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).
Gear design for the Goshawk 11 gearbox, discussing tooth obliquity, interference, and noise.
| Identifier | ExFiles\Box 75\1\ scan0230 | |
| Date | 7th September 1921 | |
| R.{Sir Henry Royce} from BY.{R.W. Bailey - Chief Engineer} c.c. GD. c.c. Ger. L.B. X4247 X4247 GOSHAWK 11. GEARBOX. With reference to the use of 20° obliquity on Goshawk 11 gears, I instructed these, as there is considerable interference between the gears with the small numbers of teeth used in the Pinion. In the case of the reverse pinion, only one half of the depth of the tooth is in use, the other half being cut away. The gears are not stub, but are a full height. We are instructing a complete set of 14½° obliquity, but one does not anticipate that this will materially affect the noise, as the arc of contact is the same on larger gears with a 20° obliquity and is considerably improved on pinions with a small number of teeth, owing to there being no interference down to a pinion of 12 teeth mating with the gear wheel in question. The gears, in any case, had to be cut in the experimental box on a Fellows machine, as it was not possible to obtain the necessary cutters to produce them Brown & Sharp. I quite agree that 20° stub teeth are noisy, but I have no information which would lead me to believe that gears of full depth made 20° obliquity on small pinions, are noisier than 14½° obliquity. As a matter of fact, recent information rather goes to show that as the number of teeth in the pinion decreases the obliquity of the gear should be varied since it reduces the amount of slip between the teeth. BY.{R.W. Bailey - Chief Engineer} | ||