Trucker's hitch advantage would be only 2:1. However in the common use of the trucker's hitch, a static hook, ring, or rail, serves as the lower pulley, and the rope across the top of the load is the portion being tensioned. Thus, the standing part of the rope is represented by the top anchor point in the diagram, and the theoretical ratio is indeed 3:1 when the working end is tensioned. That is, in a frictionless system, every unit of force exerted on the working end would produce 3 units in the standing part of the rope over the load. In the
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