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).
Letter discussing the specifications and stress analysis of rear springs for a 20 HP model.
| Identifier | ExFiles\Box 52\2\ Scan252 | |
| Date | 15th October 1930 | |
| Mr. J. {Mr Johnson W.M.} Wortley Fawcett, Tinsley. 15th. October, 1930. be willing to adopt in springs of 66" span to their drawing No. 79439, i.e. the same drawing number as for item 1. Item 3. This calls for a pair of springs similar to the present 20 H.P. rear springs but loaded to 820 lbs., and to give a deflection under load, of 8" instead of 5 1/4" as at present. The same general remarks apply in this case. The ratio of increase of stress, assuming the same main plate thickness as at present, will be 52 1/2 per cent. We should, therefore, like a statement from Messrs. Rolls Royce, as to how much they would be willing to have the main plate thickness reduced from its present value of .281". The range of stress at present used in this design of spring from free to loaded position, is 24.4 tons/sq.in. I think it will be appreciated that the stresses employed in springs are very high in comparison with those employed in other motor-car parts. The stresses mentioned in the foregoing are those for dead load only. The usual static test applied in the shop carries the deflection to a position of maximum bump specified by Messrs. Rolls Royce, and this generally corresponds to an addition of about 60 to 70 per cent. on the above values. The stresses which the springs actually receive in service may be even higher than the above values. We shall be pleased to go into the matter further on receipt of Messrs. Rolls Royce's comments. C Stanfield | ||