The Beier variable-ratio gear or Beier variator is a mechanical drive offering a continuously variable

gear ratio A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage. Gear teeth are designed to ensure the Pitch circle diameter (gears), pitch circles of e ...

between input and output. The gear relies on the inter-meshing of a number of thin disks. By varying their separation, the effective radius of one disk varies, thus changing the overall gear ratio. This varying-radius principle is shared by a number of other

variator A variator is a device that can change its parameters, or can change parameters of other devices. Often a variator is a mechanical power transmission device that can change its gear ratio continuously (rather than in steps). Examples * Beier ...

mechanisms. An advantage of the Beier is that a large number of disks may be stacked on a common shaft, thus increasing its

torque In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

capacity for only a small increase in overall length. The mechanism consists of a spring-loaded stack of thin disks on a central shaft. Around this are arranged other stacked disk packs on a number of planetary shafts, usually three. These shafts are mounted on swinging arms, so that they may be moved in and out together. The central disks are thin, with a thickened rim. The planet disks are tapered across their radius, at an included angle of around 3°. When the disks are intermeshed, they thus only contact at the rim of the central pack, no matter what the spacing of the shafts. These planetary disk packs have a gear meshing with a gear on the swing arms' fulcrum shafts, which in turn meshes with a central gear, used for the input drive. The central shaft is the output shaft and the gear is used as a reduction gear. When the disks are moved outwards, the central rim drives on the outside radius of the similar-sized tapered disks and the overall ratio is around 1:1. As the swing arms are moved inwards, the tapered disks are forced between the central rims against their spring-loading. The effective radius of the tapered disks is thus reduced and the gear ratio increases. The gear is made in a variety of ratio ranges, typically from 3:1 to 10:1. Overall efficiency is good, greater than 90%. Unlike most other variators, but in common with the

Hele-Shaw clutch The Hele-Shaw clutch was an early form of multi-plate wet clutch, in use around 1900. It was named after its inventor, Professor Henry Selby Hele-Shaw, who was noted for his work in viscosity and flows through small gaps between parallel plate ...

, the Beier gear does not rely on

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

between the disks, but rather on

viscous Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for example, syrup h ...

drag through a thin oil film between them. This has little slip, less than 1%, and the lack of friction reduces the losses through heat and thus permits a small compact mechanism to still handle a high power. Oil is often pumped through the drive, also having a cooling effect.

Applications

The drive was developed by Dr Beier, an Austrian working in Germany. Some of its first applications were as an

automatic transmission An automatic transmission (AT) or automatic gearbox is a multi-speed transmission (mechanics), transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. The 1904 ...

in buses. In 1951, it was used in the E.145

Napier Nomad The Napier Nomad is a British diesel engine, diesel aircraft engine designed and built by Napier & Son in 1949. They combined a piston engine with a turbine to recover energy from the exhaust and thereby improve fuel efficiency, fuel economy. T ...

aero engine. This was a complex

turbo-compound engine A turbo-compound engine is a reciprocating engine that employs a turbine to recover energy from the exhaust gases. Instead of using that energy to drive a turbocharger as found in many high-power aircraft engines, the energy is instead sent to ...

that coupled a diesel piston engine together with a gas turbine and axial-compressor

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement (engine), displacement. It is a form of forced induction that is mechanically ...

. Supercharging boost control was achieved by varying the ratio of this drive. In contemporary use, the Beier variator is most widely used as part of an industrial motor drive. An electric induction motor is driven at its ideal speed, derived from the electrical line frequency, and the variator drive is used to manually adjust its output speed. These are often coupled with a

cycloidal drive A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the speed of an input shaft by a certain ratio. Cycloidal speed reducers are capable of relatively high ratios in compact sizes with very low backlash. The input shaft dr ...

to provide an extra-low speed output.

References

{{Reflist Variators Mechanical devices using viscosity

Applications

See also

References