The Busy Shore: The Block and Tackle System

The author explains how a block and tackle system multiplies human strength and illustrates a number of uses for them.



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The parts of a block and tackle system.
ILLUSTRATION: MOTHER EARTH NEWS STAFF
Adkins - busy shore - block and tackle 01
You're especially likely to see a block and tackles system wherever boats are used.
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When the GUN TACKLE is rove to advantage (when the pull is in the proper direction) its advantage is 3x; rove opposite, the mechanical advantage is 1.5x.
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A RUNNER yields a mechanical advantage of 2x when the pull is away from the weight; but toward the weight, a single block only changes the direction of the pull.
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Dividing a weight between two ropes assures that each bears only half the load.
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The fiddle block, a variation on the block and tackle concept that places one pulley above the other.
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A DOUBLE TACKLE is for heavy work, offering a mechanical advantage of 5x, but requiring much rope and a long haul.
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Like all moving machines, friction takes its due, and each sheave demands a part of the effort. Sailors figure that 5-8% is added for each sheave, and a formula estimating a somewhat greater loss is used by fishermen (Pull on the active tine = P; W = Weight lifted; F = number of falls, or lines, from the moving block.)
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A luff tackle with a tail sinnet instead of a hook is called a HANDY BILLY, and is used for many jobs aboard ship, especially for setting lines taut. The sinnet is half-hitched once or twice around the line to be set, then made fast with a Rolling Hitch.
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The LUFF TACKLE, with a mechanical advantage of 4x, is used a great deal aboard ship.
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The SPANISH BURTON is a specialized tackle for short hauls, used for bringing anchors, stores, and dories aboard.
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A patent come along can be very handy. A couple of folks can move damn near anything by applying and multiplying their strength cleverly... we are strong in our heads.
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Adkins - busy shore - anchor bends
Hook bends make a line fast to a block's hook. The BLOCKWALL HITCH is simple and secure under steady pull. An ANCHOR BEND is more secure for hoisting jerks. Because a single line might slip, a STROP is often spliced up for hoisting; both bights are slipped over the hook, or one is passed through the other and the single bight is secured to the hook with a CAT'S PAW.
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Adkins - busy shore - winch
Aboard ship, a winch is often the source for raw power. With a snatch block, the power can be transmitted and directed for almost any purpose. Sailors regularly run aground, and almost as regularly kedge themselves off with their own winches.
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Adkins - busy shore - making a block
 Gee whiz, but blocks are expensive; probably because they are marketed for construction companies and spiffy yachtsmen. You can make beautiful blocks in any case-rope-stropped blocks whose shells are shaped, drilled, and mortised from blocks of locust, elm, ash, madiera, ironwood, or lignum vitae. Sheaves, washers, pins, and thimbles can be had at a good chandlery. The block is stropped with a rope grommet made from a single ropestrand relaid into itself. It is forced around the shell, holding in the pivot, and seized tight with marline. H.G. Smith's The Arts of the Sailor gives the true 'gen on rope-stropped blocks and other watery marvels—fine book.
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A neglected labor-saver is the old-style barrel. Its subtle workings are no less stupendous and historically important than blocks & tackles. One man can move and direct huge loads by rolling it on its converse sides.
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Two sturdy spars lashed into a simple A-frame can be used to lift and move great weights. Vehicles bogged in mud can be lifted right out with a big A-frame.
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Boatyard workers are accustomed to moving 35 ton vessels with four jacks, some wooden rollers, and a winch. Moving smaller boats, a Johnson bar—a large pry-bar with wheels—is useful.
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