Bosun’s Chair

Bosun's ChairThis exhibit demonstrates the mechanical advantage of rope and pulley systems with three chairs equipped with different arrangements of a fixed pulley and a movable pulley attached to the top of each chair. Visitors sit in each chair and hoist themselves up approximately 10 inches. The simplest pulley arrangement gives the visitor a 2:1 advantage to lift himself along with the 50 pound chair, so the effort required for lifting is close to the visitor’s weight. Another chair has a pulley arrangement with a mechanical advantage of 4:1 and the third chair is 6:1 for the easiest lifting effort.

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