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 from Cadillac Motor Car Company regarding testing and development of shock absorbers.
| Identifier | ExFiles\Box 4\6\ 06-page49 | |
| Date | 12th May 1931 | |
| COPY. CADILLAC MOTOR CAR COMPANY. DETROIT, MICHIGAN. Experimental Dept. Rolls-Royce Ltd. Derby, England. May 12th, 1931. Att. Messrs. Hives and Robotham. Dear Hives and Robotham, Thank you for your letter of March 20th on Delco shocks and April 22nd on miscellaneous details. Shock Absorbers. The report on shocks has spent some time at Dayton and has been most useful. They are greedy for more along the same lines particularly anything which would more fully describe the apparatus used and which would tend to show up any defects in action of the shocks which may exist at high frequencies. We are paying a lot of attention to frequency. A 3 foot bump at 100 ft/sec (68 m.p.h.) represents 2000 cycles a minute and we think that all such high frequency impulses must be absorbed by the tyres. We figure that the shocks begin to work at 670 a minute for the front axle and say 480 for the rear axle, and that from that frequency down to 100 in front and 80 at the rear they must give a full and smooth indicator diagram. The typical concrete road wave having a sine curve form of say 3" rise in 30 foot length introduces an entirely new problem in causing extremely high accelerations (principally downward) to the sprung mass while producing very small relative velocities of axle to frame. We feel that this condition calls for - (a) Supplementary dry friction. (b) "Preload" on the shock absorber valves before leakage starts. (c) Some means of making the shock absorbers sensitive to movement of the car itself. ("Inertia valves" etc.) | ||