Differential pulley
![Example of a differential pulley](/Images/godic/202501/09/Chain_hoist.svg4120.png")
![Comparison of a differential pulley (left) and a differential windlass or Chinese windlass (right). The rope of the windlass is depicted as spirals for clarity, but is more likely helices with axes perpendicular to the image.](/Images/godic/202501/09/Comparison_differential_pulley_windlass.svg4120.png")
A differential pulley, also called "Weston differential pulley", sometimes "chain hoist" or colloquially "chain fall", is used to manually lift very heavy objects like car engines. It is operated by pulling upon the slack section of a continuous chain that wraps around pulleys. The relative size of two connected pulleys determines the maximum weight that can be lifted by hand. The load will remain in place (and not lower under the force of gravity) until the chain is pulled.