Gin pole until the topmost portion of the tower is completed. Gin poles are mounted on flatbed trucks as a primitive form of mobile crane, used for lifting and relocating loads, and salvage operations in lieu of a more sophisticated wrecker. Gin pole A gin pole, derived from gyn, is a supported pole that uses a pulley or block and tackle on its upper end to lift loads. The lower end is braced or set in a shallow hole and positioned so the upper end lies above the object to be lifted. The pole (also known as a "mast", "boom", or "spar")
Block and tackle each of the parts of the rope must be "F/n." This means the input force on the rope is "F"="F/n." Thus, the block and tackle reduces the input force by the factor "n." Ideal mechanical advantage correlates directly with velocity ratio. The velocity ratio of a tackle is the ratio between the velocity of the hauling line to that of the hauled load. A line with a mechanical advantage of 4 has a velocity ratio of 4:1. In other words, to raise a load at 1 metre per second, the hauling part of the rope must be pulled at 4