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).
Investigation into the Phantom III front suspension's load deflection curves and a proposal for new springs to achieve constant periodicity.
| Identifier | ExFiles\Box 95\2\ scan0082 | |
| Date | 7th May 1936 | |
| To DY.{F R Danby} Copy to Dr. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Phantom III Front Suspension. For some while we have been making investigations into the load deflection curves for the Phantom III front wheel. Due to peculiarities of the overall leverage and of the tilting of the yoke piece the load deflection curve is not a straight line, but deviates from the theoretical straight line curve on both bump and rebound. For a straight line load-deflection curve the frequency-deflection curve is one following a harmonic law. That is to say, the periodicity is not constant. In the case of the present standard Phantom III front suspension the load-deflection curve is not straight, but shows a diminution in rating on bump and a tendency to an increase on rebound, due to the leverage variation and the angularity of the wheel to the vertical. It is believed that for a suspension with freedom of pitching requiring the minimum of damping, the periodicity of the front and rear suspensions should be constant for all deflections, and themselves equal to each other. At the same time, all other things being equal, one would like to use springs with 10" deflection both front and rear. We have found it possible to provide the present Phantom III front suspension mechanism with springs of both 7" and 10" static deflection, alternatively having a constant periodicity. On N.Sch.4807 herewith we show the design of these springs, and also graphs showing the 7" and 10" static deflection springs. We have shown both circular and square wire for the main spring which is in constant use but we suggest that for the first experiment the round wire be used. We are aware that the stresses in all of these springs are higher than we normally use, but as this is only in the nature of an experiment to demonstrate the desirability or not of constant periodicity, we do not think this should matter. In the case of the 7" static deflection the periodicity is 72 throughout, which is the same as the periodicity at normal load with the present standard springs. | ||