What happens to the allowable line pull as the number of rope layers on a drum increases?

As the number of rope layers on a drum increases, the allowable line pull decreases. This relationship is primarily due to the mechanics involved in how rope is wound and the friction encountered as the line pulls from the drum.

When additional layers of rope are added to the drum, the effective diameter at which the rope pulls increases. As the number of layers increases, the friction between the layers of rope and the drum also increases. This extra friction makes it more difficult to pull the line and decreases the overall efficiency of the pull.

Consequently, the structural limits of the rope and the drum itself mean that the line can only sustain a certain amount of load safely before the risk of failure or slippage occurs. Thus, with more layers, the tension and pressure on the rope increase, leading to a reduction in the allowable line pull.

This understanding is essential for operators to ensure safe lifting practices and to maximize the performance of the crane without exceeding the limits set by the manufacturer or safety standards.