Funny torque tricks

[santoli9 at cox.net]

The length of the extender matters unless it is perpendicular to the wrench. The reason is that the force you are appliing to the wrench is also being applied to the extender. So you add that resulting torque to the torque applied by the wrench. The reason the formula has the length of the torque wrench in it is to calculate what force you are appliing to obtain the measured torque.
In otherwards: The length of the torque wrench is not relevant to the measured torque. If you could indipendently state how much force you were appliing to the torque wrench, you could multiply that by the lenghth of the extender and add it to the measured torque, getting the same result as the formula provides (assuming the extender is in-line with the wrench otherwise multiply by the cosine of the angle). This is not complex physics, it's simple algebra.
Or to add more manure to the heap:
If the torque wrench is 3 feet long and you measure 300 foot-lbs, then you applied 100 lbs of force. A 1 foot extender would then add another 100 ft-lbs giving a total of 400 ft-lbs. Put another 3 feet on the wrench (making it 6 feet long), and you will only need to apply 50 lbs force to get 300 ft-lbs. a 1 foot extender will then add 50 ft-lbs resulting in a total of only 350 ft-lbs. If the torque wrench were 1 foot long you would apply 300 lbs to get 300 ft-lbs, a 1 foot extension would add 300 ft-lbs for a total of 600 ft-lbs. If the extender were 2 feet long and the wrench 1 foot long the total would be 900 ft-lbs. If a 1 foot extender were at a 45 degree angle to the 3 foot wrench the total would be 300 + 100 * cos  45 or 370 ft-lbs. If the earth were rotating backwards...........
Steve (Mechanical Engineer with an atitude)

The an
> 
> From: "Al Powell" <apowell at gocougs.wsu.edu>
> Date: 2003/12/03 Wed AM 11:05:19 EST
> To: <quattro at audifans.com>
> Subject: Funny torque tricks
> 
> SJ said:
> 
> [As Ameer pointed out, everyone got it right about the tool, and the use of
> different extensions, and the basic torque formula. The difficulty was that
> we did not realize how important the torque wrench length was to the
> discussion.....]
> 
> I guess I'm the holdout.  I've saved SJ's lengthy explanation for review
> since I'm running out the door for a biz trip...however, the statement above
> and his whole argument just don't make any sense to me.
> 
> All my common sense and logic tells me that if you apply 100 lbs/ft to a
> point of turn (including the famous tool 2079), it doesn't make any
> difference whether the wrench used is 1 foot long or 100 ft. long. 100
> lbs/ft is the same amount of force regardless of the length of the tool used
> to apply it....so it does not matter.
> 
> If SJ's statement about length of the wrench were true, then Audi would have
> specified NOT ONLY the tool 2079, but would ALSO have specified the precise
> length of the torque wrench used to apply the torque.  They did not.  Hence,
> in Audi's eyes, the length of the torque wrench is immaterial. Audi is anal
> enough that if it mattered, they would have specified the length of the
> wrench to be used.
> 
> Therefore I (respectfully, to avoid hurting anyone's feelings) cannot agree
> with SJ's conclusion.
> 
> ************************************
> Al Powell
> apowell at gocougs.wsu.edu
> 1958 Fiat 1200 Transformabile Spyder
> 1983 Datsun 280ZX Turbo
> 1993 Audi 90Q
> 1997 Chebby Blazer
> 1999 Chebby Blazer
> ************************************
> 
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