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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).
Technical analysis of diagonal or criss-cross oscillation caused by tyre errors and leaf spring systems.

Identifier  ExFiles\Box 29\1\  Scan274
Date  16th September 1925
  
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BY7/H.{Arthur M. Hanbury - Head Complaints} 16.9.25.
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data really contradicts this theory, if analytically considered, this seemed to me untenable.

If one starts with the fact which is well ascertained that the tyres are the initial causes due to dimensional errors or out of balance of mass and most probably both, it is plain that such errors will cause the axle carried as it is between leaf springs and air cushions, to oscillate vertically. This oscillation may be one in which axle remains parallel to the ground in the first instance, but since one wheel inevitably gets out of step with the other, it ultimately becomes a diagonal or criss-cross oscillation.

Once the "diagonal" oscillation is set up, it persists because the system is one which excites itself. There are two heavy masses supported on the ends of a long bar with two supporting leaf springs arranged between the mass. The diagonal oscillation of this system then is such that one mass reacts from its supporting intermediate spring on the other system in the same direction as the existing motion, and therefore adds to it, and with the irritation of the tyre error persistently pushing the system at each end, the oscillation rapidly grows in amplitude, and as one tyre is invariably greater in its error than the other, this forms the constant impulse which keeps the system swinging.

Contd.
  
  


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