Today, friction whether static or dynamic, is reliant on bearings to reduce motor or engine load. What is sometimes overlooked is inherent features and design of a bearings to reduce temperature where it is not necessary. The basic requirement is to reduce contacting surface areas. More extreme requirements are to reduce vibration, reduce allotted space required to house such a bearing, and extend their life.

Needle roller bearings are used where load is spread length ways, and a typical or common application would be “big end” bearings of motorcycles. Plain bearings are still used in big ends, of cars and most other crankshaft scenarios. The principle behind a plain bearing is that thinner a material is, harder it is to compress or displace it. Plain bearings, often called bushings, can be “steel backed” with a relatively thin coating of white metal applied to bearing contact surface. This would be common type in automotive big end applications, and should a piece of offensive hard material contaminate oil, it can be safely embedded within white metal. Should it be small enough then it is not an issue.

More plain bearings can be of a bronze base with impurities cast or sintered into them. The purpose is to absorb oil or lubricant before application, and become “self-lubricating, for a limited time anyway.

Many years before industrial revolution, bearings were made from anything available that was considered appropriate. Timber, sometimes from apple trees but not in any way exclusive to them, have been used in windmills and water mills.

Indeed, stone bushings were not unusual. You’ve heard of more expensive watches been said to contain “X number of Jewels”? The purpose of such jewels was to reduce friction and associated loads. This would be a loose example of metal to stone contact.

Thrust bearings are designed to work through a different axis, and may be ball-type, cylindrical roller type or a combination of both. Taper roller bearings are an example.