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).
Investigation and analysis of engine vibration at various speeds.
| Identifier | ExFiles\Box 25\3\ Scan366 | |
| Date | 13th November 1928 guessed | |
| contd :- -10- wheel case gears were left untouched. We noticed that the engine vibration from 30/40 m.p.h. in 3rd. gear was about 80% less than when pistons and rods were fitted. At 41 m.p.h. (2960 r.p.m.) a bad period appeared, but after this it was smooth up to 50 m.p.h. This period was similar to the main crankshaft period but about 1/4 as rough. Normally the main torsional period occurs at 47 m.p.h. in 3rd. on this car. It was possible to detect that the vibration was very great at the centre and front of the crankcase, zero at the flywheel and rear engine feet, and great at the rear of the gear box, and that the motion was principally in a vertical plane. We removed the cyl. block but this did not permit the vibration to become more serious. We also proved there was no torsional vibration of the crankshaft, since the slipper wheels did not reduce it; neither did removing the steel blocks alter the frequency, although it reduced the polar moment of inertia by over 50%. The severity of vibration was not reduced by any noticeable amount when the blocks were removed. We next removed the crankshaft and substituted a plain parallel shaft the same dia. as the journals, with the flywheel and wheelcase gears attached as before. The period disappeared then, and there was no trace of vibration at any speed up to 50 m.p.h! A possible explanation of the period is 'whirling' of the shaft in some way, but we think this is ruled out since its frequency should be dependent on the weight of contd:- | ||