block and tackle

block and tackleHalf the pull (p) is required to lift the weight (w) with a two-pulley block and tackle unit.

block and tackle

n. An apparatus of pulley blocks and ropes or cables used for hauling and hoisting heavy objects.

block and tackle

n (Mechanical Engineering) a hoisting device in which a rope or chain is passed around a pair of blocks containing one or more pulleys. The upper block is secured overhead and the lower block supports the load, the effort being applied to the free end of the rope or chain

block′ and tack′le

n. the ropes or chains and blocks used in a hoisting tackle. [1830–40]

block and tackle

(blŏk) A device consisting of a fixed pulley and a movable one, in which the rope attached to the load is passed over the fixed pulley, around the movable pulley, then back around the fixed one. Each pulley can have multiple grooves or wheels for the rope to pass over additional times. The more times the rope is passed around the two pulleys, the less effort is needed to raise a load.

Thesaurus

Noun

block and tackle - pulley blocks with associated rope or cablehoist - lifting device for raising heavy or cumbersome objectspulley, pulley block, pulley-block, block - 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

Translations

contrastoparancoplaccaggio

block and tackle

block and tackle:

see pulleypulley,
simple machine consisting of a wheel over which a rope, belt, chain, or cable runs.

A grooved pulley wheel like that used for ropes is called a sheave. A single sheave mounted in a block and fixed in place simply changes the direction of force exerted on the rope
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Block and Tackle

a load-lifting device that consists of pulleys mounted in fixed and moving blocks and rigged with a continuous cable. A block and tackle provides a mechanical advantage or an advantage in speed. It is usually part of the mechanism for raising and extending the booms of hoisting cranes and rigging equipment. However, a block and tackle can also be used independently for raising or lowering small loads, such as ship’s boats.

In a block and tackle that is used to provide a mechanical advantage, the load is suspended from the moving block, and the pull is exerted on the part of the cable that runs from the last of the pulleys through which the cable is reeved. If frictional losses are ignored, the tensile force that acts upon the cable can be defined as the quotient obtained when the weight of the load is divided by the number of parts of the cable that support the load.

Essentially the opposite arrangement is used with a block and tackle that functions to speed up the movement of a load. This means that the force, which is usually supplied by a hydraulic or pneumatic cylinder, is applied to the moving block and the load is suspended from the running part of the cable. The advantage in speed with such a block and tackle results from the increased hoist of the load; this hoist is equal to the product obtained by multiplying the piston stroke of the power cylinder by the number of parts of the cable.

I. G. GERTSKIS

Block and Tackle

a suspended device for lifting loads. A block and tackle may be operated manually or mechanically (either electrically or pneumatically), and it may be stationary or mobile. Mobile tackles are suspended from special carriages that move on single-rail tracks.

Manually operated tackles have a housing containing the block and a hook from which the load is suspended. The upper block has a worm or gear transmission and is operated manually by means of an endless chain. A roller or welded-link chain goes around the drive sprocket (or pulley) and the moving sprocket (or pulley) of the lower block. The upper block is equipped with a brake to prevent accidental lowering of the load. Lifting capacities range from 0.25 to 10 tons, and loads may be raised 3 to 12 m.

An electrically driven block and tackle consists of a winch with a reduction gear, an electric motor, a drum or sprocket, a brake, and a hook. Lifting capacities range from 0.25 to 5 tons, and loads may be raised 3 to 18 m. The hoisting speed is 20 m/min when the hoist is operated from a control console on the floor and up to 360 m/min when it is controlled from a cab traveling together with the tackle. Current is supplied through trolley conductors or flexible cables.

Pneumatically driven tackles are used where there is a danger of fire. Compressed air is usually supplied from a compressor station or from gas cylinders delivered to the work location. The pneumatic drive ensures a smooth, stepless regulation of the hoisting speed.

Tackles are used as self-containing hoisting devices in industrial shops, storage areas, and repair shops and aboard ships. They are also used as hoists in single-rail bridge cranes, stationary and mobile wall-bracket cantilever cranes, and in single-rail hoist carriages.

REFERENCE

Gruzopod” emnye mashiny. Moscow, 1973.

T. A. NIKOL’SKAIA

block and tackle

[‚bläk ən ′tak·əl] (mechanical engineering) Combination of a rope or other flexible material and independently rotating frictionless pulleys. Also known as block and fall.

block and tackle

A pulley block, 6 together with rope or cable, used to raise or shift a load.

block and tackle

a hoisting device in which a rope or chain is passed around a pair of blocks containing one or more pulleys. The upper block is secured overhead and the lower block supports the load, the effort being applied to the free end of the rope or chain

block and tackle

block and tackle

block and tackle

block′ and tack′le

block and tackle

block and tackle

block and tackle:

Block and Tackle

Block and Tackle

REFERENCE

block and tackle

block and tackle

block and tackle

Block and Tackle

block and tackle

Words related to block and tackle

noun pulley blocks with associated rope or cable

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