Total-loss oiling system
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A total-loss oiling system is an engine lubrication system whereby oil is introduced into the engine, and then either burned or ejected overboard. Now rare in four-stroke engines, total loss oiling is still used in many two-stroke engines.
Steam engines
Steam engines used many separate oil boxes, dotted around the engine. Each one was filled before starting and often refilled during running. Where access was difficult, usually because the oil box was on a moving component, the oil box had to be large enough to contain enough oil for a long working shift. To control the flow rate of oil from the reservoir to the bearing, the oil would flow through an oil wick by capillary action rather than downwards under gravity.
On steamships that ran their engines for days at a time, some crew members would be "oilers", whose primary duty was to continuously monitor and maintain oil boxes.
On
Oil recirculation
The first recirculating systems used a collection sump, but no pumped circulation, merely 'splash' lubrication, where the connecting rod dipped into the oil surface and splashed it around. These first appeared on high-speed steam engines. Later, splash lubrication engines added a 'dipper', a metal rod whose only function was to dip into the oil and spread it around.
As engines became faster and more powerful, the amount of oil required became so great that a total loss system would have been impractical, both technically and for cost.
Splash lubrication was also used on the first internal combustion engines. It persisted for some time, even in the first high-performance cars. One of Ettore Bugatti's first technical innovations was a minor improvement to the splash lubrication of crankshafts, helping to establish his reputation as an innovative engineer.
A more sophisticated form of splash lubrication, long used for rotating motor shafts rather than reciprocating engines, was the ring oiler.
Pumped oil
Later systems collect oil in a sump, from where it can be collected and pumped around the engine again, usually after rudimentary filtering. This system has long been the norm for larger internal combustion engines.
A pumped oil system can use higher oil pressures and so makes the use of
Two stroke engines and petroil mixtures
Rotating-crankcase radial engines
Normally known by the term "rotary engine", the usually air-cooled radial configuration, rotating-crankcase Otto cycle engines were used by many "pioneer era" (1903–1914) aircraft and World War I combat aircraft. These engines were designed to have a total-loss lubrication system, with the motor oil held in a separate tank from the fuel in the vehicle, and not pre-mixed with it as with two-cycle engines, but mixed within the engine instead while running. Castor oil was often used because it lubricates well at the high temperatures found in air-cooled engines, and its tendency to gum is of little consequence in a total loss system, since it is constantly being replenished. Unburned castor oil in the exhaust was a cause of digestive complaints in many WWI airmen.[citation needed]