Torque Wrenches - my answer...

[Fifield, Douglas]

Hugh mused:

But there is no lever arm lengthening going on.  If the business end of 
the torque wrench were fixed solid to the 2079, there would be.  But 
it's not, it is a pivot point, with its axis fixed relative to each 
tool, upon which the torque wrench is acting.

snip>

Oh, but there is (lengthening going on).  Hugh, your points are good, but
IMHO, wrong.  When the torque wrench is inserted in the square hole at the
end of the 2079 tool, it has the same effect on the "force/torque" result
(at the bolt) as a length of pipe used as a cheater bar.  The bolt doesn't
know anything about the length of the moment arm.  All it sees is the
torque.  If we were able to see the little force lines emanating from the
moment arm, they would be greatest closest to the bolt and ramping down as
you move out toward the end of the moment arm.

So, if the spec'd torque on the crank bolt is 340 Ft-Lb, then the force line
one foot down the moment arm from the center of the bolt would equal 340
lbs. of force.  Two feet away, 170 lbs. force.  Four feet, 85 lbs. force,
etc.  When the torque wrench is connected to the 2079 tool and is set to 250
Ft-Lb (or whatever the spec is), it will click (or register proper torque
achieved) when 250 lbs of force are exerted one foot out along the moment
arm from the center of the torque wrenches square lug.  If you measure the
distance from that point to the center of the crank bolt and calculate the
torque applied by 250 lbs of force, you will find that it equals the 340
ft-lb of torque originally called for (or whatever the spec'd torque is -
I'm working from memory here, and as a child of the sixties, that is swampy
territory).

So, in essence, the torque wrench attached to the 2079 tool attempts to
apply torque, but the rotational force applied to the end of the 2079 tool
result in rotational movement, but with a radius equal to the distance
between the center of the torque lug and the center of the crank bolt.

HTH.

Douglas in MN (with a PE)
95.5 //S6Avant - mine
98 Mercury Mountaineer - her work sled
98 Toyota RAV4 - for sale
73 BMW R60/5 - lonely in the garage