Topic summary
Drive pulley
Extracted from the Wikipedia article Pulley.
Belt-and-pulley systems
With belts and pulleys, friction is one of the most important factors. Some uses for belts and pulleys involve peculiar angles (leading to bad belt tracking and possibly slipping the belt off the pulley) or low–belt-tension environments, causing unnecessary slippage of the belt and hence extra wear to the belt. To solve this, pulleys are sometimes lagged. Lagging is the term used to describe a coating, cover or wearing surface with various textured patterns applied to pulley shells, or the application thereof. Lagging is often used to extend the life of the shell by providing a replaceable outer layer or to improve the friction between the belt and the pulley. Notably, drive pulleys are often rubber-lagged (coated with a rubber friction layer) for exactly this reason. Applying powdered rosin to the belt may increase the friction temporarily but may shorten the life of the belt.