This wall-mounted apparatus comprises of Ø250mm wheel that is attached to a differential axle assembly of Ø100mm (major axle) and Ø50mm (minor axle). The whole axle assembly is locked to a shaft that is mounted on bearing with the wall mounting plate. A compound pulley is formed by fixing these three pulleys together. A single cord is wound around the wheel a number of times before hanging vertically and ending in a loop for the load hanger.

A second cord is wound on both the major and minor axles. The cord is wound in opposing directions onto each axle, and this direction can be changed for different parts of the experiments. A special hanger for effort is mounted to the cord of the axles that allows vertical suspension whilst the axles rotate.