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Self-Changing Gears was a British company, set up and owned equally by Walter Gordon Wilson and John Davenport Siddeley, to develop and exploit the Wilson or pre-selector gearbox. Self-Changing Gears designed, built and licensed transmissions for various applications including light and heavy road vehicles, military, marine, and rail vehicles as well as motor racing cars.
Following the death of Walter Wilson in 1957, his son A Gordon Wilson took over the running of the company until his retirement in 1965.
The original company Improved Gears Ltd was incorporated on 28 December 1928, and this later became Self-Changing Gears (SCG). The company moved a number of times in the early years, and in 1938 settled in premises at Lythalls Lane, Coventry. During World War II, additional premises were used at Burbage, Leicestershire.
In 1935, Siddeley sold his interests in Armstrong Siddeley (including Self-Changing Gears) to Hawker Aircraft forming Hawker Siddeley. In 1951 Leyland Motors bought into the company, resulting in each party owning one-third of the company, and in 1957 Leyland bought-out Hawker-Siddeley's shares, thereby gaining control. In 1986 the business was sold to Cummins. [1]
Many of British Railways' first generation diesel multiple units and shunting locomotives had gearboxes made by Self-Changing Gears. [2] Examples include British Rail Class 100, 03 and 04; some of these are still in use on heritage railways. In the 1980s, SCG gearboxes were fitted to 141, 142, 143,. 144 and 150 class DMUs. [3] [4]
The name Self-Changing Gears is sometimes confusing: the gearboxes are not fully automatic, selection of gear ratio remains a manual choice, but the gear-changing and any clutch control needed is automated. The gearboxes were used in conjunction with a fluid coupling so no clutch pedal was needed.
Gearboxes installed in locomotives built by the Vulcan Foundry for the Drewry Car Company were designated "Wilson-Drewry". [5]
The bus manufacturing industry was a major customer of the company. Buses on city work need to start and stop every minute or less, and the effort required with a manual gearbox was substantial. In addition, for most of the period when these transmissions were dominant buses still had unassisted steering, and the overall effort needed without assistance was fatiguing.
From about 1935 to 1960, buses by AEC, Daimler, and sometimes Bristol, Guy and Leyland offered Preselector gearboxes, either as an option or as standard. London buses invariably used this transmission, along with other cities. Country area buses still commonly retained manual transmissions as they did not have the requirement of constant stopping and starting at bus stops. The London specification included compressed air operation of the change-gear pedal, where others used unassisted operation.
Around 1960, the bus industry was changing from traditional vehicles with engine at the front and driver in a small separate cabin alongside, to entrance at the front alongside the driver, and the engine and gearbox remotely mounted under the floor or at the rear. SCG devised the semi-automatic gearbox, under their brand name "Pneumocyclic" as an advance. It had the same gearbox principle, but instead of pre-selecting a gear and then separately operating a change-gear pedal, both functions were combined and operated from a small lever alongside the steering wheel, the driver merely moving this to the next gear and the transmission responding accordingly. The mechanism was operated either by air pressure or low-voltage electrics and the physical gear-shifting in the gearbox was nearly always by air pressure, though some vehicles used high pressure hydraulics, notably BMMO vehicles. This style of transmission was also widespread in UK buses, from a range of manufacturers, until different types came onto the market in the 1980s. A further advance was the fully automatic gearbox, which still used the same principles but shifted gears automatically. This was pioneered on the AEC Routemaster, and later spread, although not widely, to other vehicle types.
A railcar is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach, with a driver's cab at one or both ends. Some railway companies, such as the Great Western, termed such vehicles "railmotors".
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.
Overdrive is the operation of an automobile cruising at sustained speed with reduced engine speed (rpm), leading to better fuel consumption, lower noise, and lower wear. The term is ambiguous. The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is over-geared, and cannot reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning at higher RPM.
