Date:         Wed, 21 Mar 2001 10:14:27 EST
Reply-To:     JKrevnov@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rico Sapolich <JKrevnov@AOL.COM>
Subject:      Re: Heater Mtr. Replacement & Those Damn Shear Bolts
Content-Type: text/plain; charset="US-ASCII"

Oh the power of the Urban Myth.  I do not know why VW or Volvo uses shear
head fasteners to mount their steering columns.  I speculate that it is to
assure that at least a calculated minimum torque is applied to these
fasteners during the production assembly process.  I offer this opinion for
two reasons:

1) No self-respecting thief is going to muck around with dismantling the
steering column in order to make off with such a sought after bit of
automotive exotica.  He is there to steal a car, not while away his time.

2) Some time ago, a friend of mine was a green engineer in the R&D department
of DeLaval Turbine.  One of his first assignments was to come up with
procedures in order to accurately torque the sundry fasteners in their
assemblies.  After much investigation, he found that, considering all the
variables, the applied torque could vary as much as +/- 20% from the target
value.  He concluded that the only way to predictably tighten fasteners was
to measure bolt stretch.  If you consider attitude of the average auto
assembly line worker, that might explain why VW chose to use torque-to-shear
heads on a component which would cause some inconvenience if it should come
loose.

Rich