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).
Notes on riding quality, focusing on the distribution of mass and oscillation frequencies.
| Identifier | ExFiles\Box 43\2\ Scan217 | |
| Date | 28th August 1927 | |
| Oy9-E-92327 V3900 August 28, 1927. NOTES ON RIDING QUALITY Distribution of Mass. The classical assumption that all bodies supported on springs having the same deflection, oscillate at equal frequencies, only applies to bodies supported on single springs underneath their centres of gravity. It does not generally apply to bodies like automobiles supported on springs at each end, the difference being that in the latter case the oscillation is more rapid than the theoretical oscillation of the first case. Simplest demonstration of this fact is shown in attached sketch where a mass M is supported in one case on a spring with deflection d, and in the other case double the mass (2M) is supported on a spring having the same stiffness and deflection d at one end and on a pivot (i.e. an infinitely stiff spring) at the other end. The times of the swing of the two cases are given. (First case, i.e. t = 2π√(M/S) is the same as saying that the frequency of oscillation of any body supported on a spring is equal to the frequency of swing of a pendulum having a length equal to the deflection of the spring.) The simple rule of the first case (t = 2π√(M/S)) does apply however in the particular case (see sketch III) where k² (radius of gyration squared) = a x b. This is equivalent to two masses concentrated over the springs. Such a system has the following desirable characteristics. (a) The lowest oscillation frequency, which is very likely to be obtained in a car, for springs of a given stiffness. (b) The oscillation at either end is not transferred to the other end i.e. front oscillations are not felt at the rear. As far as we know the condition III is never attained in automobiles, but we have the "hunch" that it is approached in smaller cars like the 20 hp. or in special jobs like the Lancia Lambda. Hs.{Lord Ernest Hives - Chair} has promised to make some tests on the 20 hp. to prove whether this is so. | ||