What size sheave is required for a 1/2" rope?

The correct sheave size required for a 1/2" rope is important for ensuring that the rope can operate effectively and safely within the system. The general rule of thumb in elevator practice is that the diameter of the sheave should be at least 40 times the diameter of the rope. This guideline helps to prevent excessive wear on the rope and contributes to proper grip and performance.

In this case, for a 1/2" rope, the minimum sheave diameter needed would be 20 inches. While sheaves larger than the minimum can also be used, the specified choice of 20 inches aligns with this practical requirement to maintain appropriate performance and longevity of the rope as it changes direction over the sheave.

Choosing a smaller size would lead to increased stress and strain on the rope, potentially causing premature failure or unsafe operating conditions. Hence, the selection of a 20" sheave is optimal, ensuring compatibility with a 1/2" rope under typical usage conditions.