I had the same problems on prewar cars (Bentley Tourer, Aston Martin).
The phenomena described in some british literature as "wobble" is
a movement in the front axle that rapidly increases and builds up
so much that you can't continue driving and have to stop the car
fast in order to stay on the road. Happens from time to time when
the car hits bad pavement (like typically cobble stones, or series of
pot holes). Don't know if the problem is what Dr. Owen describes,
but here is what my mechanic and I found out after much experimenting:
If a wooden or metal wedge is installed between the axle and the
chassis, everything is fine. The wedge gives a forward angle to the
axle (so the fat end of the wedge points toward the rear of the car).
We found that a thickness of the wedge of 5 millimeters is sufficient.
Cheap and simple, but solved my problem.
(excuse the clumsy wording - english is not my mother tongue).
At 09:29 28.08.96 +0100, Dr G W Owen wrote:
>
>Dear all (twice or some of you subscribed to both lists)
>
>Im after some advice following the first serious circuit outing of my new
>car (1928 Riley with 6.1 deHaviland Gypsy Moth engine). The track
>conditions were very wet (this may not be relevant)
>
>I am suffering from axle tramp under braking (medium to heavy). Also it
>seems as if there is ligght axle tramp at high speed. The car is
>semi-eliptic leafs at the front and 1/4s at the rear.
>
>What is tramp caused by? What is the motion of the wheel (up and down that
>should be stopped by the dampers or fore and aft which should be stopped
>by the stays from the chassis to the king pins)? How do I prevent it? What
>factors affect it?
> Spring stifness
> Damper settings
> Pre tension of stays
> Castor
> Wheel run out (currently over 1/8")
>
>Any advice appreciated
>
>Geraint Owen
>
>
>
Glue Man
glueman@collano.ch
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