Power to overcome bearings resistance

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    Power Resistance
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Discussion Overview

The discussion revolves around estimating the power required to overcome the resistance of NSK Super Precision Angular Contact Ball Bearings when a shaft spins at a given RPM. Participants explore the technical data and formulas related to dynamic torque in this context.

Discussion Character

  • Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant inquires about the possibility of estimating the power needed to overcome bearing resistance at specific RPMs.
  • Another participant suggests downloading the product catalog from NSK, indicating it contains the necessary technical data.
  • Further contributions provide catalog information and reference a formula for dynamic torque that includes a load term and a speed term.
  • A participant expresses confusion regarding the dimensional analysis of the formula for dynamic torque, questioning the absence of a mass dimension in the expression and its implications for the speed term.

Areas of Agreement / Disagreement

The discussion does not reach a consensus, as participants have differing views on the clarity and correctness of the formula provided for dynamic torque.

Contextual Notes

Participants note potential issues with dimensional analysis in the formula, indicating that the relationship between the variables may not be fully resolved.

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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