wheel and axle


wheel and axle
a simple machine consisting, in its typical form, of a cylindrical drum to which a wheel concentric with the drum is firmly fastened: ropes are so applied that as one unwinds from the wheel, another rope is wound on to the drum.
[1765-75]

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 basic machine component for amplifying force. In its earliest form it was probably used for raising weights or water buckets from wells. Its principle of operation is demonstrated by the large and small gears attached to the same shaft, as shown at A in the illustration—>. The tendency of a force F applied at the radius R on the large gear to turn the shaft is sufficient to overcome the larger force W at the radius r on the small gear. The force amplification, or mechanical advantage, is equal to the ratio of the two forces (W:F) and also equal to the ratio of the radii of the two gears (R:r).

 For raising weights the wheel and axle has large- and small-diameter drums with ropes wrapped around them in place of the gears. The weight being lifted is attached to the rope on the small drum, and the operator pulls the rope on the large drum. In this arrangement the mechanical advantage is the radius of the large drum divided by the radius of the small drum. An increase in the mechanical advantage can be obtained by using a small drum with two diameters, r1 and r2, and a pulley block, P, as shown in sketch B in the illustration—>. When lifting a weight, the rope winds on the drum D and off the drum d.

      A measure of the force amplification available with the system is the velocity ratio, or the ratio of the velocity (VF) with which the operator pulls the rope at F to the velocity at which the weight W is raised (VW). This ratio is equal to twice the radius of the large drum divided by the difference in the radii of drums D and d. Expressed mathematically, the equation is VF/VW = 2R/(r2 - r1). The actual mechanical advantage W/F is less than this velocity ratio, depending on friction. A very large mechanical advantage may be obtained with this arrangement by making the pulleys D and d of nearly equal radius. See also block and tackle.

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Universalium. 2010.

Look at other dictionaries:

  • Wheel and axle — Wheel Wheel (hw[=e]l), n. [OE. wheel, hweol, AS. hwe[ o]l, hweogul, hweowol; akin to D. wiel, Icel. hv[=e]l, Gr. ky klos, Skr. cakra; cf. Icel. hj[=o]l, Dan. hiul, Sw. hjul. [root]218. Cf. {Cycle}, {Cyclopedia}.] [1913 Webster] 1. A circular… …   The Collaborative International Dictionary of English

  • wheel and axle — n. a larger wheel or pulley that is fixed to a shaft, a smaller wheel or pulley, or a drum, to increase mechanical advantage or speed: the wheels are often grooved and operated like pulleys …   English World dictionary

  • Wheel and axle — The wheel and axle is a simple machine. The traditional form as recognised in 19th century textbooks is as shown in the image. This also shows the most widely recognised application, ie lifting water from a well. The form consists of a wheel that …   Wikipedia

  • wheel and axle — noun a simple machine consisting of a wheel (or similar lever) that turns an axle around which a cord is wound; its mechanical advantage is the ratio of the diameters of the wheel and axle …   Wiktionary

  • wheel and axle — wheel′ and ax′le n. mac a simple machine consisting typically of a cylindrical drum to which a concentric wheel is firmly fastened: ropes are so applied that as one rope unwinds from the wheel, another is wound onto the drum • Etymology: 1765–75 …   From formal English to slang

  • wheel and axle — noun Date: 1759 a mechanical device consisting of a grooved wheel turned by a cord or chain with a rigidly attached axle (as for winding up a weight) together with the supporting standards …   New Collegiate Dictionary

  • wheel and axle — simple machine comprised of a wheel attached concentrically to a drum so that a rope will wind and unwind alternately from the wheel to the drum creating mechanical advantage …   English contemporary dictionary

  • wheel and axle — noun a device (one of the so called simple machines) consisting, in its typical form, of a cylindrical drum to which a wheel concentric with the drum is firmly fastened. Ropes are so applied that as one unwinds from the wheel the other is wound… …   Australian English dictionary

  • wheel and axle — noun hoist so arranged that a rope unwinding from a wheel is wound onto a cylindrical drum or shaft coaxial with the wheel • Hypernyms: ↑hoist …   Useful english dictionary

  • crown wheel and pinion — A pair of gears in the final drive of a vehicle, always found in the back axle of a rear wheel drive layout where the pinion is on the end of the propeller shaft driving the crown wheel mounted on the differential at right angles to it, and also… …   Dictionary of automotive terms


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