The Basics of Bearing Loads

Bearings are given their name because the balls inside the bearings have to ‘bear’ the weight of objects and because of the way they are made, bearings offer the perfect solution for bearing the weight of heavy or intricate machinery whilst still being able to rotate. The load that bearings will have to carry greatly influences the choice of bearings as the size of the ball, the amount of balls and the type of bearing all vary depending on the load which needs to be carried and whether the load is a thrust or radial load.

Bearing loads typically fall into two categories, radial and thrust and which bearings are used depends on where the bearing will be and therefore the load it will be subjected to. For example, radial loads are associated with bearings that support pulleys and motor shafts whereas thrust load bearings support weight which is pressed down on them, for example the weight of a person wearing roller skates would create a thrust load on the bearings in the wheels of the skates. In some cases, such as with a vehicle wheel, bearings experience both radial and thrust loads – the thrust load comes from the force associated with taking corners and the radial load comes from the weight of the vehicle. Ball bearings are able to take the load of both thrust and radial pressure; roller bearings are more suited to handle radial loads and tapered roller bearings are usually found in vehicle wheels so are suitable for thrust load.

Another factor which comes into play with bearing loads is bearing lubrication, as oil or grease based lubricants help to prolong the life of bearings, whether they operate a sliding or rolling action, as the lubricant provides a film which keeps the moving parts of the bearings separate from their load. Some bearings such as hydrostatic and hydrodynamic bearings can last indefinitely as they are self lubricating and the film of lubrication builds up as the bearings rotate giving them superb protection.