What happens to the line pull as wire rope spools onto a hoist drum and the layers on the drum increase?

As wire rope spools onto a hoist drum and the number of layers on the drum increases, the line pull decreases. This phenomenon occurs due to the mechanical advantage gained by the way the rope is wrapped around the drum.

When the wire rope is initially wound around the drum, it is at a smaller diameter, and as additional layers are added, the effective diameter of the drum increases. The line pull, which refers to the tension in the rope, is affected by the increase in the drum diameter because the load is being distributed over a larger drum surface area.

Additionally, as more layers are added, the friction generated by the windings of the wire rope against each other and against the drum increases. This friction impedes the lifting capability of the crane, leading to a reduction in effective line pull with each subsequent layer.

This principle is essential for crane operators and maintenance personnel to understand, as it directly relates to the performance and safety of lifting operations.