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A worm gear, or worm wheel, is a type of gear that engages with a worm to greatly reduce rotational speed, or to allow higher torque to be transmitted. The image shows a section of a gear box with a bronze worm gear being driven by a worm. Image File history File links Download high resolution version (1746x1203, 289 KB) Photograph taken by Glenn McKechnie on 29th August 2005. ...
Image File history File links Download high resolution version (1746x1203, 289 KB) Photograph taken by Glenn McKechnie on 29th August 2005. ...
Spur gears found on a piece of farm equipment. ...
Revolutions per minute (abbreviated rpm, RPM, r/min, or min-1) is a unit of frequency, commonly used to measure rotational speed, in particular in the case of rotation around a fixed axis. ...
In physics, torque can be thought of informally as rotational force. Torque is commonly measured in units of newton metres; although, centiNewton Meters (cNm), Foot Pounds (Lb-Ft), Inch Pounds (Lb-In) and Inch Ounces (Oz-In) are also frequently used expressions of torque. ...
Explanation
A gearbox designed using a worm and worm-wheel will be considerably smaller than one made from plain spur gears and has its drive axes at 90° to each other. With a single start worm, for each 360° turn of the worm, the worm-gear advances only one tooth of the gear. Therefore, regardless of the worm's size (sensible engineering limits notwithstanding), the gear ratio is determined by the size of the worm gear:1. Given a single start worm, a 20 tooth worm gear will reduce the speed by the ratio of 20:1. A typical spur gear of 12 teeth (the smallest size permissible, (if designed to good engineering practices) would require a 240 tooth gear to achieve the same ratio of 20:1. Therefore, if the diametrical pitch (DP) of each gear was the same, then, in terms of the physical size of the 240 tooth gear to that of the 20 tooth gear, the worm arrangement is considerably smaller in volume. In mechanics, a transmission or gearbox is the gear and/or hydraulic system that transmits mechanical power from a prime mover (which can be an engine or electric motor), to some form of useful output device. ...
Spur gears found on a piece of farm equipment. ...
Image File history File links Doublebass_scroll. ...
Image File history File links Doublebass_scroll. ...
Side and front views of a modern double bass with a French bow. ...
Direction of transmission Unlike ordinary gear trains, the direction of transmission (input shaft vs output shaft) is not reversible, due to the greater friction involved between the worm and worm-wheel, when a single start (one spiral) worm is used. This can be an advantage when it is desired to eliminate any possibility of the output driving the input. If a multistart worm (multiple spirals) then the ratio reduces accordingly and the braking effect of a worm and worm-gear may need to be discounted as the gear may be able to drive the worm.
Applications Worm gears are a compact, efficient means of substantially decreasing speed and increasing torque. Small electric motors are generally high speed and low torque, the addition of a worm and worm-wheel increases the range of applications that it may be suitable for, especially when the worm gears compactness is considered. Rotating magnetic field as a sum of magnetic vectors from 3 phase coils. ...
Worm-drives have also been used in a few automotive differentials. The worm-wheel carries the differential gearing. This protects the vehicle against rollback. This has largely fallen from favour due to the higher than necessary reduction ratios.
Torsen differentials use worm-gears and planetry worm-wheels in place of the bevel gearing in conventional open differentials. The Torsen limited slip differential was invented by American Vernon Gleasman and manufactured by the Gleason Corporation. ...
Input torque is applied to the ring gear, which turns the entire carrier (all blue), providing torque to both side gears (red and yellow), which in turn may drive the left and right wheels. ...
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