Power to overcome bearings resistance

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Estimating the power required to overcome the resistance of NSK Super Precision Angular Contact Ball Bearings involves understanding dynamic torque, which is influenced by load and speed. The formula provided for dynamic torque includes variables such as a dimensionless factor, kinematic viscosity, speed, and pitch circle diameter. Concerns were raised about the dimensional analysis of the formula, particularly the absence of mass units on the right-hand side, suggesting a potential error. Clarification is needed on how the speed variable relates to mass. Accurate calculations are essential for determining the power needed at specific RPMs.
Sunfire
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Hello,

I have a pair of bearings (NSK Super Precision Angular Contact Ball Bearings) and was wondering whether I would be able to estimate the power it takes to overcome the bearings resistance when the shaft spins with some given rpm.

Are you aware if this is possible to estimate. Thanks!
 
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Download the product catalog from the NSK website. That has the technical data to answer the question.
 
Here is the catalog info...
 

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Sunfire said:
Here is the catalog info...
... and the formula using the factor f_0 is in Part 5 Section 6.
 
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Thank you :smile:

The dynamic torque is given by a load term and a speed term.
The speed term is:
##M_v = f_0 (v_0 n)^{2/3} d_m^3##, but its dimensional analysis has left me wondering.

##M_v## - dynamic torque, dimension [N.m]
##f_0## - some factor, dimensionless
##v_0## - kinematic viscosity, [##m^2##/s]
##n## - speed, [?]
##d_m## - pitch circle diameter of rolling element, [m]

Lhs requires a [kg] to appear somewhere in the Rhs. Probably something is amiss with the above expression. I cannot imagine [kg] has anything to do with the "speed" ##n##?
 
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