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).
Analysis of crankshaft inertia, synchronous speed, and the effects of spring drives, with reference to Goshawk and 20 HP engines.
| Identifier | WestWitteringFiles\Q\February1927-March1927\ 70 | |
| Date | 1st March 1927 guessed | |
| contd :- -2- CERTIFICATE OF INSPECTION BY A.I.D. No form of damper or balancer is fitted to this shaft and the camshaft and accessory drive is taken from the flywheel end, probably for that reason, although apart from the extra stiffness, removing inertia from the front end of the shaft we have proved to be an important factor in raising the speed of the 'master' period. Some recent experiments on the Goshawk show that if we remove the complete spring drive unit from the front end of the crankshaft, leaving the front end of the shaft bare, by motoring over by means of a belt drive we raise the synchronous speed to 3750 r.p.m. from 3300 r.p.m. The raising of the synchronous speed we consider to be due entirely to the removal of the inertia due to the hub of the spring drive as the crank pinion - i.e. the spring parts - would have little or no effect. On 1-G-1 the synchronous speed occurs at approx. 3850 r.p.m. and this relatively high speed compared with the standard 20 HP. we attribute to the forward mass being, so to speak, 'sprung'. Only half of the friction plates and the carrier contribute to the polar inertia of the front end of the crankshaft in this design. Inertia concentrated at the front end of the crankshaft is a greater factor in lowering the resonant speed than the inertia of the crankshaft itself for the reason that the equivalent inertia of the crankshaft, assumed concentrated at the front end, is only one-third of the total inertia of the shaft itself. contd :- | ||