Torque Wrench adapters...

[christopher_bender@fmc.com (CHRISTOPHER BENDER)]

     I've been listening to a lot of talk about this subject recently, and 
     so far only one guy has got it right.  I forget his name, but he 
     concluded his proof with "Q.E.D.," which stood out to me, because my 
     favorite math professor used that all the time.   The latest post has 
     it totally wrong.  A guy claiming to be a mechanical engineer tells us 
     that the torque calculation has nothing to do with the length of the 
     torque wrench.  Hello?!?  This is simple statics!  How long ago did 
     you have the course???  Well, I'm getting fed up with the ignorance, 
     and I am gonna take a stab at it.
     
     It's real simple.  Torque varies linearly in a cantilever beam.  A 
     wrench is just that: a cantilever beam.  Torque is theoretically 
     maximum at the base (the fastener being torqued) and is zero at the 
     point of application (The end of the wrench that you push, pull, stand 
     on, etc.).  It varies linearly between the two ends for any point of 
     interest in between.  So, when you use an extension, you have to scale 
     up the torque LINEARLY by the ratio of the total length (wrench plus 
     extension) to the length of the wrench alone.
     
     But what does this mean to us Audi people trying to use tool 2079?  
     Well, it means, that the torque specification given by Mr. Bentley is 
     conceptually flawed.  To specify a torque of 258 lb-ft with tool 2079, 
     but without specifying the torque wrench to be used, is wrong because 
     they have to make an assumption of the length of your torque wrench.  
     
     This is in theory though, but how much does it really matter?  Most 
     torque wrenches capable of reading 258 lb-ft are somewhere between 18" 
     and 24".  Let's assume tool 2079 has a center to center distance of 
     12" (I actually own that tool, and that sounds about right, although I 
     haven't measured it.)  If we do the math for each of the extremes, an 
     18" torque wrench would give a torque at the bolt of 430 lb-ft, and a 
     24" torque wrench would give 387 lb-ft.  That's about a 10% 
     difference, which really shouldn't matter much.  So, in practice, if 
     you torque that mother to around 400 lb-ft, you should have no 
     trouble.  Q.E.D. that!!
     
     I'm sorry if I'm sounding rude, and I hope you all will keep the 
     flamage to a minimum, but I have just been hearing way too much on 
     this relatively simply subject, and I am getting tired of it.
     
     Happy Torquing..
     
     Chris