Chris Amley asks:
> So if someone could describe cowl or scuttle shake, I'd be able to see
> how the description matches with my experience.
I always understood cowl or scuttle shake to refer to a dashboard that
squeaks and rattles as a consequence of poor tortional rigidity of a car.
Imagine grasping the front and back of your car and wringing it out like
you wring out a wet rag. Tortional stiffness is the resistence to this sort
of twisting. Convertibles tend to twist significantly more than hard-tops
because they lack the stiffness that a roof would otherwise provide.
Imagine trying to twist a flat piece of cardboard vs. a cardboard box; the
box is much stiffer. A convertible is more like the flat piece of
cardboard, because only the floor section in the middle of the car resists
twisting, while a sedan is more like the box, because the floor, roof, and
pillars form a box section. The dashboard (scuttle, cowl...), however, is a
stiff assembly that's bolted across the most flexible portion of a
convertible. So as the convertible body flops around like a rag doll, this
stiff dash assembly squeaks and rattles in its mounting bolts.
> The front suspension is in good shape (although the dampers have some
mileage
> on them), the wheels are true and balanced, and I just replaced the rear
axle
> bearings (lot of that going on these days).
None the less, I suspect that you have an imbalance somewhere. It could be
in the engine itself (bad engine mounts would exaggerate its tendency to set
up oscillations elsewhere in the car), prop-shaft, a trasmission that is
becoming unbolted from the engine, poor wheel alignment... Any number of
things.
So, yes, you most certainly have scuttle shake. But--short of welding in a
full roll cage from the rear suspension mounts to the front--you'll never
get rid of it, and the scuttle's not the source of the problem.
Kevin Riggs
'72 TR6
rkriggs@ingr.com
Huntsville, AL
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