> ------------------------------
> Date: Thu, 14 Apr 94 14:08:31 PDT
> From: toms@sharebase.com (Tom Sabo)
> Subject: Torque wrenches & extensions.
> On a theoretical level, the socket extension can act as a torsion bar,
> reducing the torque getting through to the head of the nut or bolt.
> I don't think this makes much of a difference for a normal sized extension
> (which to me means 3/8" drive by 6-7 inches long). Anybody have a
> table we could look this up on? Just curious...
> - --toms.
Ummm... NAAH!
Lets all go back to Statics 201. You have a rod. It is fixed at one
end to an unmovable object (the bolt). You apply a torque to one end.
Forces must balance in a static system. Therefore the same torque is
seen at all points of the system. The rod will deflect, but once it
reaches equilibrium, it will then transmit the same torque to the
bolt.
What changes this is:
1. If you don't hold the torque wrench normal to the head of the
bolt. In this case some of the torque is transmitted off axis,
showing a higher torque than actually applied. This is easier to do
with an extension. Corollary-Never use a universal joint coupling with
a torque wrench.
2. Using a lateral extension which would change the lever arm.
This would also lead to lower torque than indicated. The thingies I
have seen which do this look like an open end wrench with a socket
drive point in the handle section: (please excuse the asciigraph)
________
/ \_______
/_____ _____ |
\ | | |
______/ |___| |
\ _______|
\________/
3. You are applying a counter torque by holding the shaft or head of
the torque wrench. Also more likely to happen when using an
extension. Will also apply a lower torque than indicated.
Makes sense??
Steve Pozar:
> As someone already has said, most of us can relate to this thread.
> My daily reminder of this "disease" is a cartoon of a big Healey,
> wire wheels removed, wooden blocks under the splines. The car
> is a 100-4 because the windshield is partially down. The owner is
> in the drivers seat with his eyes closed. There is an elecrtic fan
> sitting on the bonnet. The caption reads "Great Expectations"
For the last two weeks, my 19 month old son makes me take him out to
Maggie six times a day. He sits in the driver's seat and goes
"Roar,Roar" and then laughs like crazy. His dreams are much better
than mine for keeping the restoration going.
______________________________________________________________________
Jay Nemeth-Johannes 87 Merkur XR4ti
Hewlett-Packard 83 VW GTI
VXI Systems Division 71 Saab Sonett
Loveland, Colorado 58 MG ZB Magnette
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