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).
Visit to the company 'Numbers' to investigate the quietness and manufacturing process of their 'Phoenix' gearbox.
| Identifier | ExFiles\Box 112\2\ scan0035 | |
| Date | 15th September 1937 | |
| 1044 By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} 828. Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}/R.15.9.37. PHOENIX GEARBOX. Hdy.{William Hardy} and I visited Numbers to-day in order to see what standard of quietness could be achieved in gear-boxes with cyanide hardened unground gears. Numbers put themselves to considerable trouble to give us all the information we wanted. We were taken out on three demonstration cars, all having the same type of gearbox, viz., the largest they make. On none of the cars was the standard of silence as good as that on any Rolls-Royce chassis. The first of the three was noticeably the best, and would probably be quiet enough for Phoenix if we are going to accept a standard inferior to what we have accepted before. The next two cars were unquestionably too noisy. The steel used in this gearbox is known as Clyde Alloy NRM3, and has a much better impact value than the Ford material. Some of their gears are said to run at a Lewis stress of 140,000 per square inch, which is higher than we have contemplated. The gears are hobbed, then shaved in a Michigan shaver, cyanide hardened, water quenched from a temperature of 230, and after these operations the bore is ground from the pitch line, and the gears then lapped on an arbor fitting this ground bore. Some of their output is lapped in an american machine in which individual gears are lapped between three large cast iron wheels. They say they get much better results by mounting all the gears on their shafts in a rig exactly representing their positions in the final gearbox, and then running them with a slight oscillation of the layshaft, using a lapping compound. We also examined the fit of the sliding 1st speed wheel on the 3rd motion shaft. The shaft itself has ground splines and the bore of the gear is ground after heat treatment. They have to use selective assembly to get a good fit, saying that they suffer from transmission rattles if this particular gear is loose. We tried several gears on a shaft; one would not go on, but all the others were an exceedingly good fit showing that there had not been much distortion during the cyanide treatment. | ||