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Torque Wrench adapters...

In message <199702261510.AA01889@igw.fmc.com> christopher_bender@fmc.com (CHRISTOPHER BENDER) writes:

>      I've been listening to a lot of talk about this subject recently, and
>      so far only one guy has got it right.

Two, actually.  One being me.

>      I forget his name, but he concluded his proof with "Q.E.D.," ...

See below.

>      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.

And get it wrong ...

>      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.

Wrong so far, but carry on.

>      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.

No.  Mr Bentley is not actually the source for this information - it's Mr
I quote from "Reparaturleitfaden Audi quattro 5-Zyl. Einspritzmotor", Audi 
publication number 000.5148.29.00, Reparaturgruppe 13, Absatz 13-6:
       "Anzugsdrehmoment 350Nm mit Sonderwerkzeug 2079 und 2084
        Anzugsdrehmoment 450Nm ohne Sonderwerkzeug 2079"
350Nm is 258 lb ft, and 450Nm is 332 lb ft.  Now - I don't personally care a 
flying **** _HOW_ Audi reached these values - but both are documented for
the I5 engine.  400 lb ft is 20% over-torque, assuming that your torque wrench 
is accurate. 

>      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.

Me too, especially from amateur applied mathematicians.

Oh, and Q.E.D.  

 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club