A transmission is a mechanical device which uses a gear set—two or more gears working together—to change the speed, direction of rotation, or torque multiplication/reduction in a machine.
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.
Armstrong Siddeley was a British engineering group that operated during the first half of the 20th century. It was formed in 1919 and is best known for the production of luxury vehicles and aircraft engines.
A semi-automatic transmission is a multiple-speed transmission where part of its operation is automated, but the driver's input is still required to launch the vehicle from a standstill and to manually change gears. Semi-automatic transmissions were almost exclusively used in motorcycles and are based on conventional manual transmissions or sequential manual transmissions, but use an automatic clutch system. But some semi-automatic transmissions have also been based on standard hydraulic automatic transmissions with torque converters and planetary gearsets.
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.
Seddon Atkinson Vehicles Limited, was a manufacturer of large goods vehicles based in Oldham, Lancashire, England, was formed after the acquisition in 1970 of Atkinson Vehicles Limited of Preston by Seddon Diesel Vehicles Limited of Oldham. In 1974, the firm was acquired by International Harvester, which sold it in March 1984 to the Spanish group Enasa which made it a subsidiary of Pegaso. In 1990, it became part of Iveco which used the brand for various types of specialised vehicles in the United Kingdom. The range of models produced included EuroMover, Pacer and Strato, which are aimed at refuse collection, recycling and construction operators.
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.
The Leyland Titan was a forward-control chassis with a front-mounted engine designed to carry double-decker bus bodywork. It was built mainly for the United Kingdom market between 1927 and 1942, and between 1945 and 1969.
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.
A gear stick, gear lever, gearshift or shifter, more formally known as a transmission lever, is a metal lever attached to the transmission of an automobile. The term gear stick mostly refers to the shift lever of a manual transmission, while in an automatic transmission, a similar lever is known as a gear selector. A gear stick will normally be used to change gear whilst depressing the clutch pedal with the left foot to disengage the engine from the drivetrain and wheels. Automatic transmission vehicles, including hydraulic automatic transmissions, automated manual and older semi-automatic transmissions, like VW Autostick, and those with continuously variable transmissions, do not require a physical clutch pedal.
The New Zealand TR class locomotive is a type of diesel shunting locomotives built by many different manufacturers. Defined as "shunting tractors" or "rail tractors" by KiwiRail and its predecessors, they are classified "TR" for tractor as a result. Many of these locomotives have been withdrawn, but some are still in service. The first locomotive of this class was built by NZR in 1924. The most powerful were Japanese-built Hitachi TRs, with 138 kW Cummins engines.
The Leyland Tiger Cub was a lightweight underfloor-engined chassis manufactured by Leyland between 1952 and 1970.
The Daimler Roadliner was a single-decker bus and coach chassis built by Daimler between 1962 and 1972. Notoriously unreliable, it topped the 1993 poll by readers of Classic Bus as the worst bus type ever, beating the Guy Wulfrunian into second place. It was very technologically advanced, offering step-free access some 20 years before other buses; as a coach, it was felt by industry commentators to be in advance of contemporary UK designs.
The Seddon Pennine 7 was a mid-underfloor-engined single-deck bus or coach chassis built by Seddon Atkinson between 1974 and 1982.
The Bristol LH was a single-decker bus chassis built by Bristol Commercial Vehicles (BCV) in Bristol, England. Nearly 2,000 were built between 1967 and 1982 in a variety of sizes and body types, including some as goods vehicles.
A drivetrain or transmission system, is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drivetrain is the components of a motor vehicle that deliver power to the drive wheels. This excludes the engine or motor that generates the power. In marine applications, the drive shaft will drive a propeller, thruster, or waterjet rather than a drive axle, while the actual engine might be similar to an automotive engine. Other machinery, equipment and vehicles may also use a drivetrain to deliver power from the engine(s) to the driven components.
Car controls are the components in automobiles and other powered road vehicles, such as trucks and buses, used for driving and parking.
