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).
Vehicle riding characteristics, shock absorbers, and the stiffness testing of road springs.
| Identifier | ExFiles\Box 55\3\ Scan293 | |
| Date | 12th November 1926 | |
| Oy3-E-111226 -2- November 12th, 1926 Riding. Our trouble is to combine smooth riding at speeds below 25 m.p.h with reasonable freedom from pitching at speeds from 35 to 65 m.p.h. If the front shock absorbers are easy enough to meet the first condition, they are too easy for the second, and vice versa. The comparative roughness of the low speed ride may be indicated accurately by water-spilling, but we should think high-speed pitching was best indicated by the actual effect on the rear passengers. Everything seems to show that the R.R. hydraulics will be the best yet for combining the two conditions, as well as dominating the front axle. All Phantoms we have tried we should characterize as extremely harsh at low speeds. Springs. We are making our own road springs, and are paying particular attention to the spring stiffness rather than free camber. The stiffness is measured as the average increase of load per inch, through a range of two inches, this range being for front springs 1" either side of flat, and for rear springs, flat to 2" neg. If the free camber is the standard with a tolerance of say ±1/8" it is quite possible to pass as 1100 lb. springs which are actually 1050 lb. or 1150 lb. We have recently measured some springs off English cars, with the following results: Spring Stamped | Actual Load 1/2" neg. | Nominal Stiffness | Actual Stiffness | Stiffness of spring indicated it should be stamped ---|---|---|---|--- 1100 | 977 | 355 (3.1 deflection) | 335 | 1040 1200 | 1052 | 387 (3.1 deflection) | 367 | 1135 2500 | 2516 | 833 | 770 | 2310 2350 | 2190 | 783 | 644 | 1932 2400 | 2405 | 800 | 771 | 2313 2600 | 2533 | 867 | 780 | 2540 | ||