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 engine crankshaft stiffness, inertia, 'master period' vibration, and a summary of damper types.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 42 | |
| Date | 22th April 1927 guessed | |
| contd :- -9- Therefore the higher 'master period' on this engine is considered to be due to the following factors :- The crankshaft is considerably stiffer than that of the Goshawk and although this results in more than a proportional increase in inertia relative to the Goshawk the inertia is discounted to a certain extent by that of the big ends and pistons. This results in the stiffness factor being more important than the increase in inertia. The inertia at the front end of the shaft is a minimum, the crank pinion being transferred to the flywheel end. There is no evidence to shew that the fact of using a four bearing crankshaft in this case appreciably assists in placing the 'master period' vibration at a high speed. On an appended print we have shewn an approximate method of estimating the free period of vibration of the crank- shaft assembly. As stated before it is not perhaps a very accurate method due to the assumptions necessary for simplicity but it serves to shew the influence of various factors on the periodicity and has given fairly good results in cases where we have applied it. GENERAL SUMMARY. We know that even if the 'master period' is at a high speed it is very necessary to employ some form of damper to deal with harmonics of the gas pressure torque. There are two types - apart from others - that could be used :- (1) The RR. friction type. (2) The Harmonic Balancer type. contd :- | ||