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  #211  
Old 02-16-2012, 07:47 PM
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PerfTech PerfTech is offline
 
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Default Size doesn't matter

In this exercise, and possibly only this one! The size of your tool means absolutely nothing. It's all in the size of my tool and the way you use it.
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  #212  
Old 02-16-2012, 07:59 PM
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I think it's time for a poll

By the way, I find it very interesting that the issue of torque wrench extension correction factor turned out to be so controversial, like primer or no primer, tailwheel vs. nosewheel, tipup vs. slider, etc., because in this case there IS only ONE truly correct answer and it can be (and has been) PROVEN mathematically.

This is not rocket science, but at least one rocket scientist, scsmith, along with many, many other very informed individuals have weighed in with the correct answer. The correction factor is NOT constant, but dependant on the length of your torque wrench (as measured from the center of the socket stud to the center of the handle), the length of the extension, and the angle of the extension.

If you are torquing your prop bolts with this tool or any other torque wrench extension tool (Avery's, Hartzell's, crow's foot, etc.), ALWAYS follow the instructions in AC-43.13 and the torque values for your propeller.
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Last edited by Sparky : 02-16-2012 at 10:29 PM.
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  #213  
Old 02-16-2012, 10:25 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Quote:
Originally Posted by PerfTech View Post
...This discussion has been absolutely wonderful for us and since Sunday PM we have sold all but nine from our first run of 400 wrenches. Thank you to everyone for your support...
Allan, your explanation is still invalid, your math is still wrong, and the torque values that follow from them are dangerously under-spec for any torque wrench with a handle longer than about 18". Several engineers, both mechanical and aeronautic, have clearly explained why that is so.

The fact that you so cavalierly exploit the controversy you have stirred up here to increase sales suggests that you do not have your customers' best interests at heart. I hope that that is not actually the case.

Thanks, Bob K.
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  #214  
Old 02-16-2012, 11:56 PM
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PerfTech PerfTech is offline
 
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Quote:
Originally Posted by Bob Kuykendall View Post
Allan, your explanation is still invalid, your math is still wrong, and the torque values that follow from them are dangerously under-spec for any torque wrench with a handle longer than about 18". Several engineers, both mechanical and aeronautic, have clearly explained why that is so.

The fact that you so cavalierly exploit the controversy you have stirred up here to increase sales suggests that you do not have your customers' best interests at heart. I hope that that is not actually the case.

Thanks, Bob K.
Bob; My explanation is absolutely valid, my math is perfect and the torque values that follow from them are spot on. I graduated top of my class at MIT with three degrees in mechanical engineering with specialties in stress analysis and metallurgy. I have over forty years experience in tool design, owned and operated Omega Tool Co. (A company with 6 m $ yearly revenue specializing in the development and manufacture of specialized aircraft tooling). Believe me when I say, "I do not make mistakes with Jr High math". As for your accusation that I have somehow stirred up a controversy, down rite ridiculous! I posted a top of the line product at a very low price with clear, concise instruction in it's use. The controversy was generated by the very small camp that has a problem understanding this simple mechanical concept. They passed their confusion on to others who truly wish to understand. I will rectify this misconception early next week when I return from my business trip on Tuesday the 21st. Keep an eye out for the video as it will be very entertaining as well as informative. Thanks,Allan
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  #215  
Old 02-17-2012, 12:00 AM
CMW CMW is offline
 
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Default Two More Videos

Okay, Here are 2 more videos that hopefully show once and for all that statics works and that the equation Wrench Torque = Bolt Torque (wrench length) / (wrench length + crows foot length) is correct. All I had was a 1 inch crows foot with a 1.5 inch offset. The clicker torque wrench is 12 inches and the cheater is 20 inches.

I'm no Allan when it comes to making videos. Sorry about the volume (turn it all the way up). The Drift HD mic didn't pic up my voice very well. Turn down the volume before the video ends because there is a nasty beep at the end of each video.

http://www.youtube.com/watch?v=sdDNY...eature=channel

http://www.youtube.com/watch?v=nNjye...eature=channel
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  #216  
Old 02-17-2012, 06:01 AM
Birkelbach Birkelbach is offline
 
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Quote:
Originally Posted by PerfTech View Post
Bob; My explanation is absolutely valid, my math is perfect and the torque values that follow from them are spot on. I graduated top of my class at MIT with three degrees in mechanical engineering with specialties in stress analysis and metallurgy. I have over forty years experience in tool design, owned and operated Omega Tool Co. (A company with 6 m $ yearly revenue specializing in the development and manufacture of specialized aircraft tooling). Believe me when I say, "I do not make mistakes with Jr High math".
No one is arguing that your math is wrong. The problem is in one of your assumptions. Specifically, your claim that you can insert 12" arbitrarily into the equation simply because you are using ft -lbs as your unit of measure. If you convert YOUR math to the metric system with YOUR assumptions you will get a different multiplier, because you will be putting 100cm in place of your 12" (assuming you use N-m as your torque measurement) since 100cm = 1m.

