What is Weston's Differential pulley ? Find the mechanical advantage of this pulley . Explain in great details . No links .
Weston's differential pulley, also called sometimes chain hoist or colloquially "chain fall", is used to manually lift very heavy objects like engines of car or any other motor. 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 the same place (and not lower under the force of gravity) until the chain is pulled.
The force needed to lift a load is only a fraction of the load's weight. At the same time, the distance the load is lifted is smaller than the length of chain pulled by the same factor. This factor (the mechanical advantage MA) depends on the relative difference of the radii r and R of the connected pulleys: