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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of chassis frame twisting, radiator movement during 'jellying', and the effect of the frame on wobbles.

Identifier  ExFiles\Box 15\1\  Scan228
Date  19th February 1930 guessed
  
-3-

from side to side, or .187" in either direction from the central
position. The greatest amplitude of movement that we have
produced by our artificially excited test is .650". Therefore
the angle through which the frame is twisting on the road in
the case of the worst S.S. car that has come to our notice
is rather less than 1°. This indicates some of the difficulty
we have experienced in reducing the small movement on such
an awkward structure as a frame.

(5) The engine does not move as much as the radiator when "jellying" occurs.

We have measured the engine movement at the same
height as the radiator cap. It is only 2/3rds. as much as
the radiator. This is because the rubber engine mounting is
sufficiently flexible to allow the frame to twist a little
without moving the engine. This is quite clearly discernible
on our test by the contortions of the hose pipe which connects
the radiator to the engine. We also know that four solid
engine feet are the easiest way to cure radiator movement.
However, we cannot depart from our present flexibility or we
should run into engine roughness.

(6) Effect of Frame on Wobbles.

Since the axle is the motive power that initiates
and sustains "jellying" it might be thought that this should
be altered rather than the chassis to overcome the trouble.
However, the two are not independent at all and we actually
find that practically, it is easier to alter the amplitude
and frequency of the oscillation by attacking the torsional
stiffness and moment of inertia of the chassis and body than by
anything we can do within the scope of practical application
  
  


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