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).
Testing a 12-cylinder Kestrel Aero engine running on only 6 cylinders, with and without a flywheel.
| Identifier | ExFiles\Box 4\1\ 01-page017 | |
| Date | 21th November 1933 | |
| XFDD 4 To- Mr. ... From Mr/Mr. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} S/XT. 21.11.33. RUNNING 12 CYLINDER ENGINE ON 6 CYLINDERS. We have run a 12 cyl. Kestrel Aero engine on the test bed on six cylinders with and without a flywheel. There were various periods, the worst being at about 1700 r.p.m. We cannot believe that any of the periods would have broken the crankshaft unless the engine had been continually run at the speed in question for a very long time. None of the periods had the least resemblance to the master period which we get on our six cylinder car engines. The main reasons for this we think are as follows :- (1) We have nothing but geared aero engines, even though we fit a flywheel, therefore we always have slack between the inertia and the crankshaft. (2) The supercharger seems to have a definite effect on the periods. The six cylinder engine, which is doing various tests, gave continuous trouble with the magneto drives until the supercharger was fitted. This eliminated the trouble. (3) The dynamometer inertia is coupled to the crankshaft by a fabric coupling and this helps to complicate matters. The worst period seemed about as bad as the half speed period we get on the six cylinder car engines. We did the tests full throttle and light throttle and ran some little time on the worst period to see if we could damage anything. Nothing appeared to suffer. The frequency at which the periods occurred, given below, indicate that the 12 cyl. engine did not behave on 6 cyls. like an engine in a car. No Flywheel. Periods:- 750 Marked. 1450 Marked. 1850 Slight. 2375 Worst. | ||