An engine has two things constantly working against it, Friction and Heat. If either one is allowed to get out of control the engine will be severely damaged.
Friction – Resistance to motion when two surfaces move against each other. The amount of friction is affected by the finish of the surface (smooth or rough) and the amount of force applied. It should be noted that even very fine or smooth surfaces have defects and irregularities at a microscopic level. In an engine, friction reduces the maximum power output and fuel efficiency of an engine and it also creates heat buildup.
An engine can produce over 6000PSI on a wrist pin during operation.
An engine can produce over 6000PSI on a wrist pin during operation.
Sliding Friction – Sliding friction is present in plain bearings and bushings. This type of friction is created when object slide against each other and can be found on cylinder walls when piston & rings move, Cam shafts.
Rolling Friction – Rolling friction is found in bearings such as ball bearings, needle bearings and roller bearings.
All surfaces (even with a smooth finish) have microscopic hills and valleys or bumps. Lubrication fills in these hills and valleys so that they do not interlock during motion. In a ball bearing, it is not uncommon for the race, or the balls to have very small defects. The lubricant allows the ball to float over the tiny defects in the face to reduce friction. Essentially a good lubricant keeps direct contact between surfaces to a minimum. Some components inside the engine move very fast and lubrication is vital. A needle inside a needle bearing may rotate up to 10X faster than the engine speed. If an engine is operating at 3000RPM, a needle may be turning at 30,000RPM.
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