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).
Error and subsequent modifications related to using 20% stiffer springs on the Phantom car.
| Identifier | ExFiles\Box 67\2\ scan0289 | |
| Date | 1st March 1927 | |
| X8420 Hs.{Lord Ernest Hives - Chair} Wor.{Arthur Wormald - General Works Manager} Hm.{Capt. W. Hallam - Head Repairs} MAR 1 1927 RECEIVED BY2/H.{Arthur M. Hanbury - Head Complaints} 1.3.27. 20% STIFFER SPRINGS. Referring to your memo on the above subject, and dealing particularly with the Phantom car, I find that we made an error in the Drawing Office in stipulating that the packing should go between the rubber buffer and the frame. The dimension we now specify, namely, 3.650", is correct, and is the one we should have specified in the first place. Originally I was responsible for the suggestion that for certain countries modified springs should be used, but my original suggestion was 25% stronger. R's criticism and counter-suggestion was that the stronger spring would put the car up on stilts, and it would be advantageous, therefore to use a 20% stiffer spring, that is, put up the rating of the spring, and to produce a new type of spring to incorporate this idea, which of course necessitated reduced free camber. In regard to the further point you raise, that you cannot see that there is any material difference so far as the spring breakages are concerned, between the 20% stiffer springs fitted and our ordinary standard type, under similar conditions, I think the point overlooked is, that whilst the direct stress is the same in both springs, the indirect stress, namely, that due to lateral bending of the springs as the result of an angular axle motion, is very distinctly reduced. At the time the proposal was made by myself, and agreed to, we had no special 20% stiffer springs available, and for a considerable period we fitted the stronger springs. The stronger springs, of course, reduced the deflection of the spring for any given bump. This reduced the lateral bending stress, and the effect was that we immediately cut out breakages of springs which were occurring. We are arranging for Hm.{Capt. W. Hallam - Head Repairs} to get out a sheet instructing our Depots in the Countries where special springs are fitted, to remove the packing and replace same with a reduced thickness to ensure the correct amount of clearance being available where stiffer springs are fitted. We raised the question recently with HS.{Lord Ernest Hives - Chair} as to whether we should be able to reduce the strength of the springs when hydraulic shock dampers were fitted. One is inclined to think that if we fitted 15% stronger springs with shock dampers, for Contd. | ||