Ball bearings

NAME: Ball bearings

ALTERNATIVE NAME/S:

DETAILS/DESCRIPTION: Ball bearings are machine parts that roll over each other in order to prevent friction and make easier forward motion. The concept behind the ball bearing comes from the fact that things move and roll better when they slide, yet sliding also causes friction. Friction slows down motion and does not allow an object to move easily.

In the very early 1900s, Richard Stribeck*, a German professor, pioneered a way for bearings to produce less friction but hold heavier loads. He developed a system to distribute the load between balls so that the friction was minimal.

This is made possible by keeping the moving and stationary parts of a device separated by a track containing freely revolving hard balls. The friction is reduced when the outer piece distributes its load to the ball and then the ball distributes the force to the inner piece. Since the ball is sphere-shaped, it only comes into contact with the inner and outer parts at a very small point. This is what helps to make it move smoothly. But it also means that there is not very much contact area holding the load, so if the bearing is overloaded it is possible for the revolving balls to become damaged.

Stribeck’s ball bearings are one of the most common types of bearing used today. They are found in everyday life in cars, computers, skateboard wheels, and more.

ONELINER: Ball bearings

OTHER CONNECTIONS: None

BIBLIOGRAPHY: Encyclopedia Britannica.; http://science.howstuffworks.com/bearing.htm.; http://history.acusd.edu/gen/recording/berliner.html.

Ball Bearings are thought to have been first conceived by Leonardo DaVinci,but the first patent for a ball bearing system was by Philip Vaughnin 1791. The goal of ball bearings is to reduce friction between moving parts, designed to let two things spin either in opposing directions or at different speeds Another similar method is the use of roller bearings, which are a more general group of friction reducers. The two different types of bearings can be used to hold two basictypes of loads; one in a perpendicular to the axis of rotation which is a thrust bearing, and the other parallel to the axis which is a radial bearing. They can also be arranged in conical formations as well that allow objects to be situated in directions other than parallel or perpendicular. A conical type bearing can be a stronger mount for loads that are attached at an angle that is different than 90 degrees or 180 degrees. This would cause less stress on the bearing itself, helping to reduce friction.

In it’s simplest form,a ball bearing has a few small round metal balls arranged in a circle,but separated by what is called a "cage,"which keeps the balls from binding against each other. The balls and cage are located between two races, which are two circles with groovesfor the balls to run in. One of the races fits on the inside of the balls and cage with a groove on the outer edge for the balls to run on, and the other race fits over the outer edge of the balls and cage and has a groove on the inner edge in which the balls run. This assembly can then be left open to the air or be sealed with a bearing shield to prevent particles from causing extra friction. The whole assembly is typically lubricated, with grease or oil, to help further reduce friction as well as capture any particles that do manage to enter the assembly.

Bearings can be found in all sorts of mechanical constructions: bicycles, automobiles, space shuttles, car wheels, factory machines, earthquake stabilizers, and model cars. (student content)

http://en.wikipedia.org/wiki/Ball_bearing

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For individual balls that are sometimes incorrectly called "ball bearings", see Ball (bearing).