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).
Spring ratings, calculation methods, and a request for data suitable for Australia.
| Identifier | ExFiles\Box 67a\2\ scan0116 | |
| Date | 10th March 1928 | |
| To Pt. from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG10.3.28. Thank you for Pt10/FM31.12.28. We agree that 'initial' is confusing, perhaps 'free camber' is the best. You mention you don't understand the spring rating shewn in our "Car Performance" file. Its wrong. The rating of our 2000 lbs. cantilever spring by definition is a spring that when loaded at the centre with 2000 lbs. deflects 6" at the working end, or in other words, 2000/6 lbs/1" = 333 lbs/1". However that rating is only used for ordering the spring, because on the car we load it at the end, not the centre, and in consequence the rating is halved. . . . true rating (for direct comparison with 40/50 front or 20 HP. front and rear) is 333/2 or 166 lbs/1". True rating of 82-LC which you quote 480/2 = 240 lbs/1" i.e. rating for a very heavy car 25% stiffer springs. We thank you for your method of springing cars which we will investigate but really far the simplest and easiest thing to go on is the buffer clearance. It takes only a moment to measure and gives all we need this end. Could you give us an average that suits Australia. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||