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 suspension dynamics, including deflection, rebound leaves, and air springs.
| Identifier | ExFiles\Box 43\2\ Scan193 | |
| Date | 26th January 1927 | |
| Oy1-E-12627 -2- January 26th, 1927 (1) p.25. We explain the observed fact that the frequencies are always higher than those given by considering the deflection only, by the effect illustrated in the attached sketch. It is usual, we find, for all experimenters to make a rough approximation to the actual elastic deflection, by adding the tire deflection to the spring deflection (5/8" for 5" tire, 1" for 6-3/4" tire). Thus on the 20 hp. we would call the total deflection in front 2-5/8" (theoretical frequency 116), and at rear 5-3/4" (frequency 78). We believe the actual pitching and bouncing frequencies will be rather quicker than these because of the fact that k²/ab is less than 1. But we should expect k²/ab for a typical 20 hp. to be always larger than the ratio .455 to .53 which we find for the 40/50. (max. value found on 40/50) With 500lb load at rear + 4 passengers. k²/ab = .665 For the latter, with 6-3/4" tires we should call the front deflection 4.1" (theoretical frequency 92.5), and the rear 9" (frequency 62.5). Actually the pitching speed (obtained by bouncing the front end) is about 120, and the bouncing speed (obtained by bouncing the rear end) about 75-85. By July 4/17 (2) Rebound leaves. (p.18). I can understand that rebound leaves will reduce the flat load, but cannot see how they reduce the rating. The case is similar to two opposed helical springs, as in the side steering tube, where the rating is equal to the sum of the ratings of the two springs. In other words, adding leaves will increase the stiffness of a spring whether the leaves are bent upwards or downwards, but in the first case the flat load will be increased and in the second, decreased. (3) Air Springs. (p.23). Have been greatly interested by this section because of the Hofmann air spring, introduced by Joseph Hofmann (the pianist) which consists merely of an inflated rubber ball. I enclose blueprint of a proposed installation and letter of May 29th showing a picture of the device. We can have a set of these any time by asking for them. My objection to them has always been that I could not see where any damping friction was introduced (except the slight heat loss in the compressed air) and I have always considered that mere | ||