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Motor Toque caclulation using standard formula

A.DelNegro
4-Participant

Motor Toque caclulation using standard formula

I'm trying to calculate motor torque using a standard equation that includes a constant that obviously has units associated with it, but are not named.

I've pasted an image of the M' sheet as well as attaching the sheet in XPS format.

The basic motor torque formula uses the constant 33000. Does anyone know off hand what units I would need to give this to make the formula come out corredtly? The output is lbf-ft. I did the unit-less calculation underneath the formula so show what the answer should be.

screen_capture-20120913-092510.jpg

1 ACCEPTED SOLUTION

Accepted Solutions

Stuart,

I guess I have to start thinking more out of the box... Your reply gave me an idea...

if M' knows how to convert hp to lbf-ft/min then maybe I dont need the formula anyway. If just let M' do the converting...hmmm

screen_capture-20120913-102131.jpg

So simply deviding the hp but the speed yields the correct answer...!

View solution in original post

5 REPLIES 5

It is an interesting observation that I hp = 33,0000 lbf-ft per minute.

Stuart

Message was edited by: Stuart Bruff ... err, I meant lbf not lb. 😞

Stuart,

I do believe that this is where the number comes from, but if I simply add lbf-ft/min to the equation, I still do not get the correct answer. I now get an answer with Watts in it...

screen_capture-20120913-100949.jpg

Because you are using units the conversion factors are no longer required & do cause the calculation to go significantly wrong.

Regards

Andy

Thanx Andy. One of the reasons I love MathCAD is the units handling. Being a new user, I just have to start thinking differently about how I approach these sorts of problems. Reminds me of when I first started using Pro/E and had to reset my design paradigm.

Stuart,

I guess I have to start thinking more out of the box... Your reply gave me an idea...

if M' knows how to convert hp to lbf-ft/min then maybe I dont need the formula anyway. If just let M' do the converting...hmmm

screen_capture-20120913-102131.jpg

So simply deviding the hp but the speed yields the correct answer...!

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