Quote:
As for your accusation that I have somehow stirred up a controversy, down rite ridiculous! I posted a top of the line product at a very low price with clear, concise instruction in it's use. The controversy was generated by the very small camp that has a problem understanding this simple mechanical concept. They passed their confusion on to others who truly wish to understand. I will rectify this misconception early next week when I return from my business trip on Tuesday the 21st. Keep an eye out for the video as it will be very entertaining as well as informative. Thanks,Allan
If this were in fact a primer war I'd have gotten out of it long ago. But this is prop torque. I don't want to read this in some NTSB report two years from now and know that there was 'something else' that I could have said.

Let's summarize ....

Side A claims that 0.8 is a constant multiplier that can be used to calculate the torque wrench setting with a three inch extension regardless of wrench length.

Side B claims that the torque wrench setting must be calculated with a formula that takes into account the length of the wrench.

Side A offers...
  • Some good high school math.
  • Credentials of the original presenter.
Side B offers...
  • Free body diagrams
  • Some good high school math
  • Well established equations
  • Numerous citations including the FAA, propeller manufacturers, torque wrench manufacturers, a statics textbook and countless web pages with calculators.
  • Peer review
  • Video documented empirical tests of the formulas. (Well done Chris!!)
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Last edited by Birkelbach : 02-17-2012 at 06:37 AM.
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  #217  
Old 02-17-2012, 07:48 AM
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Default Multiplier .8

...We are not trying to re-design some manufacturers already built torque wrench with a cheater bar. If one desires a longer tool then buy one. What I said was "If you are using a foot pound torque wrench .8 is the multiplier with our tool". Regardless of your having a 12", 18.77", 23.842" 31" or a 99" or any other length commercially manufactured foot pound torque wrench. When set to 100 ft lb they will all read, click bark or chirp at the same time when the same. If you want 100 ft lb with our prop wrench in the mix you will need to set them all at 80 ft lb. to get your desired 100 ft lb. The videos posted verify this exactly. I'm not manufacturing cheater bars, nor advocating their use, we are making a very high quality torque adapter that will perform flawlessly used as directed. Thanks, Allan
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Last edited by PerfTech : 02-17-2012 at 07:56 AM.
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  #218  
Old 02-17-2012, 07:57 AM
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Brantel Brantel is offline
 
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Somebody please get Chris a different length torque wrench so he can redo the experiment.

Don't worry Chris, the Myth Busters sometime have to go back and do more test after the fact due to feedback.

I for one can't wait to see how this turns out!
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  #219  
Old 02-17-2012, 08:01 AM
Birkelbach Birkelbach is offline
 
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Quote:
Originally Posted by PerfTech View Post
...We are not trying to re-design some manufacturers already built torque wrench with a cheater bar. If one desires a longer tool then buy one. What I said was "If you are using a foot pound torque wrench .8 is the multiplier with our tool". Regardless of your having a 12", 18.77", 23.842" 31" or a 99" or any other length commercially manufactured foot pound torque wrench at 100 ft lb they will all read, click bark or chirp at the same time when set to 100 ft lb.
Agreed. This is simple, high school physics. Nobody is arguing this. Even with the cheater bar this is generally the case.

Quote:
If you want 100 ft lb with our prop wrench in the mix you will need to set them all at 80 ft lb. to get your desired 100 ft lb. The videos posted verify this exactly. I'm not manufacturing cheater bars, nor advocating their use, we are making a very high quality torque adapter that will perform flawlessly used as directed. Thanks, Allan
Do not agree. The video that Chris did clearly shows that if you are not using the offset distance then the cheater bar does not matter. Once you add the extension the cheater bar does matter. Watch the videos again. At the end of the second video Chris had to readjust his torque wrench setting to get the SAME torque on the bolt with his cheater bar. How is adding the cheater bar different than using a longer wrench?

PLEASE, PLEASE, PLEASE sit down with an open mind and write this out for yourself. I agreed with you 200+ posts ago but before I weighed in, I did the math myself, on paper with no assumptions using different lengths and forces. It took me less than 10 minutes to convince myself that my initial intuition was wrong.
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Last edited by Birkelbach : 02-17-2012 at 08:04 AM.
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  #220  
Old 02-17-2012, 08:10 AM
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JonJay JonJay is offline
 
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This argument is simple. You either agree that a clicker type torque wrench follows the same physics as a beam type or you don't. They are certainly built differently.
The video didn't help. Adding a cheater to a 12" wrench doesn't make it a longer clicker wrench. I would like to see the same experiment done as a comparison between two clicker wrenches of different lengths. That would answer the question.
Again, I am really glad the clicker wrench I use is 12" to the center of the grip!
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