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).
Engine smoothness and power characteristics, detailing vibration periods and torque.
| Identifier | WestWitteringFiles\T\November1928\ Scan023 | |
| Date | 3rd November 1928 guessed | |
| contd :- -2- fact that the tyres were dead smooth (the car has done 8000 miles) one could drive it really fast on wet roads with no apprehension. ( 2) Smoothness of the engine. The engine was remarkably smooth up to 5,500 r.p.m. There being no crankshaft damper, all the periods of the 6 cyl. engine could be heard (but not felt) by judicious driving under full torque. They occurred at 5000 (master) 3280 (2/3) 2500 (1/2) 1650 (1/3) 1250 (1/4). The worst period by far was the half speed, next in intensity the one at 3280. The most surprising feature was the feebleness of the main period, we do not know how to explain this except by the fact that the gas torque was falling and so there was not a high M.E.P. to produce it when pulling, and the reciprocating parts were so light in relation to the shaft size that the inertia torque did not bring it up violent-ly on the overrun. Incidentally we understand that this shaft is fitted with counter weights. Actually one could only detect the main period by a broad band of roughness over 300 r.p.m. or so worst on the overrun. We feel almost certain that all these periods would be dealt with with the normal crankshaft damper, when the engine would become unique for absence of vibration. (3) Engine power. The M.E.P. does not fall appreciably until just before 5000 r.p.m. There are no flat spots. Starting up is easy. There was nothing to indicate that one was driving a vehicle with a super efficient power unit, except the surprising acceleration and liveliness. Low speed torque was naturally not very good but the car could be driven in traffic at 6/7 m.p.h. on top gear. contd :- | ||