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DeWitt Harrison writes:
>Please consider the following experiment and then come to
>your own conclusions. Connect a torque wrench adapter
>to a torque wrench keeping everything in a nice straight line.
>Now apply, for example, an effort of 100 lbs-force at a
>distance of 3 feet from the bolt. I haven't told you any-
>thing about wrench or adapter lengths or what the torque
>wrench reads. Questions:
> a. How many foot-lb of torque moment does the bolt
> b. Does the bolt care what the torque wrench reads?
Does the adapter care what the torque wrench reads? Well, Mr. Bentley and
Mr. Audi seem to think so. At this point, I think it appropriate to point
out that the spec calls for a certain torque, applied with whatever torque
wrench, at the input point of the adapter. This will cause a fixed, orderly
amount of torque/force at the bolt, regardless of the length, breadth, or
price of torque wrench. A properly designed wrench will display correctly
the amount of torque applied at the output point, regardless of hand
position, pipes stuck in the end, etc. (Been there, done & tested that - in
a torque calibration facility). The sole exception to this is the
deflecting beam type, which has a pivoting hand hold, so that all of the
force is applied at one fixed distance from the output point.
Torque is not magic. As you state, bolts don't care. X force times Y
distance equals Z torque. The problem comes in with some misconceptions
about adapters. For a given length adapter, and a given torque at a certain
point on that adapter, the final torque at our uncaring, but
soon-to-be-tighter bolt will be the same.
BTW, if you really wanna get confused, think about the effects of
multipliers, and adapters/crow's feet at angles to the torque wrench...math
gets ugly quick...
>Now start changing the lengths of the wrench and adapter
>(using your infinite tool box)
Yup, need one of these...
Hope I haven't muddied the waters again...
87 4kcsq alpine white/light grey cloth
Member #47 NW Region AQC