RE: [CAD_CAM_EDM_DRO] Frozen stepper motor shaft

Jarrett!

You've got it! You just don't know it. I am not saying that you multiply
oz-in by anything. I am saying that you GET oz-in by multiplying. That's
what makes it oz-in or "ounces times inches".

Once you know oz-in, you DIVID by the distance in inches to get the
force in ounces.

You can only do that BECAUSE oz-in is gotten by multiplying distance in
inches by force in ounces to get oz-in.

oz-in
-------- = oz
in

Or in english, "ounce inches, divided by inches, give you ounces".

You don't multiply ONCE YOU HAVE ounce inches. You multiply to GET ounce
inches.

Hope this helps.

Andy Wander

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jarrett & Heidi
Johnson
Sent: Sunday, January 22, 2006 1:55 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Frozen stepper motor shaft

I don't intend to dispute, just to clarify in my own mind.

When I use oz-in to calculate my torque from my stepper I multiply?
This seems in reverse to me.
I'm planning on using a 640 oz-in stepper. Now my gearing from this
stepper is a via timing belt.
So.. the pulley attached to my stepper is 1.910 Pitch Dia. so the ARM
of this pully would be the radius at which the belt is located or:
1.910/2 =0.955" So if I have a 640 oz-in stepper this would equate to
640*0.955"=611.2 oz force at that arm distance? So if instead I was to
put my larger pulley on the stepper [ this wouldn't work because I'm
trying to gear down but for sake of discussion]it's a 3.820 Pitch Dia.
so...
3.820/2=1.91" arm then we put this into this same formulat 640 oz-in *
1.91"=1222.4 oz force. It would seem that this is exactly backwards to
how it works, we all go get a long[er] pipe to put on a wrench to get
more ARM distance and get more torque at the bolt. If this is infact the
correct way to calculate this stuff then I've not been doing my
calulations all wrong and my system isn't going to budge when I go to
run it.

Anyway in my mind this oz-in thing should involve division. 640 oz-in
means there is 640 oz of force located at 1" from the center of the
stepper shaft. I don't think anyone disputes this. If the arm was 1/2"
then 640 oz-in/ 0.50"= 1280 oz force you'd cross off the inch's because
it's inches divided by inches and you'd be left with only 'oz' unit's.
If you multiplied this equation you'd be left with oz-in^2. or at least
this is how I see it.

Help!
Jarrett

> Alan:
>
> Yes, I have brought it up before. Some will say I am too picky(I guess

> you are one of them) but it is NOT a division, it is a multiplication,

> that becomes the "unit". If you look into WHY we use "ounce inches" or

> similar terms for torque, you will quickly understand why(1 oz-in of
> torque equates to a 1 ounce force at an inch from the center of
> rotation, but to only 1/2 ounce of force at 2 inches from the center
> of rotation-do the math-you MULTIPLY the ounce by the inches).
>
> If you ever start trying to use these units in a mathematical
> formula(which is not that far out a proposition, considering we are
> attempting to design and build machines that use
> torque) you will get
> hopelessly confused, as the units won't "cancel"
> properly.
>
> The worst part is, that the folks who KNOW it is "ounce-inches", and
> not "ounces per inch", and can shrug off the improper use, won't get
> caught, because they KNOW how to use the formulas and calculations.
> But those who DON'T know the proper terminology are the ones who most
> likely won't be able to make sense out of it.
>
> That's why I think it is important, and will keep bringing it up, as
> long as I think it is important.
>
> Back to the subject at hand, I think your advice to do an ohmmeter
> check on the windings was good, as was that of the other poster who
> recommended making sure none of the leads were touching when trying to

> turn the motors. Until Mike gets back to us on what else he has tried,

> I don't think we can go much further in solving his problem, unless it

> would be to recommend that he checks the shafts where theey exit the
> bearings and motor case for any evidence of corrosion. If they are
> rusted or pitted to the point where that is what is causing sticking,
> theen a good penetrating oil might do the truick.
>
> Andy Wander
> Verrex Corporation
>
> P.S. By the way, I am sure that you know that just because a Google
> search turns up a bunch of mistakes, that doesn't make them suddenly
> become correct.

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