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).
Investigation into noise and 'chunking' issues with the Spectre gearbox, detailing experiments and comparisons with other models.
| Identifier | ExFiles\Box 94\1\ scan0127 | |
| Date | 21th May 1935 | |
| To E.{Mr Elliott - Chief Engineer} From Ha/Gry.{Shadwell Grylls} c. to Wor.{Arthur Wormald - General Works Manager} c. to Hy.{Tom Haldenby - Plant Engineer} c. to RHO. 8328 Hs{Lord Ernest Hives - Chair}/Gry{Shadwell Grylls}1/MJ.21.5.35. SPECTRECodename for Phantom III GEARBOX. Since the dynamometer testing of this gearbox we have been experimenting to reduce the noise both idling and on the indirect gears, and secondly to eliminate 'chunking' particularly when changing from drive to overrun or vice versa. As regards noise we have found that a very considerable amplification of noise is caused by the change speed mechanism. When the whole bracket is removed, most of the hissing noise of idling vanishes and the indirect gear noise is greatly reduced, but never reaches the standard of the present Phantom. We are making a cast aluminium bracket instead of the steel construction to see if this is less resonant. Improvements in noise with the existing bracket were effected by ribbing the sheet aluminium gate and cover and felting the whole bracket. To prevent chunking (which on 3rd. gear especially is of an impossible amount on all three cars) we have on No.1 car taken all float out of all three shafts by HAF's end clamping scheme N. Sch.4448. This had no effect on chunking but did, we think, improve the gear silence. Provided we can show on a 10000 miles test that the end load does not vanish owing to wear of the washers we recommend this scheme for production as accurate clearances no longer are required. Having noticed excessive end movement of the 3rd. and 2nd. speed free pinions we had these fitted with pressed in bushes of .001 clearance on the diameter endendways. This again had no effect. At this time the J.3 gearbox was again fitted to the Vulture and proved to be free from chunking on all gears. Backlash tests of this box and all three SpectreCodename for Phantom IIIs and the Buick were therefore taken and can be compared from the attached table. These results show a large amount of slack on the particular gears of those cars bad for chunking. The Vulture and the Buick are free from the trouble but all the SpectreCodename for Phantom IIIs impossible on 3rd., SpectreCodename for Phantom III 1 on top gear, SpectreCodename for Phantom III 111 on 2nd. gear, and none of them nearly so bad on 1st. speed. We concluded that excessive backlash in the gear teeth is the cause of the noise, and would add that on both the Vulture and the Buick the end clearance of the shafts is considerable without affecting adversely this trouble. Slack in the clutch splines must also be the minimum possible. Ha/H.Grylls. | ||