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 characteristic car movements and vibrations related to shock absorbers.
| Identifier | ExFiles\Box 55\4\ Scan239 | |
| Date | 13th July 1928 | |
| ROLLS-ROYCE OF AMERICA, INC. SPRINGFIELD, MASS. 8235. OY3.R.7.13.28 July 13th, 1928. Mr. Robotham, Rolls Royce Ltd., West WitteringHenry Royce's home town, England. Dear Mr. Robotham: RE SHOCK ABSORBERS - SECTION 7150/60 Many thanks for your reports with indicator diagrams showing what happens inside the instruments, and for your promise to test the leaking valves. (1) Regarding characteristic car movements, we think (from earlier riding-quality trials) that they can be divided up roughly as follows:- (a) Criss-cross vibration of front axle .550-600 vibrations per minute. Approx. 1" maximum allowable stroke. (Frequency determined by marks on road during H.S. wobble. We have guessed at maximum allowable stroke based on what you showed me on the bump test and on the fact that the tires deflect about 1" under load.) (b) Chatter of rear axle on a "washboard" road. 450-500 cycles/min. Approx. 1" max. allowable stroke (because of tire deflection) Frequency observed by riding in car with rear seat boards open and timing with watch held to ear. (c) "Pitching" of car, i.e. criss-cross longitudinal motion, front and rear springs moving in opposition. 120 cycles/min. Approx. 2" maximum allowable stroke front and rear. The center of oscillation is a little to the rear of the center of the wheelbase but we have assumed 2" stroke front and rear. Frequency timed with a watch, approximately two cycles per second on all cars with 6-3/4 tires and springs properly lubricated. (d) Bouncing of car. (Commonly known as "rear spring action" and generally considered a desirable feature of the R.R. car.) (Continued) | ||