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.
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. [1]
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. [2]
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 of which Professor Hele-Shaw had made an in-depth study. 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 clutches, 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, [3] 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. [4]
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.
The best oil for the Hele-Shaw clutch is Citroen LHS oil. [ citation needed ]
The clutch was introduced for cars and patented in 1905. Clutches were manufactured by the British Hele-Shaw Patent Clutch Co. Ltd. of Oldham. [4] 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. [5] At one time they were universally used on Parisian buses. [3]
The multi-plate Hele-Shaw clutch with six alternating steel and phosphor bronze plates running in graphite powder was used in racecars such as the 1921 Grand Prix Sunbeams. [6] [ clarification needed ]
The Hele-Shaw clutch was also used for extremely high powers in both industry and for marine propulsion, of 1,000 hp and more. [1]
When combined with an epicyclic gearbox, a pair of clutches could form a reversing gearbox. [7] 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.
A clutch is a mechanical device that allows the output shaft to be disconnected from the rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does the work.
An automatic transmission is a multi-speed transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. Vehicles with internal combustion engines, unlike electric vehicles, require the engine to operate in a narrow range of rates of rotation, requiring a gearbox, operated manually or automatically, to drive the wheels over a wide range of speeds.
A torque converter is a device, usually implemented as a type of fluid coupling, that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the prime mover to the automatic gear train, which then drives the load. It is thus usually located between the engine's flexplate and the transmission. The equivalent device in a manual transmission is the mechanical clutch.
A continuously variable transmission (CVT) is an automated transmission that can change through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant angular velocity while the vehicle moves at varying speeds.
A manual transmission (MT), also known as manual gearbox, standard transmission, or stick shift, is a multi-speed motor vehicle transmission system, where gear changes require the driver to manually select the gears by operating a gear stick and clutch.
A limited-slip differential (LSD) is a type of differential gear train that allows its two output shafts to rotate at different speeds but limits the maximum difference between the two shafts. Limited-slip differentials are often known by the generic trademark Positraction, a brand name owned by General Motors and originally used for its Chevrolet branded vehicles.
Engine braking occurs when the retarding forces within an internal combustion engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes.
Hydramatic is an automatic transmission developed by both General Motors' Cadillac and Oldsmobile divisions. Introduced in 1939 for the 1940 model year vehicles, the Hydramatic was the first mass-produced fully-automatic transmission developed for passenger automobile use.
A direct-shift gearbox is an electronically controlled, dual-clutch, multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout, with automated clutch operation, and with fully-automatic or semi-manual gear selection. The first dual-clutch transmissions were derived from Porsche in-house development for the Porsche 962 in the 1980s.
A preselector gearbox is a type of manual transmission mostly used on passenger cars and racing cars in the 1930s, in buses from 1940-1960 and in armoured vehicles from the 1930s to the 1970s. The defining characteristic of a preselector gearbox is that the gear shift lever allowed the driver to "pre-select" the next gear, usually with the transmission remaining in the current gear until the driver pressed the "gear change pedal" at the desired time.
A viscous coupling is a mechanical device which transfers torque and rotation by the medium of a viscous fluid.
A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. 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.
Electromagnetic clutches operate electrically but transmit torque mechanically. This is why they used to be referred to as electro-mechanical clutches. Over the years, EM became known as electromagnetic versus electro-mechanical, referring more about their actuation method versus physical operation. Since the clutches started becoming popular over 60 years ago, the variety of applications and clutch designs has increased dramatically, but the basic operation remains the same today.
A power shuttle is an additional unit used in transmissions and is generally used in agricultural tractors. While the vehicle is moving forwards, the driver can pull a lever that makes it stop and go backwards at the same speed. Power Shuttles are also known under various trade names including Power Reverser
A magnetic particle clutch is a special type of electromagnetic clutch which does not use friction plates. Instead, it uses a fine powder of magnetically susceptible material to mechanically link an otherwise free-wheeling disc attached to one shaft, to a rotor attached to the other shaft.
The Ford PowerShift is a six- or seven-speed dual-clutch automatic transmission, produced by the Ford Motor Company. The older Ford PowerShift gearboxes were built by Getrag Ford Transmissions, a joint-venture with Getrag, however it is unknown who exactly makes the newer 7-speed models. PowerShift improves fuel efficiency by as much as 10 percent when compared to a conventional automatic transmission.
The Beier variable-ratio gear or Beier variator is a mechanical drive offering a continuously variable gear ratio between input and output.
A motorcycle transmission is a transmission created specifically for motorcycle applications. They may also be found in use on other light vehicles such as motor tricycles and quadbikes, go-karts, offroad buggies, auto rickshaws, mowers, and other utility vehicles, microcars, and even some superlight racing cars.
Electromagnetic clutches and brakes operate electrically, but transmit torque mechanically. This is why they used to be referred to as electro-mechanical clutches or brakes. Over the years, EM became known as electromagnetic versus electro mechanical, referring more about their actuation method versus physical operation. Since the clutches started becoming popular over 60 years ago, the variety of applications and brake and clutch designs has increased dramatically, but the basic operation remains the same.
A layshaft is an intermediate shaft within a gearbox that carries gears, but does not transfer the primary drive of the gearbox either in or out of the gearbox. Layshafts are best known through their use in car gearboxes, where they were a ubiquitous part of the rear-wheel drive layout. With the shift to front-wheel drive, the use of layshafts is now rarer.
{{cite journal}}: Missing or empty |title= (help), cited in Kennedy, Modern Engines, Vol. II