Did you ever think how the wheels of your car initiated to move ahead. The rotational force is passed from the transmission to the differential. The drive-shaft also known as a propeller shaft or cardan shaft is a device that transfers rotational force from the transmission system to the differential. Technically, a drive-shaft transfers torque and rotation to parts of the vehicle that are far from the transmission system. In automobiles, it is a longitudinal shaft from an engine/transmission to the other end of the vehicle before it goes to the wheels. Physically, it is tubular in design, with an outside metal housing that protects an interior metal cylinder.
Parts of a differential:
Flange: The flange is a collar like structure that fastens the drive-shaft to the pinion gear.
Pinion gear: This is just a normal gear and rides on the larger ring gear at a 90 degree angle.
Side gears: Side gears receive the rotation directly from the ring gear and transfer it to the axle.
Ring Gear: The biggest gear in the differential. This is the gear that receives the rotation from the drive-shaft.
Left and right axle shaft: Axle shafts on both the sides of the vehicle.
Spider Gears: Spider gears hold both the axles intact and allow the two axles to rotate at two different speeds.
Why is a differential needed?
The need for a differential arises due to a single, simple reason. While the vehicle turns towards the right or left, the wheels don’t rotate in the same speed. While taking a turn, the distance traveled by the front wheels is always a little more than the rear wheels. Since distance is directly proportional to the speed, the wheels spin at different speeds.
Now, if all the wheels had been fixed in order to spin at the same speed, at turns, the slow-spinning wheels have to drag on the ground, since their necessity to undergo spinning is less. If the vehicle is making a right turn, the order of speeds in each wheel is Front Left>Front Right>Rear Left>Rear Right. In case of the absence of differentials, in hard surfaces such as tar, the drag faced by the wheel that undergoes less spin is more intense. This induces wear and tear on the tire and driving on such conditions is also difficult.
The drive-shaft carries the rotating motion from the engine crankshaft to the differential. At the differential, the Ring gear along with the side gear and pinion gear breaks the flow of rotational motion in between so that, the wheels can rotate at different speeds while the differential receives a single speed of rotation.