Purchase includes free access to book updates online and a free trial membership in the publisher's book club where you can select from more than a million books without charge. Chapters: Simple Machine, Lever, Inclined Plane, Pulley, Block and Tackle, Wedge, Wheel and Axle, Scrollerwheel, Relieving Tackle, Rolamite, Plunger, Screw, Differential Pulley, Compound Lever, Telescoping. Excerpt: A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. The block and tackle pulley was probably invented by Archimedes .Overview This block and tackle on a davit of the Mercator is used to help lower a boat.Various ways of rigging a tackle. All these are rove to disadvantage. Seamen aboard the now-defunct USNS Southern Cross freighter rigged this block and tackle to make heavy lifts during cargo operations.Although used in many situations, they are especially common on boats and sailing ships , where motorized aids are usually not available and the task must be performed manually.A block is a set of pulleys or "sheaves " all mounted on a single axle . When rope or line is run through a block or a series of blocks the whole assembly is called a tackle. Usually it is a compound machine.The most common arrangement of block and tackle is to have a block attached to a fixed position (the fixed or standing block), and another block left to move with the load being pulled or lifted (the moving block).The block and tackle pulley is actually a compound pulley.Mechanical advantage The mechanical advantage of a block and tackle is equal to the number of parts in the line that either attach to or run through the moving block, or the number of supporting ropes. For example, take a block and tackle with 2 sheaves on both the moving block and the fixed block. If the blocks are compared, one will have 4 lines running through its sheaves, and the other will have 4 lines running through its sheaves
Be the first to rate this product.