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Re: 5 cyl timing belt questions

In message <199902192337.QAA21485@aztek-eng.com> DeWitt Harrison writes:

>   Let Tw = torque wrench setting/reading
>         T = torque actually applied to bolt
>         Lw = length of torque wrench (drive to point of force application or
>                       approximately the center of the hand grip)
>         Lx = length of extension
>   Then T = Tw (Lx + Lw) / Lw      or        T = Tw[1 + (Lx/Lw)].
> The use of the extension is less accurate since it depends on the
> "effective" length of the combination, i.e. it depends on how you
> hold the wrench. The wrench readout accurately measures the
> torque around the wrench's driver but, unfortunately and as much
> as we would like to believe otherwise, this torque is not related directly
> to the torque at the business end of the extension. The two torques
> are only related by the relative lengths of the moment arms.

As I've pointed out before, the Sykes Pickavant 1000Nm torque wrench
that I use for these things is actually a pre-assembled wrench and
multiplier combination - it breaks in the middle.  The instructions
go on at length about it being "vitally important that the wrench
is held in the centre of the handle - placement of the hand affects
the actual torque delivered."   Of course, the actual length of the
torque wrench has little to do with the issue; it's the effective
length - separation between force (hand) and fulcrum.

 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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