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02-14-2012, 09:16 PM
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Join Date: Jan 2007
Location: AOTP
Posts: 192
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Quote:
Originally Posted by L.Adamson
It's going to release at the setting it's set to...........which is based on one pound at one foot, for ft/lb settings.
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The spring will release when the torque *at the wrench head* reaches the value you have set (assuming the wrench is calibrated). This will be will be consistent regardless of the extension you have attached as long as the setting does not change. The torque at the wrench head will equal the force you've applied times the distance from the point of application of that force to the wrench head.
The torque at the end of the extension, however, doesn't simply scale as a function of torque and distance, it's a function of *force* and distance, the force being the force you've applied and the distance being the distance from the point of application of the force to the end of the extension. It does not matter that the torque in/on the system somewhere in between (say, at the wrench head) is less, the torque at the extension end is a function of total distance (wrench plus extension) times force applied.
__________________
Nauga
2004 RV-4
Last edited by nauga : 02-14-2012 at 09:19 PM.
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02-14-2012, 09:27 PM
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Join Date: Jul 2007
Location: Warwickshire UK
Posts: 703
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The torque on the nut is not being applied at the drive end of the torque wrench. It is being applied by the force on the handle.
If you applied a pure torque to the drive adaptor in the prop wrench (e.g. by using a pneumatic nut driver) you actually wouldn't apply any torque at the nut end of the prop wrench. (Imagine putting a screwdriver handle in the drive hole; it wouldn't matter how long the wrench was, you would just generate a linear force at the other end, not a torque)
I think this debate is a bit like the aircraft on a conveyor belt saga.
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02-14-2012, 09:34 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by nauga
The spring will release when the torque *at the wrench head* reaches the value you have set (assuming the wrench is calibrated). This will be will be consistent regardless of the extension you have attached as long as the setting does not change. The torque at the wrench head will equal the force you've applied times the distance from the point of application of that force to the wrench head.
The torque at the end of the extension, however, doesn't simply scale as a function of torque and distance, it's a function of *force* and distance, the force being the force you've applied and the distance being the distance from the point of application of the force to the end of the extension. It does not matter that the torque in/on the system somewhere in between (say, at the wrench head) is less, the torque at the extension end is a function of total distance (wrench plus extension) times force applied.
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I appreciate the long explanation, but the "spring" has perhaps already clicked........before your potential force and distance ever got there.
Your correct about force and distance in relation to absolute torque. But it has nothing to do with the spring setting. The spring only cares about the correct torque applied to the nut. Not the potential torque that you can add to it, by the force of leverage.
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02-14-2012, 09:40 PM
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Join Date: Jan 2007
Location: AOTP
Posts: 192
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Quote:
Originally Posted by L.Adamson
The spring only cares about the correct torque applied to the nut.
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No, the spring responds to, and is calibrated to, the torque at the wrench head. The torque is different at any other position in the system and is only a function of force and distance from that force to the point in question.
__________________
Nauga
2004 RV-4
Last edited by nauga : 02-14-2012 at 10:18 PM.
Reason: eliminated redundent redundencies :)
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02-14-2012, 10:05 PM
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fugio ergo sum
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Join Date: Apr 2006
Location: Carlsbad, NM
Posts: 1,912
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This would be a really nice place for someone with the proper equipment to set up a demonstration. Easier to do here than with "the downwind turn."
__________________
Larry Pardue
Carlsbad, NM
RV-6 N441LP Flying
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02-15-2012, 05:46 AM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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The formulas that all of you are getting stuck on are only for simple levers and pivots.
Torque wrenches when you include the indicating mechanizm are complex machines not simple levers.
The key is the calibrated indicating method of the torque being applied. If you take a typical high quality aircraft torque wrench and set it to click at 100ft pounds and pull it on a nut in stock configuration, it should click when there is 100ft pounds on the nut. How much you have to pull is based on how long the wrench handle is. Remember the clicker is calibrated to a certain torque on the nut driver shaft.
Now take the same wrench and add a 3 ft extension to the handle. Pull the handle till the clicker clicks.....You still get 100ft pounds at the nut as long as you stop pulling when the clicker clicks. The amount you have to pull is reduced because of the longer handle. The calibrated clicker still clicks at 100ft lbs at the nut driver shaft.
If you take all the indicating mechanizms away and use a spring scale on the end of a simple lever, all of these textbook formulas work just fine with including the lever length.
Last edited by Brantel : 02-15-2012 at 05:49 AM.
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02-15-2012, 05:55 AM
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Join Date: Aug 2006
Location: Johnson City TN
Posts: 196
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Well said Brian...
"If you take all the indicating mechanizms away and use a spring scale on the end of a simple lever, all of these textbook formulas work just fine with including the lever length."
I will add that if the attachment was welded on to the torque wrench then the over-all length would matter but it is not, the torque is all measured and applied to the attachmnet at a point 3 inches from the nut and this gives the additional leverage that must be compensated for.....
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02-15-2012, 06:47 AM
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Join Date: Aug 2005
Location: Grass Lake, MI
Posts: 128
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Not to ruin the fun, but I think it's way past time for the moderators to move this out of the classifieds section. I asked a question last week (on page 2) as to whether this works on a MT prop and there was so much talk about how to torque a prop that no one answered my question that could actually turn into a sale....
We are on page 11 now, and nothing in the last 8 pages has anything to do with the classifieds. Let's move this to the proper list.
And I'm still hoping someone can answer my question on whether this works on an MT 3 bladed RV-10 prop? The web site mentions Hartzell....
Thanks
-Mike Kraus
RV-10 Flying
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02-15-2012, 06:56 AM
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been here awhile
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Quote:
Originally Posted by mkraus01
Not to ruin the fun, but I think it's way past time for the moderators to move this out of the classifieds section. I asked a question last week (on page 2) as to whether this works on a MT prop and there was so much talk about how to torque a prop that no one answered my question that could actually turn into a sale....
We are on page 11 now, and nothing in the last 8 pages has anything to do with the classifieds. Let's move this to the proper list.
And I'm still hoping someone can answer my question on whether this works on an MT 3 bladed RV-10 prop? The web site mentions Hartzell....
Thanks
-Mike Kraus
RV-10 Flying
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Nawwww, let's leave it in classifieds so it will be deleted in a couple of weeks. 
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02-15-2012, 07:08 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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Quote:
Originally Posted by Brantel
The formulas that all of you are getting stuck on are only for simple levers and pivots.
If you take all the indicating mechanizms away and use a spring scale on the end of a simple lever, all of these textbook formulas work just fine with including the lever length.
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I guess Hartzell in wrong too... have a look at page 3-6 of the Hartzell manual.
http://www.hartzellprop.com/public_dl.php?id=4
Again, the .8 factor is ONLY for a 1 ft torque wrench, for any other length you need to do the math for your wrench.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Last edited by Walt : 02-15-2012 at 07:16 AM.
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