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).
The cause of a musical note in gearboxes and proposals for testing.
| Identifier | ExFiles\Box 75\1\ scan0008 | |
| Date | 22th December 1911 guessed | |
| GEAR BOXES (Contd.) (9) "The diaphragm which isolates the intermediates has a musical note, but it is too high - it may be an accessory but not the prime cause. The column of air crossways in the box at this period would yield the right note if it acted as a tube open to one end. There are openings at each end, however - one for the shaft to pass through, the other for the change speed mechanism; but on running a box on the gear box rig I found that the latter aperture was completely blocked up by the oil thrown up so that actually there is a tube (irregular in shape it is true) under the proper conditions to accentuate the note mentioned. If true the cure is a hole or two in the diaphragm. The easiest way to test is to empty the oil from a box. I should expect then to get the loudest sound an octave higher than before, i.e. at twice the speed, but by that time other noises would mask it probably. The theory simple explains why when the oil is less viscous the noise sometimes disappears; and why good gears in a box with noisy intermediates are cured (two series of harmonic vibrations superimposed.) To pass I think our intermediates have not merely to be good gears, but well nigh perfect gears. It is clear we could not detect a howling side shaft on any rig that we have at present, neither can we until we have an engine entirely for such tests and experiments." The Committee discussed Mr. Whitehead's note and agreed that the theory put forward was worth the test. Mr. Whitehead should go further into the matter and make what tests in this direction he thinks are necessary on a gear box which Mr. Wormald will prepare. Mr. Platford informed the Committee that he had roughly tested this idea by removing the oil filling plug, but without success. He | ||