Rolls-Royce Archives
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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).
Suspension damping, orifice effects, and the phenomenon of 'boulevard jerk'.

Identifier  ExFiles\Box 170\2\  img103
Date  18th October 1931 guessed
  
low "dry friction" in the suspension, the lack of damping at the inception of axle movements allows them to build up to greater amplitudes, & shake the car actually more with orifice than without.
We do not find that we can dispense with orifice entirely even when we have -
a) very light damper loads
b) Exceptional spring lubrication.
c) Low "build up" in the dampers.
- because, without some orifice effect we get "boulevard jerk", which we find to be nothing more than the natural bounce & pitch-frequency (principally pitch) of the car as a whole on its tyres, the tyres being springs of approx 2000 lbs/in & giving frequencies in the neighborhood of 250-300/min.
We do find however that orifices between .0005 & .0010 square inch such as we used on the Spfld Rolls, are adequate to get rid of boulevard jerk without detracting from stability. The effect is about like curve A above.
Having got so far, the next step is obviously to regulate shocks by varying the spring-load on the valves, which can be quite simply done.
  
  


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