Power to overcome bearings resistance

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SUMMARY

The discussion centers on estimating the power required to overcome the resistance of NSK Super Precision Angular Contact Ball Bearings at various RPMs. The dynamic torque formula provided is M_v = f_0 (v_0 n)^{2/3} d_m^3, where M_v represents dynamic torque, f_0 is a dimensionless factor, v_0 is kinematic viscosity, n is speed, and d_m is the pitch circle diameter. Concerns were raised regarding the dimensional analysis of the formula, specifically the absence of a mass unit in the right-hand side of the equation, indicating a potential error in the expression.

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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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