Fluid coupling
It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.
Dr Gustav Bauer of the Vulcan-Werke collaborated with English engineer Harold Sinclair of Hydraulic Coupling Patents Limited to adapt the Föttinger coupling to vehicle transmission in an attempt to mitigate the lurching Sinclair had experienced while riding on London buses during the 1920s[2] Following Sinclair's discussions with the London General Omnibus Company begun in October 1926, and trials on an Associated Daimler bus chassis, Percy Martin of Daimler decided to apply the principle to the Daimler group's private cars.
[3] During 1930 The Daimler Company of Coventry, England began to introduce a transmission system using a fluid coupling and Wilson self-changing gearbox for buses and their flagship cars.
[3] In 1939 General Motors Corporation introduced Hydramatic drive, the first fully automatic automotive transmission system installed in a mass-produced automobile.
Under stall conditions all of the engine's power at that speed would be dissipated in the fluid coupling as heat, possibly leading to damage.
When the output shaft begins to rotate, the oil is thrown out of the reservoir by centrifugal force, and returns to the main body of the coupling, so that normal power transmission is restored.
Fluid couplings can also act as hydrodynamic brakes, dissipating rotational energy as heat through frictional forces (both viscous and fluid/container).
An under-filled coupling will be unable to transmit the full torque, and the limited fluid volume is also likely to overheat, often with damage to the seals.
[b] Controlling the fill level is done with a 'scoop', a non-rotating pipe which enters the rotating coupling through a central, fixed hub.
Self-Changing Gears made semi-automatic transmissions for British Rail, and Voith manufacture turbo-transmissions for diesel multiple units which contain various combinations of fluid couplings and torque converters.
In this regard, the behaviour of the fluid coupling strongly resembles that of a mechanical clutch driving a manual transmission.
Fluid flywheels, as distinct from torque converters, are best known for their use in Daimler cars in conjunction with a Wilson pre-selector gearbox.
Daimler and Alvis were both also known for their military vehicles and armoured cars, some of which also used the combination of pre-selector gearbox and fluid flywheel.
The most prominent use of fluid couplings in aeronautical applications was in the DB 601, DB 603 and DB 605 engines where it was used as a barometrically controlled hydraulic clutch for the centrifugal compressor and the Wright turbo-compound reciprocating engine, in which three power recovery turbines extracted approximately 20 percent of the energy or about 500 horsepower (370 kW) from the engine's exhaust gases and then, using three fluid couplings and gearing, converted low-torque high-speed turbine rotation to low-speed, high-torque output to drive the propeller.
Stop-and-go driving will tend to operate the coupling in its least efficient range, causing an adverse effect on fuel economy.
Manufacturers of industrial fluid couplings include Voith,[14] Transfluid,[15] TwinDisc,[16] Siemens,[17] Parag,[18] Fluidomat,[19] Reuland Electric[20] and TRI Transmission and Bearing Corp.[21] This is not an exhaustive list but is intended to give an idea of the development of fluid couplings in the 20th century.
