Differential pulley were. Next, the downward force acting on the lower pulley equal the upward forces acting on it, so Additionally, there is no net torque or moment around the compound pulley, so the clockwise torque is equal to the anticlockwise torque: Substituting "F" and "F" from the above equations, Rearranging gives As "F" = , Finally, the mechanical advantage, = or . Differential pulley 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
Block and tackle output force), formula_5 is the ideal mechanical advantage of the system (which is the same as the number of segments of line extending from the moving block), and formula_6 is the mechanical efficiency of the system (equal to one for an ideal frictionless system; a fraction less than one for real-world systems with energy losses due to friction and other causes). If formula_7 is the number of sheaves in the purchase, and there is a roughly formula_8% loss of efficiency at each sheave due to friction, then: This approximation is more accurate for smaller values of formula_7 and formula_8. A