Strange (to me) balance spec

[Ralph2]

Can someone decipher what this balance spec is.. or was likely intended to be. From a drawing of the part.. "Dynamic balance @ 190 RPM to maximum 4 oz force"

Do they mean.. a final correction of less than 4 ounces? 4 ounce inches of unbalance?.. Dynamic implies two plane.. this definitely is a static balance job. I have come across a lot of varieties when it comes to balance specifications but this one has me scratching my head.

The part... an agitator (cast), 36 inches in diameter and weighs 2000 pound that spins at 145 RPM.

 

[GregLocock]

I'd read it as that is the maximum acceptable force in the bearings after balancing, at 190 rpm.

4 oz=1N, so the maximum residual imbalance is 2.5 kg mm


Does that make any sense?


Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Ralph2]

Thanks Greg... and no (sorry) how did you arrive at 2.5kg mm?
Metric tolerances confuse me, is that translatable to an ISO 1940 spec? or something in gram inches.
Then I don't know how one would measure that force at the bearings... the bearings are 48 inches apart.. the shaft (solid coupling) is 16 feet 3inches long and the thing spins vertically.
I am currently balancing them (5) overhung and mounted on the shaft.. to an ISO G16 spec (38 kgin)

 

[GregLocock]

F=m*r*w^2

Although thinking about it that's the imbalance force applied to the rotor, it only gets through to the bearings if you assume everything is infinitely stiff.

2.5 kg mm=2500 g mm=100 g in=3 oz in

sorry I don't know about your specs.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.