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  #271  
Old 02-18-2012, 06:32 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by sstellarv10 View Post
Wow Allan, you couldn't have asked for any better advertising than this thread has created.
That might be true, but only if you believe that "all exposure is good exposure".
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  #272  
Old 02-18-2012, 07:21 PM
BillL BillL is offline
 
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Default Scary

This thread has been kind of scary with all kinds of directions of the arguments and lack of mathematical rigor. Even that youtube video drove incorrect conclusions due to the poor conditions of the test. Care was not taken to ensure torque alone was transferred from the click wrench to the dial. You could see that from the bending.

I like the tool and knowing the offset is 3 inches is just fine when properly used for the torque wrench length one chooses.

The fundamental engineering principles to address this whole situation, should one want to pursue, is the concept of the free body diagram in statics. Sum forces in the x and y direction and moments about a common point.

Allen, considering all the confusion resulting here you should correct your video (re the .8 factor) so that the less informed will not end up with improper torque. All torque wrenches don't have a 12 inch moment arm, nor their users the benefit of the talent on VAF Forums.
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Lord Kelvin:
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and express it in numbers, you know something about it; but when you
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  #273  
Old 02-18-2012, 07:22 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
That might be true, but only if you believe that "all exposure is good exposure".
Exactly. All the time I've been contributing to this thread I was thinking of the DecorMyEyes debacle.

Thanks, Bob K.
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  #274  
Old 02-18-2012, 07:29 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Just in case we've forgotten what we're arguing about, I thought I'd quote this back here at the end of the thread, closer to where the latest discussion is.

Quote:
Originally Posted by PerfTech View Post
All foot lb. torque wrenches are the same regardless of handle overall length. The overall length only effects how hard you need to pull on it. on a foot lb. torque wrench the .8 multiplier is exactly and always the number. It is not rounded off and it never changes as long as the crows foot or our tool is 3" and in installed straight. If you install it on the torque wrench at 90 degrees the multiplier is 0, at a 45 degree angle it is .9. This is simple math and does not change.
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  #275  
Old 02-18-2012, 07:55 PM
RVnoob RVnoob is offline
 
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IT's Saturday night... it's enough torture for the week.
A few who are in the know are conspicuously absent. :-(



Quote:
Originally Posted by PCHunt View Post

The reason length doesn't matter is that the torque wrench is indicating the torque on the nut, and not the force on the end of the wrench.

A wrench handle can be any length, and if the torque reading is calibrated at the nut end of the wrench, it will tell you the torque on the nut, which is what you want.

So, wrench #1 is 10 feet long, with a dial that indicates ft-lbs (or more correctly lb-ft) at the NUT. if you want 100 pounds of torque, you would apply a force of 10 lbs at the handle, and the dial would read 100. (10 feet X 10 lbs = 100 ft-lbs)

Wrench #2 is 1 foot long, with a dial that reads torque at the NUT. If you want 100 lbs of torque, you would apply a force of 100 lbs at the HANDLE, and the dial would read 100. (1 foot X 100 lbs = 100 ft-lbs)

You guys are confusing the nut torque with the force needed at the handle.

All torque wrenches read TORQUE AT THE NUT, not force on the end of the handle.

That's why the length of the handle doesn't matter for torque wrenches.

Taking all bets!

Quote:
Originally Posted by PerfTech View Post

I will try this one more time. Forget the length of your wrench, Forget cheater bars and everything else. If you have a torque wrench that you currently use to torque things in foot lbs. and you want to torque a bolt to 100 foot lb. you set your wrench or reed your gauge at 100. If you use our prop wrench with your torque wrench and want 100 foot lbs. you set or read your torque wrench to 80 foot lbs. You do not need to do any math or calculations of any kind. We have done that for you. Allan


Quote:
Originally Posted by rv8guy View Post

The constant is the 3 inch extension. The torque is applied to it, not the nut.

