Simple coefficient of friction question

AI Thread Summary
The discussion focuses on calculating the coefficient of friction for a motor shaft under specific conditions. The user provides details including no load and loaded torque, surface area, mass, and rotational speed. They derive the resistive force from the difference between loaded and no load rotational forces. The coefficient of friction is calculated as 0.0428, which the user believes is realistic given the materials involved. Confirmation and further insights on the calculation are sought from the forum.
jmart157
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Here's my givens... i need to find the coefficient of friction on the material.

No load torque on motor - 3.19 Nm
Loaded torque on motor - 3.49 Nm
Surface area in contact with motor shaft - .1885"
Mass of loaded material on shaft - 17.16 lbs = 76.33 N
Rads/sec - 31.42Looking to find the coefficient of friction. I need formulas and assistance please, not answers :)

Also, if I need to get/provide more information, I believe I can.

Jon
 
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alright, this came too easy. please confirm...

torque = Radius x force

which means rotational force = torque/radius

loaded rotational force = 41.83/2" = 20.92 lbsf
no load rotational force = 38.25/2" = 19.123 lbsf

resistive force from load = 20.92 lbsf - 19.123 lbs f = 1.7928 lbs

coefficient friction is (resistive force divided by rotational force) divided by 2

CoF = (1.7928/20.92)/2 = 0.0428

This seems realistic as this is plastic wearing against polished steel, in hot water. What do you guys think?
 

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