Pulley

**Block and Tackle Pulley Systems**:
– A block consists of pulleys that rotate independently.
– Two blocks with a rope form a block and tackle.
– Mechanical advantage of block and tackle equals sections of supporting rope.
– Different types of block and tackle have varying mechanical advantages.
– Compound pulley systems provide mechanical advantage for lifting loads.
– Rope and pulley systems reduce input force to lift heavy loads.
– Compound pulleys increase mechanical advantage in lifting operations.

**Rope and Pulley Systems**:
– A block and tackle system uses a continuous rope to lift loads.
– Mechanical advantage of a rope and pulley system is determined by the number of supporting rope parts.
– Different types of tackles, like gun tackle and double tackle, vary in mechanical advantage.
– Rope and pulley systems reduce input force to lift heavy loads.
– Compound pulleys increase mechanical advantage in lifting operations.

**Method of Operation and Types of Pulley Systems**:
– Pulley systems operate assuming weightless pulleys and no energy loss due to friction.
– Different types of pulley systems include fixed, movable, and compound pulleys.
– Mechanical advantage is gained by combining fixed and movable pulleys.
– Rove to advantage pulley systems increase mechanical advantage.
– Free body diagrams help analyze the mechanical advantage of pulley systems.
– Pulley systems allow for the change of direction without energy dissipation.

**Belt and Pulley Systems**:
– Belt and pulley systems use two or more pulleys connected by a belt.
– Mechanical power, torque, and speed are transmitted through belt and pulley systems.
– Differing diameters of pulleys provide mechanical advantage.
– Belt drives are similar to chain drives but with smooth sheaves.
– Mechanical advantage in belt and pulley systems depends on pulley diameters.
– Drum-style pulleys are often slightly convex to center flat belts.
– Agricultural tractors built up to the early 1950s commonly had a flat belt pulley.

**Friction in Belts and Pulleys**:
– Peculiar angles can lead to bad belt tracking and slipping off the pulley.
– Low belt-tension environments can cause unnecessary slippage and extra wear.
– Pulleys are sometimes lagged to improve friction between the belt and the pulley.
– Lagging extends the life of the shell by providing a replaceable wearing surface.
– Drive pulleys are often rubber lagged for improved friction.