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 providing a critique of shock absorber literature, discussing damping frequencies and roll.
| Identifier | ExFiles\Box 152\2\ scan0188 | |
| Date | 9th April 1940 | |
| 1293 Rm{William Robotham - Chief Engineer}/C1m.1/JH. 9th. April, 1940. C. Piazzolla Esq., Dear Sir, We have examined the shock absorber literature you left with us, and we return it herewith. We trust you will take our criticisms in the spirit of helpfulness in which they are offered. In the first place may we point out that a shock absorber has to deal with two specific frequencies. One concerns the motion of the car about the axles, the other of the axles about the car. These two motions have widely differing frequencies about 80 - 100 and 500 - 600 cycles per min. respectively and the amplitude may be just as large in the high frequency motion as in the low frequency one. Therefore it will be clear that a damper which gives sufficient damping for the low frequency large amplitude motion will give far too much damping for the high frequency large amplitude motion. In this latter case only a very little damping is really required. We therefore consider that any satisfactory damper must have a blow off valve of some sort to deal with the high frequency motions. We note that you claim that the damper opposes roll on corners. Our experience shows that no hydraulic damper having an open orifice between the two working cylinders can affect the angle of roll to any measurable extent. Cont'd.{John DeLooze - Company Secretary} | ||