Holding torque?

[Marc]

A stepper motor with a holding torque of 200(mNm)is aquivalent of how many oz-in

Thanks, Marc..

[BigDaddyG]

Marc,
200 newtons is equal to 719 oz. The mNm is throwing me a little. 200 Millinewtons = .719 oz. Hope this helps.

[BigDaddyG]

Opps I found it - 200 mNm = 28.3 oz/in! And that is my final answer!
Regards,
Glen

[BigDaddyG]

mNm = Milli Newton Meter ( should read mN/m or mN-m).
Regards,
Glen

[Marc]

Thanks a million man

Marc..

[arvidb]

Originally Posted by BigDaddyG mNm = Milli Newton Meter ( should read mN/m or mN-m). Regards, Glen

Ok, you guys can tell me to shut up if you're tired of hearing this...

Torque is the product of force and distance, so writing oz/in or N/m is wrong. (It would imply you could open a door *infinitely* fast by touching it's hinges... and I guess we all know that's not the case).

Also, products in the metric (SI) system is not expressly written, neither with a '-' nor a '*' nor anything else. So 'mNm' is actually the correct way of writing millinewtonmeter. (Although IMO perhaps Nmm [newtonmillimeter] would be nicer...)

Arvid

[miljnor]

Originally Posted by arvidb Ok, you guys can tell me to shut up if you're tired of hearing this... Torque is the product of force and distance, so writing oz/in or N/m is wrong. (It would imply you could open a door *infinitely* fast by touching it's hinges... and I guess we all know that's not the case). Also, products in the metric (SI) system is not expressly written, neither with a '-' nor a '*' nor anything else. So 'mNm' is actually the correct way of writing millinewtonmeter. (Although IMO perhaps Nmm [newtonmillimeter] would be nicer...) Arvid

I don't remember my math from that far back but isn't the designation Oz/In refering to weight over distance moved? I know it is a torque rating but the leverage would change the end result (ie distance from the fulcrum). the closer to the fulcrum the higher the oz. to move. and the less distance. so the formula would self correct? ie the oz. would go up and the distance down? or am i missing something.

[arvidb]

I'm not very comfortable working with pounds and ounces, but think about it this way:
You get more torque by either increasing the force or increasing the distance from the fulcrum. If you divide by the distance, the torque figure will instead *decrease* with longer distances, and reach infinity at zero distance (since you would divide by zero). In the real world, of course, you get zero torque if you apply the force directly on the fulcrum (i.e. at zero distance), and the torque increases linearly with increased distance; thus torque is proportional to both the force and the distance - or, to force and distance multiplied. (Or if you use SI units, torque equals force times distance.)

I'm not sure what you mean by weight over distance moved... torque is force times distance. And oh, ok, weight of course refers to force of gravity of one pound - i.e. the force 1 lbf? But it's not really distance *moved*, it's simply distance from the fulcrum, and it's not "over" but "times". Hmm, maybe I'm being too picky here, english is not my native language

Don't you americans get to learn things like this at school? The dash '-' in your units stands for product, not division.

Arvid

[arvidb]

"ie the oz. would go up and the distance down"

Yes, correct, for equal torque you would need to increase the force if the distance is reduced. But try it:

2 "force" * 5 "distance" = 10 "torque". Increase the force and decrease the distance:
5 "force" * 2 "distance" = 10 "torque". Torque stays the same, as you predicted.

And with the division:

100 "force" / 10 "distance" = 10 "torque". Again increase the force and decrease the distance:
10 "force" / 100 "distance" = 0.1 "torque"! This is clearly not right...

Or taken to its extremes:
1 "force" / 0 "distance" = infinite torque.

Arvid

[miljnor]

Don't you americans get to learn things like this at school? The dash '-' in your units stands for product, not division.

I don't beleive i made any comments on the - verses slash. but yes we do learned stuffs like dat in da schools out her.

I believe that division by 0 is a no-no in math is it not? (damn ders dat "-" again). thus no devision by zero is possible .Butt I aint no enginerrer.

[arvidb]

Yeah, division by zero is a no-no. The result of dividing zero by zero is quite interesting:

x/x = 1
x^2/x = x
x/x^2 = 1/x

and

lim x->0 k/x -> infinity (k > 0)

Set x = 0 in the first three equations and you get 0/0 = 1, 0/0 = 0 and 0/0 = 1/0. The last equation instead hints that the result should reach infinity when the divisor is 0 and the dividend is not zero. So three different results depending on which "proof" you use!

So ok, to be mathematically correct, I should have said this:

'Or taken to its extremes:
lim d->0 1 "force" / d "distance" -> infinite "torque".'

Not as clear, is it?

Arvid

[Marc]

Wow, you guys are really into numbers Just reading all those post gives me a headake

Marc..