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).
Comparing the riding quality and dynamics of a Silver Ghost Cabriolet and a Phantom Sedan.
| Identifier | ExFiles\Box 43\2\ Scan176 | |
| Date | 11th October 1926 | |
| E DA{Bernard Day - Chassis Design} COPY: X3900 OY13-E-111026. X8410 X5410 To R.{Sir Henry Royce} from OY. c. to Hs.{Lord Ernest Hives - Chair} RE. RIDING QUALITY. We have recently done some interesting work in comparing two cars at the Works with regard to their natural frequency of oscillation on the road springs. We think it is generally agreed that complaints of discomfort refer to the pitching frequency of the car (approx. 120 oscillations per minute) rather than the bouncing frequency of about 70-80 oscillations per minute which is of a speed to give a sensation of comfort rather than otherwise. This is obviously concerned not only with the distribution of the weight of the car (position of the centre of gravity) but also with the distribution of the mass of the car, that is its radius of gyration about the centre of gravity. To find the radius of gyration of the two cars, one a right-hand drive Silver Ghost with Cabriolet body and rear brakes, the other a left-hand drive Phantom with F.W.B. and large Sedan body, we swung each complete car as a pendulum about a transverse axis. Both cars were 143-1/2" wheelbase. The results we think would have been far more useful if we could have done the same for a 20 HP. (but we had no car available). However our conclusions are summarized below :- (1) The C.G. of the sprung weight was further back on the Phantom Sedan than on the Silver Ghost Cabriolet. Phantom 75.875" from front axle. Silver Ghost 73.500" from front axle. (2) The C.G. (without passengers or spare wheels) was 5" above the frame on the Phantom and 4" above frame on Silver Ghost. (3) The radius of gyration squared of the sprung weight was almost the same for both cars, 16.6 ft.² for Phantom 16.7 ft.² for Silver Ghost. Since the sprung weight of the Phantom was 4550 lbs. contd :- | ||