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).
New 'Double Top' epicyclic gearbox scheme, its potential issues, and comparisons to other designs.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan093 | |
| Date | 4th March 1931 | |
| HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} ) FROM R.{Sir Henry Royce} (HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} is crossed out) BY.{R.W. Bailey - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) (BY.{R.W. Bailey - Chief Engineer} is crossed out) ORIGINAL R1/M3.4.31. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} (SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} is crossed out) C. to E.{Mr Elliott - Chief Engineer} PN.{Mr Northey} (E.{Mr Elliott - Chief Engineer} PN.{Mr Northey} is crossed out) DOUBLE TOP. OUR EPICYCLIC SCHEME. 8523. x7310. 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 our difference of speed is 3 times as great as on an ordinary box. We probably shall not mesh so easily in this kind of meshing but we can brake control or synchro-mesh more easily, and apparently we need not do this changing into top because the engine is dropping down naturally to synchronising speed while 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 should mesh with almost any type of jaws. A Salerni ring would make it silent. Now the pinion never need go backwards so it could have silent ratchet or freewheel 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 so fairly easily, much more so than 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. [STAMP: RECEIVED A.W.E. 1931] Salerni shewed us that there seems little harm (and no noise with his scheme) if we contented ourselves to wait until the engine is accelerated before we coupled up to drive the car or for the car to drive the engine. So that one could get our change to 3rd. by closing the throttle but we should expect to go on clicking (with Maybach) until we again opened the throttle. It occurs to me that face jaws might work equally well as Maybach. The corner we wish to over-run could be rounded more or less according to experiment and the corner we do not wish to over-run left square. R.{Sir Henry Royce} | ||