pulley-block
Definition
Noun: A pulley-block is a simple machine consisting of a wheel (or sheave) with a grooved rim, mounted in a frame or block. A rope, cable, or belt runs in the groove, allowing the device to change the direction of an applied force or to provide a mechanical advantage when lifting or moving loads.
Usage
The term "pulley-block" refers specifically to the assembled unit containing the sheave(s) and its housing. It is a core component in pulley systems used for lifting, rigging, and transmitting power. - It is used to redirect a pulling force to a more convenient direction. - It is used in systems with multiple blocks to create a mechanical advantage, making it easier to lift heavy objects.
Examples
- The sailors used a pulley-block to hoist the sail efficiently.
- A system of pulley-blocks significantly reduced the effort needed to lift the engine from the car.
- The crane's mechanism relies on a series of heavy-duty pulley-blocks.
Advanced Usage
- Fixed Pulley-Block: A block that is attached to a structure. It changes the direction of the force but does not provide a mechanical advantage in terms of reducing the required force.
- Movable Pulley-Block: A block that moves with the load. When used in conjunction with a fixed block, it provides a mechanical advantage, reducing the force needed to lift the load.
- Compound Pulley System: A setup using multiple pulley-blocks (both fixed and movable) to create a high mechanical advantage, often used in cranes and hoists.
Variants and Related Words
- Pulley: A more common general term for the simple machine. "Pulley-block" often implies the complete, framed assembly.
- Sheave (noun): The grooved wheel within a pulley-block.
- Block and Tackle: A system of two or more pulley-blocks with a rope threaded through them to provide a substantial mechanical advantage.
Synonyms
- Block (in nautical or rigging contexts)
- Sheave block
Related Phrases
- To reeve a block: The action of threading a rope through a pulley-block.
- Snatch block: A type of pulley-block with a side plate that opens, allowing a rope to be inserted without threading it through from the end.
Noun
-
a simple machine consisting of a wheel with a groove in which a rope can run to change the direction or point of application of a force applied to the rope
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