mech 203 Term Project Automobile Differential and Transmission Hakan Uzuner Ümmü Koç Ömer Fidan

Mech 203 Term Project Automobile Differential and

Transmission

Hakan Uzuner Ümmü Koç

Ömer Fidan

What is a differential?

Differential is a device capable of transmitting torque and rotation through three shafts, almost always used in one of two ways. In one of these, it receives one input and provides two outputs; this is found in most automobiles. In an automobile and other wheeled vehicles, the differential allows each of the driving wheels to rotate at different speeds, while supplying equal torque to each of them.

Purpose of a differential

The differential is found on all modern cars and trucks, and also in many all-wheel-drive vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels.

Differential Gear Train on a Turning Car


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 obviously larger 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.


Fortunately, the automobile differential solves this problem with only one transmission and one drive shaft for both driven wheels.


Since s=r(THETA), the length of the arc traversed for a given theta is proportional to the radius. Since ro is greater than rn by the same amount that ri is less than rn, the right wheel center must travel further than the car center by the same amount that the left wheel center must travel less further than the car center. As its name implies, a differential allows the left and right drive wheels to turn differentially with respect to each other. As can be seen by turning the drive wheels of a car on a mechanic's lift, turning one drive wheel results in the opposite wheel turning at the same rate in the opposite direction.

Automobile Differential Animation

http://auto.howstuffworks.com/differential2.htm

Parts of a differential

Differential

Automobile Differential in Unigraphics

Before we started our project, we researched the dimensions and overall shape of a differential system on internet and by visiting a car mechanic shop. After we acquired the necessary data, we started to construct our differential system by using Unigraphics. We reduced and normalized the dimensions that we collected for easier application to unigraphics.

Automobile Differential in Unigraphics

We scaled and normalized the dimensions we have gathered for easier drawing experience in Unigraphics.

Autmobile Differential in Unigraphics

Our differential system consisted of eight unique parts. Six of these were used to construct the differential. These included crown gear, sungear, planet pinion, drive shaft and half shafts, which connect to the wheels. Two remaining parts made up our wheels.



Automobile Transmission

Using the principle of mechanical advantage, transmissions provide a speed-torque conversion (commonly known as "gear reduction" or "speed reduction") from a higher speed motor to a slower but more forceful output or vice-versa.

Autmobile Transmission

Most modern gearboxes either reduce an unsuitable high speed and low torque of the prime mover output shaft to a more stable lower speed with higher torque, or do the opposite and provide a mechanical advantage (i.e increase in torque) to allow higher forces to be generated.

Autmobile Transmission

Manual transmission come in two basic types:

Sliding-mesh Constant-mesh


Sliding-mesh or unsynchronized / non-synchronous system, where straight-cut spur gear sets are spinning freely, and must be synchronized by the operator matching engine revs to road speed, to avoid noisy and damaging "gear clash"


Constant-mesh gearboxes which can include non-synchronised, or synchronized/synchromesh systems, where diagonal cut helical (and sometimes double-helical) gear sets are constantly "meshed" together, and a dog clutch is used for changing gears. On synchromesh boxes, friction cones or "synchro-rings" are used in addition to the dog clutch.

Automobile transmission

Automobile transmission in Unigraphics

The challenging part of designing a transmission in unigraphics was the amount of gears we had to draw. Gear drawing is hard due to the fact that each gear has to be perfect since they have to fit with the adjacent gears. We used the dimensions acquired from machine shops and internet to design an accurate transmission.


We designed fifteen gears for our trasmission (5 gears and reverse). We also included the synchronizers between the gears.







Documents

Mech 203 Term Project Automobile Differential and Transmission Hakan Uzuner Ümmü Koç Ömer Fidan