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).
Issues and potential experimental use of the Salerni coupling on a 40/50 model.
| Identifier | ExFiles\Box 52\4\ Scan094 | |
| Date | 15th November 1930 | |
| HS. {Lord Ernest Hives - Chair} FROM DA. {Bernard Day - Chassis Design} X/F510 DA {Bernard Day - Chassis Design} 3/M15.11.30. SALERNI COUPLING ON 40/50. Though we have abandoned the Salerni coupling we think it will be possible to make use of it to confirm one or two points on our epicyclic gearbox experiments. We should like to demonstrate that the jaw clutches of the Maybach type, which are really practically the same as those on the Salerni coupling, will engage without shock. If you disconnect that part of the gear which prevents the clutch from going home until the Salerni coupling has gone home, and then let the clutch in fully and speed up the engine to the synchronous speed, it could be determined whether engagement was without shock or not. It would be necessary to be sure that the Salerni baulk ring was working correctly, that is, that there was sufficient friction to enable the engine to carry it round at the synchronous point. We may say that some of the defects you have mentioned in HS {Lord Ernest Hives - Chair} /RM {William Robotham - Chief Engineer} 1/M J11130., were not present on the car fitted up by Mr.Salerni which we tried, and should we think be easy of correction. Some of these are: (1) Difficulty in engagement of the coupling or of a gear in any forward speed from rest or when moving, and the possibility of the synchronous speed being overshot. No movement of the car should be needed for engagement or re-engagement. It is possible that there is insufficient friction between the engine and the Salerni baulk ring, so that the latter is not carried round, but lags behind. (2) The re-engagement device should always permit of engagement of the reverse without movement of the car. Another method of engaging the reverse is possible when there is 2" of free movement of the pedal before the coupling is disengaged, as is the intention of Mr. Salerni. On coming to rest the Salerni baulk ring is not disengaged, and you may go straight into reverse. Another way is to engage 1st. gear and load it up, but without movement of the car, and then withdraw it without withdrawing the Salerni coupling. We may say that the re-engagement device is never intended to be used except when the engine has been accidentally stopped during coasting, or for getting into reverse. This would eliminate the possibility of shock in engaging a forward speed in the way we think you describe. | ||