critical speed-bearings

[ccsekaran]

How to calculate critical speed of bearings and gears?

 

[JvdWal]

critical speed [~/min] depends on outside diameter (D) of bearing

D<30: n = {(3 * A) / (D + 30)}* k or,
D_>30: n = {A / (D-10)} * k

A (grease lubrication)
A = 500000; in case of radial ball bearing
A = 360000; in case of double row angular ball bearing
A = 320000; in case of double row ball bearing
A = 250000; in case of double row spherical roller
A = 220000; in case of spherical roller bearing
A = 140000; in case of axial groove bearing

Oil lubrication = A * 1.25

k = 1 if F radial or F axial is smaller than 0.1*C and 0.5<k<1 if 0.4< (Fa/Fr) <100

 

[JvdWal]

I forgot,

Using ceramic balls (Si3N4) makes the critical speed of an deep groove ball bearing 30% higher

 

[AHRBearing]

Bearing cage construction and material will have an effect here, along with the bearings precision grade, ie ABEC 5, 7, 9 HG etc... You would have to consult the appropriate manufactures catalogue in order to gain the correct multipliers. GMN used to do an excellent example in their catalogues.

AHR International Ltd

http://www.ahrinternational.com