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).
Technical discussion on the Salerni Coupling, its disadvantages, and proposed improvements.
| Identifier | ExFiles\Box 6\4\ 04-page221 | |
| Date | 3rd June 1929 guessed | |
| -2- contd. Salerni Coupling. This is one of the cleverest attempts at making an easy change. Personally I like the coupling in its simplest form, but I do not like the various devices to overcome its disadvantages. I will not attempt to describe it. Its chief feature is what I have called the baulk ring, which prevents the coupling jaws from getting into contact until the speed is synchronised, when the engagement becomes automatic, and practically instantaneous and silent. Mr. Hardy has suggested that to overcome the difficulty in connection with the reverse, which will not engage without some special devices and further manoeuvres, that the coupling may be placed in advance of the 1st. gear so as to cancel its action when used on the 1st. gear and the reverse. Its engagement will not be necessary for these two gears. At the same time should it become engaged it will have no ill effect. The other serious trouble is that one is very apt to stop the engine when the coupling becomes disengaged, which happens every time the clutch pedal is pushed down, and then it cannot be re-engaged without further devices and manoeuvres. To overcome this difficulty I have proposed that the disengagement is not made by the clutch pedal, but by the change speed lever, (either directly or by relay - preferably vacuum relay from engine suction) so that the coupling does not become disengaged unless it is desired to change gear, under which conditions the stopping of the engine would not be any more frequent than at present. As far as I can see these two ideas overcome the difficulties, and avoid the necessity for the complicated and unsatisfactory devices which require knowledge and care in manipulating. In the scheme of detaching the clutch by means of the movement of the change speed lever it is preferably arranged that the engagement will be made by the first part of the motion of the clutch pedal, so that the idea is that the main clutch pedal does not put the Salerni coupling out of engagement, but puts it in engagement if it is out, and the movement of the change speed lever puts it out if it is in, but has no power to put it in. The sketches herewith will enable these two ideas to be covered by preliminary patents (Sketches to Mr. Claremont). | ||