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).
Nature, cause, and testing methods for a vibration issue in a Phantom car engine.
| Identifier | ExFiles\Box 13\7\ 07-page088 | |
| Date | 20th February 1931 | |
| E.{Mr Elliott - Chief Engineer} HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} (At Le CanadelHenry Royce's French residence.) R1/M20.2.31. X.634. X.7300 X.5300 C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to PN.{Mr Northey} RHC.{R. H. Coverley - Production Engineer} VIBRATIONS - CAR ENGINE BALANCE WEIGHTS, ETC. So far we cannot come to any satisfactory conclusion of the real nature of the vibration which is troubling the Phantom cars. HS.{Lord Ernest Hives - Chair} says it is worse at 65 MPH., then gets better. This is 2500 revs., and strange to say is the same revs. as the periodicity of low speed torque reactions. The most promising way of finding the nature of its source is to test if it is 1 or 3 per rev. Mr Clarke could easily rig up an electro motor to run 2500 revs. shunt wound for 12 V.{VIENNA} - further suggestions later in memo. with some resistance in the shunt exiting circuit. Let it have a pulley slightly out of balance and be placed inside the body to see if produced the boom, and it would therefore shew if the periodicity was 1 or 3 per rev. various motors and voltages could produce periods up to say 8000 if it were found necessary. According to reports it must be a natural period - some engine part (or frame and engine combined) or the body - because it comes to a maximum at some speed and lies away at still higher speeds. If it is 1 per rev. it is not torsional because our torsional period is 3 per rev. or more. It would therefore be the crankchamber or flywheel. Assuming it was 1 per rev. how can we raise its period. Balance weights might lower it slightly (but definitely lessen its intensity) because we have added mass but not altered the rigidity of anything. If we lighten the flywheel or make it more rigid we put up the period of the flywheel but we do not alter the crankchamber periodicity. It would be useful to know if the body responded to vibrations other than at 2500 - i.e. if the body booms by the out of balance motor running 1500, 2000, and 2500; with 2 car batteries we could get different EMFs. - 12, 18, 24, by exiting the motor with one or both batteries and supplying the armature current from 6, 9, or 12 cells. If the body would only respond to one periodicity then one would say that the body was definitely at fault, because even a small out-of-balance would probably put it in a state of vibration if this was its period and it was a part that was not damped. I am so very disappointed that all our suggestions bring no very definite light on something which still seems a mystery. It will be noticed that Mr. Grylls test of stiffness of crankchamber seems to be without lower half or cyl. block, and therefore not much to go by, and may account for his large deflection which does not occur in a complete engine. (1) | ||