Hele-Shaw clutch
Encyclopedia
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 plates
. The clutch was innovative in not relying upon friction
, as other clutches did.
In the Hele-Shaw clutch, the many plates are lightweight pressings from thin sheets of steel. Each plate has a ring pressed into it, V-shaped in section and forming a frustum
of a cone with each side. The clutch is always used wet, so that there is a very thin layer of oil between the plates, even when compressed. For high powers there may be a great many of these plates, necessitated by the driving torque through of the keying teeth. The 1908 Itala Grand Prix car had a clutch with 64 plates.
The innovation of the Hele-Shaw clutch is that it does not operate by friction
, as for most other clutches, but rather by the viscous flow behaviour that Professor Hele-Shaw had made such a study of. When the plates are pressed together closely enough, the film between the plates is thin enough that the drag between them is sufficient to transmit the drive without slipping. Although there may be some slight slip in practice, unlike the fluid coupling
there is no requirement for such slip to generate the flow velocity that the coupling depends upon, and so the Hele-Shaw clutch may approach a theoretical 100% efficiency.
Frictional clutches, usually leather-faced cone clutch
es, were in use before the Hele-Shaw clutch. Their difficulty was one of materials science and the lack of a suitable friction material, before asbestos clutch linings, that could handle the specific power / area at an elevated operating temperature
. As the Hele-Shaw clutch did not rely on friction, it generated only a fraction of the heat of other designs and its construction was easily able to disperse this.
Both the multi-plate and the wet clutch were also in use beforehand. The innovation of the Hele-Shaw clutch is that the multiple plates were an inherent feature of the design, and also simple to manufacture, rather than being a crude duplication of multiple elements that were individually underpowered. The use of oil was also inherent, unlike other clutches that still basically relied on dry friction, with lubrication to avoid overheating when slipping.
. Its advantages were soon recognised, particularly its reliability and resistance to overheating when in heavy use. At a Paris motor show in 1907, around 80% of the cars exhibited used the Hele-Shaw clutch. At one time they were universally used on Parisian buses.
When combined with an epicyclic gearbox, a pair of clutches could form a reversing gearbox., cited in Kennedy, Modern Engines, Vol. II Engaging each clutch in turn provided a forwards and reverse motion, one direction being geared down in speed and increased in torque. As the clutches could be engaged quickly with only a light controlling force, these gearboxes became widely used in heavy steel rolling mills, where the rollers are driven forwards requiring full power, then quickly in reverse.
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
, in use around 1900. It was named after its inventor, Professor Henry Selby Hele-Shaw
Henry Selby Hele-Shaw
Henry Selby Hele-Shaw FRS was an English mechanical and automobile engineer. He was the inventor of the variable-pitch propeller, which contributed to British success in the Battle of Britain in 1940, and he experimented with flows through thin cells. Flows through such configurations are named in...
, who was noted for his work in viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
and flows through small gaps between parallel plates
Hele-Shaw flow
Hele-Shaw flow is defined as Stokes Flow between two parallel flat plates separated by an infinitesimally small gap. Various problems in fluid mechanics can be approximated to Hele-Shaw flows and thus the research of these flows is of importance. Approximation to Hele-Shaw flow is specifically...
. The clutch was innovative in not relying upon friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
, as other clutches did.
Description
The clutch appears outwardly similar to most other multi-plate clutches. A stack of plates is enclosed in a housing with a divided central shaft. Alternate plates are keyed to either the input or output shafts, through either the inner or outer housings. A pressure plate is arranged at one end of the stack so that an axial force may be applied, compressing the stack and causing it to transmit the drive. Releasing the pressure releases the clutch.In the Hele-Shaw clutch, the many plates are lightweight pressings from thin sheets of steel. Each plate has a ring pressed into it, V-shaped in section and forming a frustum
Frustum
In geometry, a frustum is the portion of a solid that lies between two parallel planes cutting it....
of a cone with each side. The clutch is always used wet, so that there is a very thin layer of oil between the plates, even when compressed. For high powers there may be a great many of these plates, necessitated by the driving torque through of the keying teeth. The 1908 Itala Grand Prix car had a clutch with 64 plates.
The innovation of the Hele-Shaw clutch is that it does not operate by friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
, as for most other clutches, but rather by the viscous flow behaviour that Professor Hele-Shaw had made such a study of. When the plates are pressed together closely enough, the film between the plates is thin enough that the drag between them is sufficient to transmit the drive without slipping. Although there may be some slight slip in practice, unlike the fluid coupling
Fluid coupling
A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch...
there is no requirement for such slip to generate the flow velocity that the coupling depends upon, and so the Hele-Shaw clutch may approach a theoretical 100% efficiency.
Frictional clutches, usually leather-faced cone clutch
Cone clutch
A cone clutch serves the same purpose as a disk or plate clutch. However, instead of mating two spinning disks, the cone clutch uses two conical surfaces to transmit torque by friction....
es, were in use before the Hele-Shaw clutch. Their difficulty was one of materials science and the lack of a suitable friction material, before asbestos clutch linings, that could handle the specific power / area at an elevated operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
. As the Hele-Shaw clutch did not rely on friction, it generated only a fraction of the heat of other designs and its construction was easily able to disperse this.
Both the multi-plate and the wet clutch were also in use beforehand. The innovation of the Hele-Shaw clutch is that the multiple plates were an inherent feature of the design, and also simple to manufacture, rather than being a crude duplication of multiple elements that were individually underpowered. The use of oil was also inherent, unlike other clutches that still basically relied on dry friction, with lubrication to avoid overheating when slipping.
Cars
The clutch was introduced for cars and patented in 1905. Clutches were manufactured by the British Hele-Shaw Patent Clutch Co. Ltd. of OldhamOldham
Oldham is a large town in Greater Manchester, England. It lies amid the Pennines on elevated ground between the rivers Irk and Medlock, south-southeast of Rochdale, and northeast of the city of Manchester...
. Its advantages were soon recognised, particularly its reliability and resistance to overheating when in heavy use. At a Paris motor show in 1907, around 80% of the cars exhibited used the Hele-Shaw clutch. At one time they were universally used on Parisian buses.
Reversing clutches
The Hele-Shaw clutch was also used for extremely high powers in both industry and for marine propulsion, of 1,000 hp and more.When combined with an epicyclic gearbox, a pair of clutches could form a reversing gearbox., cited in Kennedy, Modern Engines, Vol. II Engaging each clutch in turn provided a forwards and reverse motion, one direction being geared down in speed and increased in torque. As the clutches could be engaged quickly with only a light controlling force, these gearboxes became widely used in heavy steel rolling mills, where the rollers are driven forwards requiring full power, then quickly in reverse.