MDC Differential-Crownwheel and Pinion



The Differential-Crownwheel and Pinion, "MDC" has been designed to demonstrate the action of the elements of a differential: the crownwheel and the pinion.

See general description

General Description

The Differential-Crownwheel and Pinion, "MDC", designed by EDIBON, simulates a differential mechanism. The function of the differential mechanism is to enable the drive wheels rotate at different speeds, regardless of whether they are the front or rear wheels.

When the vehicle is travelling in a straight line, the differential must behave as if it were rigid and make both wheels rotate at the same speed. It means that in this situation the sun gears do not spin around their own axis, in other words, they act as wedges to transmit the motion of the crown.

Therefore, the differential allows to provide the torque to either both wheels or only one wheel. When both wheels have the same load the differential supplies the same torque to both of them, but when one of them supports a greater load than the other, then motion is distributed uniformly.

This unit consists of:

  • Input pinion.
  • Crown-wheel.
  • Three gears, named sun gears.
  • Two gears coupled to the shafts of the wheels, named planetary gears.
  • Three pulleys with protractor.

The input pinion transfers the power to the crown. That motion of the crown drives the sun gears and they, rotating together with the crownwheel, transfer the power to the planetary gears. The planetary gears at the same time transfer the power to the output shafts, allowing them to rotate at the same or different speed.

Exercises and guided practices


  1. Determination of the input and output speed ratio and the torque distribution.
  2. Study of the efficiency.
  3. Study of the use of a differential as a simple transmission system.
  4. Visualization and demonstration of the behaviour of a differential when used as a means to provide a drive.
  5. Verification of the gear ratio.