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).
Summary of crankshaft vibration tests analysing resonance and the effects of running the engine with and without a propeller.
| Identifier | ExFiles\Box 43\3\ Scan141 | |
| Date | 10th March 1927 guessed | |
| contd :- -3- Repeating these experiments on the test bed con- siderable trouble was experienced with the apparatus at the lower speeds due to the unsteadiness of the engine speed made manifest by the absence of a flywheel or prop: Naturally variation in motion during rotation affects the instrument because the flywheel part of it tends to maintain a constant angular velocity. However there was no evidence of a state of reson- ance at 1470 r.p.m. - the previous synchronous speed when driving a prop: At 2000 r.p.m. and it is at this speed that we are more interested, it was found that the diagrams obtained were 'smoother' than when driving a propeller. In all these tests we have been unable to make more than a general analysis of the vibration diagrams as we are not satisfied that they are accurate enough to yield more than com- parative results. As a general summary of the crankshaft tests, we should say :- (1) A resonant period appears to exist at 1470 r.p.m. when driving the airscrew. This we conclude is the master period and has six cycles per rev. (2) No indication is given from the diagrams of reson- ance over the speed range when on the test bench. This would be due to the absence of the propeller inertia. (3) At the normal running speed - 2000/2100 r.p.m. - the crankshaft motion appeared 'smoother' when on the test bed than when driving a propeller. Having established that a vibration existed at contd :- | ||