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).
Alternative gearbox designs, including epicyclic units, freewheels, and their controls.
| Identifier | ExFiles\Box 15\5\ Scan055 | |
| Date | 12th November 1928 guessed | |
| contd :- -2- sliding these, or continual mesh, with jaw clutch and freewheel side shaft, and also of a still higher 3rd. ratio to be more useful and easier to get into. (There are no doubt top speeds as far as we know - Graham-Paige and Voisin are both indirect on third.) We have also in hand a much more drastic way of providing both a still more accessible and extremely silent 3rd. gear. This is by the epicyclic unit as 3rd. speed, in such a way that in conjunction with an ordinary small 2-speed gearbox, 4 speeds are available (patented by us many years ago). I have now schemed a combination of this idea which we think has superior merit to anything at present offered. The difference is that the usual clutch is retained and is used in the usual way for all gears, i.e. the epicyclic unit is not used as a clutch for starting the car, or while the car is idling, therefore some of the difficulties of the more usual arrangement of gears running while idling is avoided etc. The 2nd. and extremely valuable point is that used in conjunction with a positive (usual) box for the low speed and reverse we have only to deal with light torques on the epicyclic unit's special clutch and brake (necessary feature for easy and smooth change). These forces are only about a quarter and a third engine torque (instead of 2 to 4 times.) The 3rd. still more valuable point is that in our scheme the change from or to 3rd. speed can be made without touching the clutch pedal, and without closing the throttle, gaining precious time and not upsetting the continuous carburation etc. of the engine. Our scheme includes a small hand operated valve which controls the oil (pressure) flow to the operating cyls. (oil relay). For extra silence the epicyclic unit has been designed with helical gears. This unit can be compounded in several well known ways if desired to give another speed, or for reasons of silence etc. It can be located between the engine and main clutch or between the clutch and the ordinary gearbox; the latter seems the more convenient position. Any failure of the operating oil will not prevent the car being driven as an ordinary car with two speeds only. A freewheel anchorage can be used instead of the brake for the sunwheel of the epicyclic unit. The controls can be arranged to be direct operated, or by any other type of relay - compressed air or friction servo. R.{Sir Henry Royce} | ||