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).
The principles of a cam and peg gear shifting mechanism, including self-selection.
| Identifier | ExFiles\Box 147\3\ scan0134 | |
| Date | 24th August 1938 guessed | |
| CAM AND PEG MECHANISM. Long experience has proved that a cam and peg mechanism provides an easy and reliable method of shifting the gear members. Motorcycle gears (of which very many thousands have been made to my designs) almost entirely depend on this method of engaging and disengaging the gears and these gears are famed for their easy rapid changing. It should be noted, however, that the cam and peg used in this control are employed only for the relatively light job of shifting the gears into neutral, which it can do with ease and with the certainty and precision this operation demands. In addition, without adding any parts to the mechanism, the cam provides a strong lock for the gears both in neutral and in-gear positions. See Fig. 8a on print. The cam contour is formed to suit the particular method employed to operate the mechanism; for example in clutch-pedal control the cam can be shaped to allow the control shaft of the mechanism to make a partial turn without disturbing the pegs and shift forks during clutch operation, in place of or in addition to the 'interval' provided in the coupling for this purpose. A further use of the cam is mentioned under the heading "Clutch-pedal Control". Gear Striking Levers, Coupling Pawls, etc. These require no special mention as they are simple robust parts of the kind that function almost indefinitely with very little attention. As the mechanism is enclosed with the gearing it is always well lubricated and is likely to last as long as any other working part. SELF-SELECTION OF THE GEARS. This seems the obvious development of preselection and it makes getting away easier quicker and safer as the driver, not having to bother with any kind of gear lever, can keep both hands on the wheel and give all his attention to road and traffic just when a little extra care is often needed. As this getting away after stops accounts for a large part of our gear changing it saves much time if we can get through the gears easily and quickly. | ||