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).
Continuation of notes on the Packard gearbox, with comparisons to Lincoln, and a section on Packard valve springs.
| Identifier | ExFiles\Box 173\4\ img230 | |
| Date | 5th December 1935 guessed | |
| Packard Gearbox Continued. On the teeth they remove approximately .003 from the tooth face on the drive side, so as to make this action all recessive. On the over-run the tooth has a full face. They prefer what they call fine pitches 10's con. mesh and 8's on 2nd. speed train. They find the fine teeth with extra length strong enough. The angles of their cones are 5º and 6º and are very small. They use no locking cam on the big car but only plungers. However, on the 120 they have gone to a locking cam. The big box could be crashed, but not so easily as the Lincoln. The movement of the ball on top of change speed was kept down by the engine mounting which is so arranged that the axis of torsional flexibility passes through the top of the gear tower. The movement under full torque was really very little. The splines they use are involute stub teeth, a full number corresponding to the P.D. and S.P. The Lincoln boxes were both very noisy. But in the silence room the big box was extremely quiet, so that the boxes appear to be noisier in position on the car than when being tested for silence. The splines are involute teeth, but only six of them instead of a full number. both cars chunked. Both Lincoln gear boxes could be easily crashed. They also had no locking cam. Valve Springs. Packards use a straight carbon steel (.650 or .900 they were not sure which) and kept the maximum stress down to 72000, with a range of 25%. This arose in connection with Bentley valve springs breaking in America. | ||