Torque: Kicking the shot engineer

[Robert Mangas]

  Alan, that was a thought experiment outlined below; as such, all wrenches 
are perpetually in perfect calibration.  It all works out just fine if you 
do the math; the length of the torque wrench used to apply the torque to the 
VAG extender is shown by this example to have an effect on the nut holding 
on the crank pulley.

>From: Alan Pritchard <apritchard at seaeye.com>
>To: quattro at audifans.com
>Subject: RE: Torque:  Kicking the shot engineer
>Date: Thu, 4 Dec 2003 15:09:45 -0000
>
>
>Ok, let me get this straight, it appears you changed torque wrenches at 
>step
>7 (to a 4' wrench), and this is where it stopped working out??? That's how 
>I
>am interpreting your process. Torque wrenches are only accurate if they are
>regularly calibrated, and even then they have a tolerance (say 10%) so your
>two torque wrenches could easily be far enough out, for your maths not to
>work out. If I'm misinterpreting then I apologise.
>  -----Original Message-----
>From: 	Robert Mangas [mailto:porter_t_dog at hotmail.com]
>Sent:	04 December 2003 15:00
>To:	munrof at sympatico.ca; quattro at audifans.com
>Subject:	Torque:  Kicking the shot engineer
>
>
>    My name is Robert and I was a Disbeliever.  Then I ran my garage
>experiment to confirm that the extender is a torque multiplier.  At that
>point I still believed that the length of the torque wrench was irrelevant
>as long as the torque applied to the extension was held constant.
>
>   Just for giggles, I arbitrarily changed the length of my torque wrench 
>in
>my figuring and re-solved for the torque applied at the bolt (torque at the
>torque wrench/extender joint held constant).  It changed.  The math is
>simple.  Run the excercise and there is no arguing with the conclusion; my
>intuition let me down, and while humbling that's always instructive.
>
>    For me, the easiest way to consider it is this:
>
>1.  Set the applied torque as read on the torque wrench. For ease say 100 
>lb
>
>ft.
>
>2.  Set the torque wrench length.  For ease say 2'.
>
>3.  Determine force applied to wrench.  100 lb ft/2 ft=50 lb.
>
>4.  Determine force at nut with extender.  50 lb x 3' (2' wrench + 1'
>extender)=150 lb ft.
>
>5.  Change length of torque wrench.  For ease say 4'.
>
>6.  Repeat step 3; 100 lb ft/4ft=25 lb.
>
>7.  Repeat step 4; 25 lb * 5' (4' wrench + 1' extender)=125 lb ft.
>
>8.  Compare the results of step 7 and step 4.  Does 125 ft lb = 150 ft lb?
>It does not, therefore we must conclude that the lenght of the torque 
>wrench
>
>does have an effect on the torque applied to the bolt.
>
>   Like some others have also stated, it took actually going through the 
>math
>
>for me to get it.
>
> >From: "Fred Munro" <munrof at sympatico.ca>
>
>
> >
> >It doesn't matter whether you use a 6 inch torque wrench and 516 lbs on 
>the
> >handle or a 4 foot wrench and 64.5 lbs on the handle - if both are
> >connected
> >to the 2079 tool and click at 258 ft.lb, you'll be OK.
> >
> >IMHO anyway.
> >
> >Fred Munro
>
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