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arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. From a historical perspective, many of the first machines were the result of human efforts to improve war-making capabilities; the term engineer
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 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 passing over it. If the end of the rope that ordinarily would attach to the load is passed around a second, unfixed pulley and back to the fixed pulley, a load attached to the free pulley can be raised with half the effort, or with a mechanical advantage of 2. Thus arranged, the device is called a block and tackle. The number of pulley wheels mounted in the fixed and free blocks can be increased indefinitely to get a higher and higher mechanical advantage, the mechanical advantage equaling the number of strands running to the free pulley. Therefore if the rope is run over the first fixed pulley wheel, around the free pulley, over a second pulley wheel in the fixed block, and back to the free block, the mechanical advantage is 3. A 300-lb load can be raised by a pull of 100 lb on the free end of the rope. To raise the load 10 ft, however, the free end of the rope must be pulled 30 ft.

Disregarding friction, work output will always equal work input. If the action is reversed by attaching the load to the free end of the rope and pulling on the free block, the mechanical advantage becomes a mechanical disadvantage, but a speed advantage. A rope block and tackle is usually for hand operation. To lift larger loads by hand, a chain is substituted for the rope and the pulleys have grooves for gripping the links. A differential pulley consists of two pulleys of different radii connected and rotating as one on a common axle. The pulleys have their circumferences grooved and spiked so that a chain will run in them without slipping. Over the pulleys an endless chain is run, forming two hanging loops. In one loop is placed a movable block, whose pulley is shaped to take the chain. The load is attached to the movable block and is raised by pulling on the other loop of the chain.

Power-operated machinery usually has cables, as in vertical-lift drawbridges, power shovels, and cranes. Before the extensive use of electric motors, steam engines or water turbines often supplied the power for factory machinery. One engine or turbine might run a whole factory through a complicated system of shafts, pulleys, and belts. Pulleys for flat belts are crowned to keep the belt centered. Raised flanges will serve the same purpose, but they wear the edges of the belt. Drive pulleys for conveyor belts often have a covering, called lagging, to provide better grip. Individual electric motors usually provide drive by means of V belts, the pulleys having raised flanges to form slots that match the trapezoidal cross sections of the belts. Cone pulleys consist of a number of pulleys of varying diameters massed in the shape of a cone. They are used with belt drives for machines (e.g., lathes) requiring a variety of speeds.



a rotating part of a belt drive or a cable transmission, made in the form of a wheel around which a flexible link passes. Drive pulleys and driven pulleys, which transmit torque, are fastened to shafts by means of, for example, key or spline joints. Pulleys that do not transmit torque, such as idler and tension pulleys, turn freely on shafts or axles. Pulleys with grooved surfaces are sometimes called sheaves.

Pulleys are available in a wide variety of designs. Pulleys of small diameter are manufactured in one solid piece (Figure l,a). Pulleys of medium or large-diameter (Figure l,b) have a hub (1) and a rim (2) connected by a web (3) or by arms. Large pulleys are sometimes produced in two halves, which are bolted together. Pulleys may be made of cast iron, steel (Figure l,c), a light alloy, plastic, or—in some cases—wood.

Figure 1. Pulleys: (a) a one-piece pulley, (b) a pulley with a hub and rim, (c) a pressed-steel pulley, (d) a step pulley

Flat-belt pulleys (Figure 1,a) have a cylindrical or crowned peripheral surface to prevent the belt from being thrown off; flanges (4) are sometimes used for the same purpose. V-belt pulleys for single-belt or multiple-belt drives have grooves with a trapezoidal cross section (Figure l,b). Round-belt pulleys have a groove with a rounded bottom. Timing-belt pulleys have flanges and axial grooves for the teeth of the timing belt. Step pulleys (Figure 1,d) are used in drives in which the transmission ratio is adjusted by shifting the belt from one step to another. Doublecone pulleys in continuously variable transmissions with a wide V belt are produced with one or two springloaded movable cones; the displacement of one or both cones is forced.




(Russian, espander), a piece of athletic training equipment with springs or weights, used to create an additional load on specific muscle groups during various physical exercises, such as stretching and lifting weights. Both stationary and portable types are used.


(design engineering)
A wheel with a flat, round, or grooved rim that rotates on a shaft and carries a flat belt, V-belt, rope, or chain to transmit motion and energy.


1. A wheel having a grooved rim for carrying a rope or other line and turning in a frame; a pulley sheave.
2. A pulley block containing one or more pulley sheaves.


1. a wheel with a grooved rim in which a rope, chain, or belt can run in order to change the direction or point of application of a force applied to the rope, etc.
2. a number of such wheels pivoted in parallel in a block, used to raise heavy loads
3. a wheel with a flat, convex, or grooved rim mounted on a shaft and driven by or driving a belt passing around it
References in periodicals archive ?
Reduced down time on non-drive pulleys, where pulley change-out due to excessive wear is difficult.
Because the secondary pulley transmits torque through positive engagement, there is no possibility of slipping between chain and pulley and [F.
The power of the crankshaft is transferred from the drive pulley on the crankshaft to the driven pulley via the belt, and it is further transferred to the rear wheel after the speed is reduced in the reduction gear.
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teacher Pulley ' In Birmingham, 140 parents were fined in 2014-15 , a rise of 56 on the previous academic year.
The Watchmaker of Filigree Street is a remarkable debut," declared the Los Angeles Times, "and I look forward to seeing what Pulley does next.
The authors performed a comprehensive root cause failure analysis, beginning with a visual examination of the subject and exemplar vehicles, as well as macroscopic and microscopic inspection of the pulley.
The Martin Durt Dozer plow is designed to handle standard tail pulleys or wing pulleys on single-direction belts.
None of the studies required the students to design their own pulley systems and use them for balancing activities.
Like the VPlow HD, the Martin Durt DozerT Plow is designed to handle standard tail pulleys or wing pulleys on single-direction belts.
The diameter of the proximal pulley was set at 10 mm, which was the maximal diameter that would fit inside an anthropomorphic finger together with the finger frame.
Starting at PS58, it comes with everything you need to install it - wooden rails, two cast iron rack ends, a single pulley, double pulley, cleat hook and a 10m cotton durable rope.