Curious..........Is there a comparison or conversion for oz-in/lb into Mils for balancing purposes, or is this not possible?

This message has been edited. Last edited by: DGronski,

Maybe you have more luck than me, checkout:
* http://www.onlineconversion.com/torque.htm
* http://www.processassociates.com/process/convert/cf_all.htm

Grono,

To keep you units consistent, you want Mils/lb. From ISO 1940 Balance Tolerance chart: 1-Mil/lb = .454 g-in/lb where Mil is ).001 inches of rotor eccentricity, lb is rotor weight in lbs, g is grams mass. Yo can do the conversion between grams and oz.

Walt

Walt is probably correct as always but I didnt exactly understand it. Let me try it my way and someone please tell me if I'm right or wrong.

m*r = M*e

m*r/M =e


If you had m*r in pound-inch, M in pounds, and e in inches, you wouldn't have to worry about units... units would cancel without any conversions.

If you want m*r in ounce inch, M in pounds, e in mils (thousandths of an inch), then you need conversions 16 ounces per pound 1000 mils per inch


(m*r/16) / M = e/1000

m*r/M = e * 16/1000 = 0.016*e
(where m*r in inch-pound, M in pound, e in mils)

one ounce-inch per pound is the same balance spec as 0.016 mils = 0.000016 inch

Is that right?

If you are looking for a conversion from mils measured on the bearing housing after the machine has been rebuilt and oz-ins measured on the balancing machine, then the answer to your question is NO.

Bearing housing stiffness plays a major part in determining how rotor unbalance (in oz-ins)translates into casing vibration (in mils) and this will vary greatly from one design of machine to another.

That's a good clarification - field vibration measurment is a much different thing than balance spec.

However, the question did say "for balancing purposes." Mils can be an unbalance specification given to the balance machine oeprator. In that case the formula is e=m*r/M. m*r/M is specific unbalance (unbalance per pound of rotor weight). Maximum allowable specific unbalance varies with speed for a given balance grade. Unit analysis shows that specific unbalance can be given in units of length.

Pete,

e= (m*r)/M

1000 mils= (16 oz*in)/16 oz

62.5 mils= (1 oz*in)/16 oz

Alec
You are right.

I wrote:
"m*r/M = e * 16/1000 = 0.016*e
(where m*r in inch-pound, M in pound, e in mils)"
That was right.... agrees with what you said.

Then I wrote:
"one ounce-inch per pound is the same balance spec as 0.016 mils = 0.000016 inch"
That was wrong.

I should have said:
one mil in the same balance spec as 0.016 inch-ounce per pound.

or multiply both sides by 1/0.016=62.5 to give equivalent expression:
62.5 mils = 1 inch-ounce per pound.