Block and tackle sheave to change the direction of the pulling line, which increases friction losses without improving the velocity ratio. Situations in which reeving to disadvantage may be more desirable include lifting from a fixed point overhead; the additional pulley allows pulling downwards instead of upwards so that the weight of the lifter can offset the weight of the load. The formula used to find the effort required to raise a given weight using a block and fall: where formula_3 is the force applied to the hauling part of the line (the input force), formula_4 is the weight of the load (the
Wire rope spooling technology its behaviour and affects lifespan. Fleet angle should be between 0.25° and 1.25°, depending on the rope construction. The fleet angle can be varied by moving the first sheave closer to or further away from the drum. If the sheave is too close to the drum, the fleet angle will be greater than 1.25°; if it is too far away, the fleet angle will be less than 0.25°. Sometimes it is not possible to achieve the optimum fleet angle. Where there is no space to rig a sheave the requisite distance from the drum, two additional spooling devices are available.