Stimulating discussion

Quote:
Originally Posted by The Paintman View Post

And here we are back at what Allan said right at the beginning. He has done the math for us and in order to achieve the desired torque on the nut one would have to set the wrench at .8 of whatever ft-lbs you require. The reason is that the point of torque on the nut has been moved by 3'' which will always remain the same as long as you are using Allan's prop wrench. In other words the torque wrench will "click" at the correct torque setting regardless of the length of the handle. If however, you were using an ordinary flat or ring spanner and extended the handle it would be a very different story!!


Quote:
Originally Posted by erich weaver View Post

HEY! I get it now, thanks to a few of the posts above. When you set the torque wrench for 100 ft lbs, by definition, you are going to have a force of 100 lbs applied 1 foot from the end of the wrench regardless of how long your wrench is, so that's where the 12 inches comes from. When you add the 3 inch extension, you are applying that 100 lbs to the close end of the extension, but more than 100 lbs to the nut at the far end of the extension. Hence the multiplier of 12/(12 + 3) = 0.8

WOO HOO! Now I can sleep.

Erich

Last edited by RVnoob : 02-18-2012 at 08:16 PM.
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  #276  
Old 02-18-2012, 08:18 PM
BillL BillL is offline
 
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Default Still Missing the math . .

Sorry Bob, but although I don't know how to properly use quotes on this site, but I can do simple math and this quote below is simply wrong.

Here is the simple math - My torque wrench is 16 inches to the center. So that means put a force of 75 pounds of force to yield 100 ft-lbf. For the math that is 16*75/12=100. Now lets add the 3 inches. Now the moment arm is 19 inches (16+3=19) and the wrench is still set to 100 and I still pull with 75 pounds. Simple math: 19*75/12=118.75 ft-lb. Hmmm . . . . simply not .8. This "factor" is .8421. So the math does work and the statement below is not factual.


"Originally Posted by PerfTech
All foot lb. torque wrenches are the same regardless of handle overall length. The overall length only effects how hard you need to pull on it. on a foot lb. torque wrench the .8 multiplier is exactly and always the number. It is not rounded off and it never changes as long as the crows foot or our tool is 3" and in installed straight. If you install it on the torque wrench at 90 degrees the multiplier is 0, at a 45 degree angle it is .9. This is simple math and does not change."
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Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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  #277  
Old 02-18-2012, 09:01 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Quote:
Originally Posted by BillL View Post
Sorry Bob, but although I don't know how to properly use quotes on this site, but I can do simple math and this quote below is simply wrong...
Bill, I agree with you. Allan's math is still invalid. But not everyone here believes that yet, and some have lost track of what the central point of this thread is.

Thanks, Bob K.
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Last edited by Bob Kuykendall : 02-18-2012 at 09:05 PM.
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  #278  
Old 02-18-2012, 09:36 PM
CMW CMW is offline
 
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Quote:
Originally Posted by BillL View Post
...... Even that youtube video drove incorrect conclusions due to the poor conditions of the test. Care was not taken to ensure torque alone was transferred from the click wrench to the dial. You could see that from the bending.
Bill, I agree with you also. The .8 is not a constant and I think Allan should make that correction.

I also agree with you the the test conditions in the youtube video I made were not ideal, but they were good enough to show that the length of the wrench matters. The "bending" you see in the video is not actually bending, it is my welding table that the vise is attached to rocking. It looks like the dial wrench handle is bending because of the ultra wide angle lens on the camera. I can assure you it looks much worse in the video than in person.

I think that Bob and I and others have done way more than should have been necessary to try and explain through mathematical rigor, free body diagrams, moment diagrams and videos why an established and published equation for using a crows foot is correct.

Once again I ask the disbelievers what they would have done if Allan had not given any multiplication factor?
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  #279  
Old 02-18-2012, 09:53 PM
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PerfTech PerfTech is offline
 
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Default I am really going to enjoy this!!!!!!!!!!!!

See you soon. "TORQUE MAN" AKA, Allan
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  #280  
Old 02-18-2012, 10:02 PM
RVnoob RVnoob is offline
 
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.


Torque wrench is a measuring instrument,
it must be used at the handle.
You cannot grab the torque wrench at the middle of the shaft, or with a cheater bar.


.

Last edited by RVnoob : 02-18-2012 at 10:17 PM.
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