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NSS
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Torque Calculation

03/26/2018 3:13 PM

I am a little scared right now. may go to the doc for a checkup because I have been doing this for all my life. And right now I am not sure I am doing it correctly, The image below is a simple torque calculation.

The red arrow is say the motor shaft. The far right if the weight pushing down on that end of that arm.

the distance is also seen, the weight is in ounces.

Am I calculating this correctly that the in/oz torque for this example is 3.515 in/oz?
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user-deleted-1105
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#1

Re: Torque Calc,

03/26/2018 3:37 PM

Assuming you mean the shaft is coming straight of the screen... (and not running in the direction of the arrow)

Of course you are doing it right!
Del

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#16
In reply to #1

Re: Torque Calc,

03/28/2018 4:53 AM

It doesn't matter, it's the same torque. If the shaft is coming out of the screen it's a twisting or torsional moment, if it's in the plane of the paper it's a bending moment.

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PWSlack
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#2

Re: Torque Calc,

03/26/2018 4:16 PM

"Every couple has its moment" - Anon.

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#11
In reply to #2

Re: Torque Calc,

03/27/2018 10:01 AM

Nice pun!

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#3

Re: Torque Calc,

03/26/2018 4:22 PM

Units of torque are force times distance, so it should be 3.515 oz in, not 3.515 in/oz. Other than that, your OK.

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MR. Guest
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#5
In reply to #3

Re: Torque Calc,

03/26/2018 6:02 PM

Yes, depending on whether the application is Physics, or in mechanical machinery, it should in inch-ounces or ounce-inches, not necessarily in that order...

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#6
In reply to #3

Re: Torque Calc,

03/26/2018 11:52 PM

Seems trivial, but is soooo important!

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harley
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#8
In reply to #3

Re: Torque Calc,

03/27/2018 7:44 AM

Torque is force times distance. Distance times force is the units for work.
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#10
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Re: Torque Calc,

03/27/2018 9:55 AM

Yes, they have the same units. The reason is that force and distance are both defined as 3-dimensional vectors. There are two kinds of 3-dimensional vector multiplications, cross product and dot product.

The cross product is used for calculating torque. The cross product of two vectors is a third vector perpendicular to the plane defined by the two vectors. Its length is the product of the lengths of the two times the sine of the angle between them. It can be visualized as the area of a parallelogram defined by the vectors as shown below. It is only defined for vectors of 3 dimensions.

The dot product is used for calculating work. The dot product of two vectors is a scalar value equal to the products of their lengths times the cosine of the angle between them. It can be visualized as the length of the projection of one of the vectors on the other as shown below. The dot product is defined for vectors or any dimension.

https://en.wikipedia.org/wiki/Multiplication_of_vectors

https://slehar.wordpress.com/2014/03/18/clifford-algebra-a-visual-introduction/
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#17
In reply to #10

Re: Torque Calc,

03/28/2018 6:35 AM

Sorry, missed that before I posted #15!

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KB0RAE
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#13
In reply to #8

Re: Torque Calc,

03/27/2018 2:48 PM

But it is not the same thing to have one pound hanging from a four foot rod vs a four pound weight hanging from a one foot rod? I was raised saying "Set the wrench to 100 foot pounds", not "Set the wrench to 100 pound feet". Does it really make a difference?
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#14
In reply to #13

Re: Torque Calc,

03/27/2018 11:46 PM

Wow! That's a BIG torque wrench, whether it is 100 lb-ft or 100 ft-lb, at least by my experience...

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harley
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#18
In reply to #13

Re: Torque Calc,

03/28/2018 7:38 AM

It makes no difference as long as everyone understands what you are talking about. In the USA, we almost always call it length times force even though that is technically incorrect for torque. We all know what we are talking about so it doesn't really matter.
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#15
In reply to #8

Re: Torque Calc,

03/28/2018 4:49 AM

In vectors, torque is a cross-product, a vector, work is a dot- product, a scalar. I'm pretty sure they both commute (definitely in the case of dot-product) so order of inputs doesn't affect it.

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#4

Re: Torque Calc,

03/26/2018 4:25 PM

http://www.calculatoredge.com/new/torque.htm

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MR. Guest
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#12
In reply to #4

Re: Torque Calc,

03/27/2018 11:32 AM

Good Link. GA from me...

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#7

Re: Torque Calculation

03/27/2018 4:41 AM

It's the "/" in "oz/in" that is the fly in the ointment.
It's ounce inches not ounces "per" inch.
BUT the arithmetic is correct... just multiply one by t'other.
Del

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#9

Re: Torque Calculation

03/27/2018 8:26 AM

Thanks Everyone.

I guess the old brain ain't dead yet.

Joe
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Codemaster (3); dkwarner (1); harley (2); IdeaSmith (1); KB0RAE (1); MR. Guest (2); NSS (1); PWSlack (1); Rixter (3); SolarEagle (1); user-deleted-1105 (2)

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