What is the term for a wheel with a concave edge for supporting a moving rope that is changing direction?

The term for a wheel with a concave edge that supports a moving rope and assists in changing its direction is "sheave." Sheaves are integral components in various mechanical systems, particularly in lifting and material handling applications.

The design of a sheave allows the rope to fit securely within the concave groove, minimizing wear and enhancing efficiency as the rope moves over the wheel. This curvature not only aids in the smooth movement of the rope but also helps prevent slippage, ensuring that the force is effectively transmitted through the system.

In contrast, a pulley generally refers to the entire assembly that consists of the sheave and any surrounding hardware that facilitates the lifting of loads. A spindle is typically a rotating shaft that supports rotating components, while an axle is a central shaft for rotating wheels or gears. These definitions highlight why "sheave" is the most accurate terminology for a wheel that specifically interacts with a rope in the manner described.