Torque Wrenches - my answer...

[Huw Powell]

> This is the fundamental problem right here.  One camp sees this as a 
> simple lever arm lengthening, whilst noting that there is a potential 
> pivot point that has no bearing on the problem.  The other camp is 
> trying to complicate the problem by thinking too hard about the pivot 
> point.

Well put...

>> Picture the microcosm of the meeting point between the two tools, if 
>> you  will.  At that junction, there is a square hunk of metal, the 
>> driving nub thing of the torque wrench, that is imparting a twisting 
>> action to the 2079.  Each of the four faces of the "nub" are pushing 
>> in different directions, 90 degrees to each other, but all 
>> perpendicular to a radius drawn from the center of the nub.
> 
> True but pointless to the problem.

Please, why is that?  Is it because at the moment in time that 
everything matters, there is no motion about that point?

A good reason to ignore the junction is all that I need, not just a 
desire to ignore it.

Having not used the tool in question (has anyone discussing this besides 
Phil even *seen* one?), I haven't had the opportunity to observe whether 
the pivot acts "rigid" at the point of interest, the 258 ft-lb "click" 
of the wrench.  Whatever I suspect or think is as irrelevant as anyone 
else's thoughts on the matter.

I can see that if the two tools were moving in unison at that time, ie, 
staying in a nice straight line, then all the lever arm length math 
would apply quite simply.

>> In terms of its internal stresses, the 2079 is more like a chain drive 
>> with a pair of equal diameter gears at each end, moving the torque 
>> from its source to the fixed point at its other end.
> 
> This is fantasy.

And that is bordering on rude.

>> Another mental picture that is useful...

> No, torque can always be translated back to a force on a lever.  The air 
> impact wrench example is specious, as is much of the discussion on this 
> matter.

Well, please accept my apology for errant speciousness.

>> So, does anyone up here in snowy (!) New England have a 2079 kicking 
>> around so I can play at some experiments and prove myself right or 
>> wrong? (at least to my satisfaction...)
>>
> Please someone :-)

Don't act so exasperated.  This is a problem that can be easily tested 
on the bench, if and when I have done so, I will report fully without 
prejudice.  I would prefer to apply my torque to a spring of some sort, 
so the results can be photographed, but I doubt if I can rig that up.

If these wandering threads bother you, by the way, the easiest way to 
take them is to delete and ignore them...

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/