Thrust bearing

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A thrust ball bearing

A thrust bearing is a particular type of rotary rolling-element bearing. Like other bearings they permit rotation between parts, but they are designed to support a predominately axial load.

Thrust bearings come in several varieties.

A spherical roller thrust bearing

Thrust bearings are commonly used in automotive, marine, and aerospace applications. They are also used in the main and tail rotor blade grips of RC (radio controlled) helicopters.

Thrust bearings are used in cars because the forward gears in modern car gearboxes use helical gears which, while aiding in smoothness and noise reduction, cause axial forces that need to be dealt with. The double helical or herringbone gear balances the thrust caused by normal helical gears.

One specific thrust bearing in an automobile is the clutch "throw out" bearing, sometimes called the clutch release bearing.

Fluid film thrust bearings[edit]

Exploded view of a Michell type thrust bearing. Note, each sector shaped pad can pivot on the ridges on the lower plate

Fluid-film thrust bearings were invented by Australian engineer George Michell (pronounced Mitchell) who patented his invention in 1905. Michell bearings contain a number of sector-shaped pads, arranged in a circle around the shaft, and which are free to pivot. These create wedge-shaped regions of oil inside the bearing between the pads and a rotating disk, which support the applied thrust and eliminate metal-on-metal contact.

Michell's invention was notably applied to the thrust block in ships. The small size (one-tenth the size of old bearing designs), low friction and long life of Michell's invention made possible the development of more powerful engines and propellers. They were used extensively in ships built during World War I, and have become the standard bearing used on turbine shafts in ships and power plants worldwide. (See also Michell/Kingsbury tilting-pad fluid bearings)

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References[edit]

  1. ^ "Why SKF Spherical roller thrust bearings". SKF. Retrieved 17 December 2013.