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).
Issues with the Spectre Gearbox reverse shaft and proposing modifications to the gear angles.
| Identifier | ExFiles\Box 94\1\ scan0032 | |
| Date | 21th September 1934 | |
| X4094 32S GRY{Shadwell Grylls} To MHC. from HDY.{William Hardy} c. Mor. S. Hs.{Lord Ernest Hives - Chair} Ey. De. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} SpectreCodename for Phantom III Gearbox. With reference to the reverse shaft of this box, we have this morning witnessed tests of the helical angles of the two gears on the shaft and are satisfied that the cause of the shaft working out of mesh is not that the angles of the gears are incorrect to the drawings. Our opinion is that the probable explanation is that the drag of the plain bearings of the shaft, and to a lesser extent the friction of the teeth, destroys the balance of end load sufficiently to overcome the plunger spring. The friction will be a varying quantity and it is evident that we cannot arrange the gear angles to give a perfect balance always, but we can arrange to have a surplus of thrust which will be always in the direction of moving into mesh and a plain thrust face will take this quite moderate thrust. Existing Gears. Our proposals are that for the existing SpectreCodename for Phantom III box we reduce the helical angle of the large gear on the reverse shaft marked 'A' on G.81578 by 38'-4" making the new angle 32°50'. This means that 8/1000" is removed from the tooth face at one side. Both sides of each tooth are ground to the new angle and as the mating gear on the layshaft is similarly treated there will be an increase of clearance of 16/1000" between the teeth. With the above modifications the reverse shaft should stay in mesh on the drive unless the bearings are tight but may come out on the over-run. | ||