Components - Bearings

Question	Answer
Plain	In its simplest form, a plain bearing is just a support which holds a rotating shaft. However because of friction, sooner or later the shaft or support would wear down and cause further inefficient spinning or catastrophic failure of the entire system. For this reason, a sleeve of low friction material is put around the shaft to reduce wear. This is called a bush.
Bush	The most common bearing material (see its use in 'Plain' bearings) is bronze - an alloy of 90% copper and 10% tin. However, more modern material are increasingly being used - such as nylon which is 'self lubricating' and some sintered ceramics (see materials revision section). The advantage of sintered ceramics is that if that they will be extremely heat resistant, and if porous, will soak up oil to lubricate the bearing. However all bushes will need replacing after time.
Journal	A journal bearing is similar to a plain bearing. However, rather than a bush insert, there is a layer of grease or oil between the shaft and the support. The grease or oil is very thick and thus the shaft and support never touch. To ensure good working order, regular maintenance must be carried out where oil or grease is fed under pressure into the bearing via a small hole.
Ball Bearing	One of the commonest forms of bearing. Consists of an inner race which grips the shaft (Eunice), surrounded by steel balls in a ball cage, which are able to roll against the outer race (which could be held by the support).

Resource summary

	Created by Alec Stevens over 11 years ago