Bob,
I suspect that 'shakes' has different meanings to different people.
To me, it's the rattle-rattle-rattle, or the bump-bump-bump that you were
describing before. It's a repetitive event.
By that definition, I would not think that the shocks acting within
their normal range would have much effect on it. Either too soft or too
hard settings could affect the shock.
MG referred to them as 'dampers', which is a good description of what
they actually do. The springs absorb the shock of impact against a stone,
or hole in pavement, or bump. Once that impact is absorbed, though,
springs tend to continue to spring back and forth. The dampers damp that
motion, so that the initial impact is absorbed, then damped.
Back to the shakes---if the springs or the dampers are so hard that
bumps are transmitted right on into the chassis, that could cause real
shakes. If the springs and dampers were too soft, the bumps could get
the springs and dampers moving around so that shakes were not damped and
might even be set up by the suspension moving.
The T-series cars were separate body and chassis, with the largest
part of structural stiffness provided by the chassis. As the body was
framed in wood then covered with metal, and the doors were cut away to
the top of a wood frame, it's almost a two-piece body structure that can
wiggle at the doors. And it does---jack up the car at one corner and see
how the doors fit. That construction can permit a shaking that would
not exist on a unit-bodied vehicle.
The MkII TDs had adjustable Andrex friction dampers in addition to
the hydraulic Armstrongs or Girlings. Perhaps someone who has
experimented with the adjustments of the Andrex could answer your
question from experience. I keep the Andrex backed off to minimum
resistance, because I think they make the ride too stiff and it's my
opinion that they can slow the return of the tire to the pavement after a
bump. I don't know that to be true--it's just opinion. I haven't noticed
any particular speed at which a shake resonance occurs in the TD.
Bob
On Fri, 2 Aug 2002 18:56:42 -0500 "Bob D." <bobmgtd@insightbb.com>
writes:
> My B has always been pretty well shake-free. Maybe when everything is
> "right" on the B, and the road is smooth, there is nothing to excite
> the
> resonant vibration. But get on a bumpy road, and there you go.
>
> I wonder what effect the stiffness of the shocks has on shake? Does
> anyone
> have some experience here? I recently increased the stiffness of the
> front
> shocks on my TD in a vane attempt to fix a bad shake at 55 mph. (The
> resonant frequency speed of a TD?) I just tried new U-joints and the
> shake
> has gone away (at least the violent self excited shake). Now, on a
> bumpy
> road will stiff shocks cause more or less shaking?
>
> BTW: I never would have suspected my U-joints if it weren't for Bob
> Howard's
> advice about zero play. I'm amazed that a barely detectable amount
> of play
> can cause so much shaking.
>
> Bob Donahue (Still stuck in the '50s)
> Email - bobmgtd@insightbb.com
> 52 MGTD - NEMGTR #11470
> 71 MGB - NAMGBR #7-3336
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