Rationale for fitting overdrive gearboxes to Phantom III and Wraith models.
| Identifier | ExFiles\Box 8\11\ 11-page094 | |
| Date | 8th September 1937 | |
| OVERDRIVE GEARBOXES. The primary object in fitting an overdrive on the P.III is to increase the life of the big-end bearings. The fitting of such a gearbox to a car immediately demonstrated the pleasantness of a very high top gear, due to the absence of engine fuss. This is particularly noticeable on the Continent. The R.R. overdrive arrangement of a 3-speed box and indirect high gear does, therefore, provide something the customer will like. We think, however, that the success or failure of the schemes depended on a very nice point; viz., whether satisfactory starts from rest could be made on the middle gear which was necessarily higher than the usual 2nd gear. On P.III the experiment has succeeded. Sometime ago we fitted a 3-speed arrangement to Sg {Arthur F. Sidgreaves - MD} 's car GLG.5. Not long afterwards, he asked us to change back to 4 speeds, which latter he preferred. We still have the parts in question, and are going to fit them to our 25/30 car 22.G.V. for a further test. The torque weight ratio of a 25/30 or Wraith is greatly inferior to a P.III. A satisfactory get away will not be possible on a gear higher than the normal 2nd speed. This means that the next gear below direct top will be the normal 2nd speed, i.e., 3rd gear will be missing. No one will like this. The usual "unditching" 1st speed is necessary whatever the other ratios, Possibly Continental customers would put up with starting in 1st speed in order to have an overdrive, but we think the majority of owners would prefer the present 4 speed box. The object of this memo is to explain why we shall be selling simultaneously a P.III with an overdrive, and a Wraith without it. | ||
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).