Coffman starter
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The Coffman engine starter (also known as a "shotgun starter") was a starting system used on many
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
engines in aircraft and armored vehicles of the 1930s and 1940s. It used a
cordite Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace black powder as a military propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burni ...
cartridge to move a piston, which cranked the engine. The Coffman system was one of the most common brands; another was the Breeze cartridge system, which was produced under Coffman patents. Most American military aircraft and tanks which used radial engines were equipped with this system. Some versions of the
Rolls-Royce Merlin The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litres (1,650  cu in) capacity. Rolls-Royce designed the engine and first ran it in 1933 as a private venture. Initially known as the PV-12, it was later ...
engine used in the
British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and other Allied countries before, during, and after World War II. Many variants of the Spitfire were built, from the Mk 1 to the Rolls-Royce Grif ...
used the Coffman system as a starter. The
Hawker Typhoon The Hawker Typhoon is a British single-seat fighter-bomber, produced by Hawker Aircraft. It was intended to be a medium-high altitude interceptor, as a replacement for the Hawker Hurricane, but several design problems were encountered and i ...
and
Hawker Tempest The Hawker Tempest is a British fighter aircraft that was primarily used by the Royal Air Force (RAF) in the Second World War. The Tempest, originally known as the ''Typhoon II'', was an improved derivative of the Hawker Typhoon, intended to ...
also used the Coffman system to start their
Napier Sabre The Napier Sabre is a British H-24-cylinder, liquid-cooled, sleeve valve, piston aero engine, designed by Major Frank Halford and built by D. Napier & Son during World War II. The engine evolved to become one of the most powerful inline ...
engines. Cartridge starters used on a number of
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s, including such engines as the
Rolls-Royce Avon The Rolls-Royce Avon was the first axial flow jet engine designed and produced by Rolls-Royce. Introduced in 1950, the engine went on to become one of their most successful post-World War II engine designs. It was used in a wide variety of ai ...
, which were used in the
English Electric Canberra The English Electric Canberra is a British first-generation, jet-powered medium bomber. It was developed by English Electric during the mid- to late 1940s in response to a 1944 Air Ministry requirement for a successor to the wartime de Havil ...
and
Hawker Hunter The Hawker Hunter is a transonic British jet-powered fighter aircraft that was developed by Hawker Aircraft for the Royal Air Force (RAF) during the late 1940s and early 1950s. It was designed to take advantage of the newly developed Rolls-R ...
aircraft, used a high gas volume cartridge driving a turbine instead of a piston. Some
Snowcat A snowcat (short for snow and caterpillar) is an enclosed-cab, truck-sized, fully tracked vehicle designed to move on snow. Major manufacturers are Pisten Bully (Germany), Prinoth (Italy) and Tucker (United States). Snow groomers A snow ...
and similar vehicles used in extreme low temperatures were historically equipped with cartridge start.


Design

The Coffman device used a large
blank cartridge A blank is a firearm cartridge that, when fired, does not shoot a projectile like a bullet or pellet, but generates a muzzle flash and an explosive sound ( muzzle report) like a normal gunshot would. Firearms may need to be modified to allow a bl ...
containing Cordite that, when fired, pushed a piston forward. A screw thread driven by the piston engaged with the engine, turning it over. This was in contrast with other type of cartridge starter which acted directly to drive the engine piston down and so turn the rest of the engine over, such as those used on the
Field-Marshall Field-Marshall was a brand of farm tractor which was manufactured by Marshall, Sons & Co. of Gainsborough, Lincolnshire in the United Kingdom. Field-Marshalls were in production from 1945 to 1957. However, the first single-cylinder Marshall ca ...
agricultural diesel tractor. The other systems used during the period were electric motors (such as those used in automobiles today), inertia starter (cranked either by hand or an electric motor) and compressed-air starters, which operated much like Coffman starters but were powered by pressurized air tanks. Shotgun starters are composed of a breech, into which the cartridge is inserted, which is connected to the motor by a short
steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
pipe, which acts like a gun barrel. The blank cartridge fits into the breech, and is triggered either electrically or mechanically. When the aircraft's ignition is turned on and the cartridge is fired, high-velocity, high-pressure gas (~ at ~) shoots down the pipe, forcing the motor to spin and engage the starter ring gear on the engine, which is attached to the crankshaft. Shotgun starters had several advantages over other starting systems in use at the time. Electric starters required large, heavy, and often troublesome batteries to be carried on board, or external charging equipment had to be located at every place where the vehicle was anticipated to operate. Inertia starters used a heavy wheel, usually made of brass, which was spun by a hand crank or electric motor, causing the spinning wheel to engage the starter ring gear. The Coffman system was more lightweight and compact than inertial starters or internal batteries, and it did not require any special auxiliary equipment, an important feature when operating in remote areas. The primary disadvantages of the shotgun starter are the need to keep a stock of cartridges, one of which is used for each attempt to start, and the short time that the motor is spun by each cartridge. Compressed-air starters, which use the same type of motor, are usually recharged by an engine-driven compressor, negating the need to carry cartridges, but adding requirements for the compressor and air tank. Hybrid systems can be made simply by adding a cartridge breech or an air tank to an existing system. Air tanks can also be recharged from an external source in an emergency, such as a hand pump or a portable air compressor. The Coffman starter was the most common brand of cartridge starters during the mid-1930s, and the name was used as a generic description. Advances in electrical technology have made shotgun starters obsolete for most uses.


See also

* Air-start system *
Flame holder A flame holder is a component of a jet engine designed to help maintain continual combustion. In a scramjet engine the residence time of the fuel is very low and complete penetration of the fuel into the flow will not occur. To avoid these conditio ...


References


External links

* * {{DEFAULTSORT:Coffman Engine Starter Starting systems de:Anlasser#Coffman-Starter