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).
Comparison and critique of various gearbox designs, including epicyclic, Wilson, Salerni, and spool gears.
| Identifier | WestWitteringFiles\V\October1930-February1931\ Scan003 | |
| Date | 1st October 1930 guessed | |
| (2) little too elaborate and complicated for profitable production- (some of No. 3. has gone to Derby.) This 4th. scheme consists of the same epicyclic accelerated train and reverse as No. 2., but the 2nd. and 3rd. speeds are obtained by friction brakes the same as the Lanchester and Wilson gears. The heavy duty gears however in our scheme as positive, that is, the 1st. speed and reverse and the top speed are by jaw clutch, and in our case we control the whole by an electric relay motor and camshaft. Both these epicyclic gears should idle quietly and when on direct drive there are no gears revolving, so under all conditions they should give the maximum silence. In all our schemes we have left the clutch and its pedal exactly the same as at present. We think that we have done wisely in not attempting to fit the Wilson gear which we believe would not prove satisfactory to the owners of the cars under the service that they can demand, especially abroad. We do not believe that the Salerni arrangements will turn out sufficiently good to enable us to adopt them. The complete problems of Salerni couplings and their application under all the varying conditions appear to introduce complications which we cannot pass as satisfactory.. Regarding the spool gear this is undoubtedly more silent than the ordinary spur gears used in standard boxes, but there is no reason why this gear is easier to change than other gears of the same ratio, size of clutch and percentage of backlash being equal in all cases. They have however quite recently, we hear, adopted the Maybach type of backed off clutch which seems to make for somewhat smoother and more certain engagement - (quite an old scheme with constant mesh gears.) The spool gear however in our mind has not sufficient virtues to suggest its adoption, one reason being that there are 3 gears always running when idling or when on top, which we think very undesirable on a silent car. The other 2 gears we know of are the Studebaker, which Derby attempted to bring here but it failed before it left London, and the synchronous mesh, but this latter is the property of General Motors and is generally applied to the 3rd. speed only. We expect this has not proved altogether successful as they are cutting out some of the automatic proportions of it. R.{Sir Henry Royce} | ||