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 design and performance of rear road springs, noting issues with plate thickness and stress distribution.
| Identifier | ExFiles\Box 80\2\ scan0174 | |
| Date | 30th June 1920 | |
| To R from DA.{Bernard Day - Chassis Design} Copy to BN.{W.O. Bentley / Mr Barrington} Copy to EFC. X.2628 X.4056 EFC RE REAR ROAD SPRINGS. ----------------- We have not completed our investigations of springs. Apart from the job being a lengthy one we have been somewhat delayed by the preparation of the bodywork etc., on 6EX. We have, however, discovered several interesting things. (1). The present springs, though so instructed, are actually not made with plates of constant thickness. They may vary in any one spring by as much as .100, and the graduation of thickness if not regular from plate to plate. Further, the thickness varies along any one plate. (2). The place where the point of maximum stress occurs may be at the point of support of any leaf by the tip of the leaf above, or it may be immediately under the central clip. Where it occurs depends on the shape and length of the overhang-ing tip, and very especially on the thickness of the plate underneath. It depends in fact, in the ratio between the tip load on any leaf and the reaction support offered by the leaf above. (3). Generally speaking, the effect of reducing the thickness of a leaf in springs such as our present ones, is to cause excessive stresses in the leaf immediately below. This accounts for the leaves frequently going in the centre on the bumping rig. The particular leaf which breaks depends principally on the way in which the spring is built up. It appears to us that the spring maker may be blindly putting up the stress in one leaf by substituting thinner leaves in order to get the required weight. Contd. Handwritten/Stamped text: Top left distribution list: To R from DA.{Bernard Day - Chassis Design} Copy to BN.{W.O. Bentley / Mr Barrington} Copy to EFC. Handwritten reference numbers: X.2628 (crossed out), X.2628, X.4056 Top right: JUL 27 (handwritten), RECEIVED (stamped), DA{Bernard Day - Chassis Design}23/CB30-6-20. (stamped) | ||