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 the causes and proposed solutions for erratic synchromesh working in the Phantom III Gearbox.
| Identifier | ExFiles\Box 94\1\ scan0293 | |
| Date | 8th January 1936 | |
| To E.{Mr Elliott - Chief Engineer} C. to By.{R.W. Bailey - Chief Engineer} C. to Md. X328 Rm{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux}15/KW.8.1.36. Phantom III Gearbox. The result of our investigation of the erratic working of the synchromesh has proved that the premier cause is the distortion of the bronze cones with resultant loss of the necessary friction to synchronise the gears, causing faulty engagement. We have by careful grinding in of the cones in their assembled position in the box made two imperfect boxes into good ones. We got them to the state that it was impossible to crash the gears, although there was a certain amount of delay of time for the synchromesh to take place. This is felt by a slight lumpiness before the change speed lever is in its correct position with the gear engaged. This lumpiness and time factor we have improved by fitting only two plungers in the sliding sleeve in place of the standard six. This decreases the static load to move the sleeve (i.e. compressing the plunger) from 30 lbs. to 12 lbs. It allows the freer working of the loading sleeve which in turn ensures the correct working of the synchromesh unit. We have also made an improvement for the more positive location of the plungers during the change from 3rd to top and vice-versa, by having the location surface of the plungers made a true spherical in place of the angle and partial spherical. There is less tendency for the plunger to be flipped up when striking the groove. With the careful grinding in of the cones assembled in the box with a small amount of paste, then washed thoroughly out, there is no reason why passeble boxes should not be obtained. We are meanwhile investigating further to delete the time factor for the synchronising and over-coming the distortion of the bronze cones. We have, as an example of a good synchromesh the Vulture gearbox. This has run a considerable mileage and has given no trouble. We dismantled the box to ascertain the reason for its good qualities. The first and foremost thing noticeable was the good condition of the bronze cones. The bedding checked was found to be 100%. There was no sign of distortion of the bronze cones. The location of the plungers of the sliding sleeve was positive. This was due to the groove in the sleeve being machined to a truer sphere. [Handwritten in left margin]: G.W.H. of a good box on SpectreCodename for Phantom III I should like a demonstration (I'm) | ||