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 performance report detailing chassis modifications, silence, vibration, and acceleration.
| Identifier | ExFiles\Box 182\M19\ img261 | |
| Date | 26th October 1931 | |
| Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/AM26.10.31 contd. -4- No form of centralized lubrication is fitted. The chassis is a foot longer than the well known Boulogne and 37 HP. and also increased in track. The brake drums have been increased slightly in diameter and pushed into the wheel. The radiator has been increased in size considerably and a larger fan with double belt drive fitted. A fabric coupling is used in the transmission. Silence. The valve gear is considerably more silent than that of the 6 cyl. models and in fact compares favourably with the average push rod engine. We had no opportunity of observing how much the noise increased during the "warming up" period. The silent second was very good though the change remained as previously, it being necessary to double de-clutch to obtain silent engagement. There was a slight carburetter roar at full throttle about 40 M.P.H. but not very noticeable, there was also a slight exhaust period between 30 - 40 M.P.H. but otherwise the exhaust was not obtrusive. The crankshaft period was clearly audible throughout the car at about 2500 R.P.M. as also was the valve bounce at 3000 R.P.M. Vibration. This car had little or no torque reaction and was very free from pick up vibrations of any sort. It was also quite free from over-run vibrations. The only noticeable period was at 2500 R.P.M. when a very definite crankshaft torsional period occurred. This was typical of its kind and appeared to be the crank vibrating about a central node at 4 times the normal master frequency and was about the amplitude of our half speed period with the damper removed. It existed over 3 - 4 M.P.H. on top gear. The valves left their seats at about 3000 R.P.M. Apart from the crankshaft period which could presumably have been dealt with by means of a damper correctly set, we consider that this engine was commendably smooth and free from "fuss". Performance. With a smooth unit having no torque reaction, the performance is always difficult to estimate, but the acceleration of the Hispano appeared to be exceedingly good above 15 M.P.H. This is to be expected on a 9 1/2 litre engine with a car weighing about 5000 lbs. at very low speeds on top gear the carburetter was at fault. | ||