The Lubrication of Combustion Engines
Friday, 03 February 2012 @ 11:39 AM ICT
Contributed by: news

The lubrication of internal combustion engines began with the need to prevent moving parts from damaging each other. As one surface slides or rolls against another, extreme temperatures are generated in the very small regions in which the high points of one surface contact those of the other. Metals melt and fuse, forming micro-welds. These welds are broken by the further motion of the parts, generating surface damage and liberating wear particles.Even a tiny amount of lubricant can prevent most of this by forming a film which separates the parts very slightly. This greatly extends parts life. One example is wheel bearings, which because they turn slowly and generate little heat can be lubricated by grease. Grease is a mixture of a soap, which provides structure, and oil, which is the lubricant. The gearboxes of many motorcycles through about 1935 were likewise lubricated by grease. As friction and parts motion generated heat, oil melted out of the grease to form lubricating films.
As machine parts move faster, the ability of grease to adhere to them disappears and oil must be conveyed to where it is needed in some other way. The earliest engines were lubricated by 'splash' - pouring a liter or less oil into the crankcase and allowing the motion of the rotating crank to throw it everywhere. Small guides were often cast into the inner surfaces of the crankcase to channel oil to holes that led to the main bearings. As oil made its way past piston rings and thence out of the engine, more had to be provided from a small tank by a hand pump. This was operated by a vigilant rider who looked back often. If there were no smoky trail, the engine needed a shot of oil.














