Bearing Loss Calculation 1

[lengould]

Hi. I need help /confirmation converting bearing loss nmm into watts losses for a small generator. I must have an error somewhere in here, the losses are so large. Problem data: 2 bearings 24.6 cm dia. carrying 747 kg load at 2880 rpm, coeff. fr. .00150 give a frictional moment of 1351 n mm. That much I'm fairly sure of.

Now how many watts will be lost in overcoming 1351 n mm?

My calculation comes to 4.8647 kw, which I think is way too large. What should it be? What steps? Thanks

 

[Skogsgurra]

Hi lengould,

Your 1351 n mm should be written 1.351 Nm (SI doesn't know mm, really)

Your 2880 RPM corresponds to 2880/60 RPS (revolutions per second). But SI does not know RPM or RPS - only radians/second.

To get radians/second, just multiply by 2*PI or 6.28. You will get 301.44 rad/s. Now, multiply torque and rad/s and you will get 301.44*1.352 = 407.24544 or 407 Nm/s (another word for Nm/s is Watt). Your feeling was right. You had way too many watts in your first result.