A sheave is essentially a wheel with an open groove that a rope or cable is wrapped around so that it may revolve around the outside of the wheel. In this case, one end of the cable is attached to an item that needs to be moved, and the other end is attached to a stationary object, such as the base of a crane.
It is a grooved wheel that is used to guide and retain wire rope, and it has a number of uses. In order for the wire rope to move freely, the sheave spins on a bearing, hence reducing friction and wear on the rope while also providing for a more smooth crane operation.
What is a rooster sheave on a crane?
In most cases, it consists of a single sheave unit that connects to the tip of the beam and serves as a second hoisting line. This sheave is particularly useful on big lift cranes that have many sections of line running from the main boom tip.