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).
Design challenges and mechanics of a new epicyclic gearbox scheme, focusing on gear meshing and speed synchronization.
| Identifier | ExFiles\Box 6\2\ 02-page159 | |
| Date | 3rd April 1931 | |
| HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} ) FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} MOR. C. to R.{Sir Henry Royce} PN.{Mr Northey} DOUBLE TOP OUR EPICYCLIC SCHEME. This being quite a departure we must expect much trouble before it is right. Since we are changing without taking out the clutch the pinion will be forced to revolve in one direction or the other according to the difference in the speed of the engine relative to the car. As the load on these jaws is light the speed will be great - i.e. pinion restless but fairly easily brought to rest. since it has to alter the speed of the engine it may need one third over-running torque to bring it to rest. So that the difference of speed is 3 times as great as on an ordinary box. We shall probably not mesh so easily in this kind of meshing but we can brake control or syncro-mesh more easily, and apparently we need not do this changing into top because the engine is dropping down-rapidly naturally to synchronising speed whilst the throttle is closed and the pinion starts from rest and increases in speed as the engine decreases in speed. in this case the ratchet jaws would see that it never goes faster than the engine revs., at which speed it would mesh with almost any type of jaws. A Salerni ring would make it silent. Now the pinion need never go backwards so it could have silent ratchet or free wheel device to control it that way, and also synchro-mesh is easily arranged by cone, plate, or band brake bringing the pinion to rest. It will be seen that these devices always have to alter the engine speed (but can do fairly easily, much more so than by the ordinary type.) When the difference in speed is not great and there is some slack or spring in the transmission they may go in with a click and a shock which one may not feel. Maybach may work this way and we may not because our difference in speed is greater. Our loads are much less - i.e. 1/3rd. engine torque instead of 1-1/3rd. & 4/3rds. engine torque. If as I imagine getting into top does not give much trouble we can spend our energy trying to get into 3rd. this I expect will cause some redesigning work. Salerni shewed us that there seems little harm (and no noise with his scheme) if we contented te- ourselves | ||