BE in Mechanical
Engineering has a subject called ‘Theory Of Machine’. In that subject we are
required to read various mechanisms about how machine and other things work.
The notable mechanisms are Four bar mechanism, Slider crank, belt and rope
drive mechanism and gear mechanism. We
are required to a mini project for the internal assessment. We choose to
develop a differential mechanism to show exactly how the differential in
automobiles works.
In automobiles and
other wheeled vehicles, a differential is the usual way to allow the driving
roadwheels to rotate at different speeds. This is necessary when the vehicle
turns, making the wheel that is travelling around the outside of the turning
curve roll farther and faster than the other. The engine is connected to the
shaft rotating at angular velocity . The driving wheels are connected to the
other two shafts, and and are equal. If the engine is running at a
constant speed, the rotational speed of each driving wheel can vary, but the
sum (or average) of the two wheels' speeds can not change. An increase in the
speed of one wheel must be balanced by an equal decrease in the speed of the
other. (If one wheel is rotating backward, which is possible in very tight
turns, its speed should be counted as negative.)
 |
| Differential gear |
It may seem illogical
that the speed of one input shaft can determine the speeds of two output
shafts, which are allowed to vary. Logically, the number of inputs should be at
least as great as the number of outputs. However, the system has another
constraint. Under normal conditions (i.e. only small tyre slip), the ratio of
the speeds of the two driving wheels equals the ratio of the radii of the paths
around which the two wheels are rolling, which is determined by the track-width
of the vehicle (the distance between the driving wheels) and the radius of the
turn. Thus the system does not have one input and two independent outputs. It
has two inputs and two outputs.
Here is how differential mechanism was developed and works.
I will keep updating the blog as my project work continues.
Sadly, the end semester came a bit quicker and we could not complete the project. However a little design was made.
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