Pulley If there are "p" of these parts of the rope supporting the load "W," then a force balance on the moving block shows that the tension in each of the parts of the rope must be "W/p." This means the input force on the rope is "T"="W/p." Thus, the block and tackle reduces the input force by the factor "p." The simplest theory of operation for a pulley system assumes that the pulleys and lines are weightless, and that there is no energy loss due to friction. It is also assumed that the lines do not stretch. In equilibrium, the
Fly system hoist (of an automated line set). Rope line (hemp) head blocks are typically upright blocks that mount to the rope line head block well channels at the grid level. In a counterweight rigging system the head block sheave is grooved for both the steel cable lift lines and an operating line, with the groove for the operating line provided at the middle of the multi-grooved sheave, between the lift lines. Counterweight head blocks mount atop or at the underside of the head block beam, depending on the beam's vertical position. The diameter of a head block sheave used for galvanized