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).
Technical memorandum detailing the specifications and modifications for the Spectre Gearbox.
| Identifier | ExFiles\Box 94\1\ scan0001 | |
| Date | 21th April 1934 | |
| COPY 328 To DY{F R Danby}, from HSY. c. For. Mr. Hs.{Lord Ernest Hives - Chair} Po. RHO. HDY.{William Hardy}1/HP.21.4.34. GRY{Shadwell Grylls} SpectreCodename for Phantom III Gearbox. We are sending herewith N. Sch's 4027 and 4029 which show the gears, shafts and bearings for this box, which is a J.3. box with various modifications. The ratios we propose are:- 3rd .755, 2nd .507, 1st .355, and R .355. As shown, the 1st and R.{Sir Henry Royce} gears have straight teeth but we are proceeding with the application of helical teeth to these gears and for this reason, the rear half of the casing is shown in a temporary form where it is modified to accommodate the 2nd speed gears which have been made wider, as there will no doubt be further modifications to make later. All the helical gears are 25% wider than for J.3, have a D.P. of 10 and obliquity of 20°. To enable wider gears to be more satisfactorily used the layshaft has been increased in stiffness by making it of the same dimensions as the 3rd motion shaft. The 1st speed gears are 12% wider than the J.3. gears and are now 7 D.P. with .040" correction to enable the larger shaft to pass through the 15 tooth pinion. The helical gear 1st speed scheme will probably be free from the limitations which we now have on the travel of the 1st speed pinion and we shall be able to further increase the width of these gears if we wish to without reducing the leverage of operation of the 2nd speed S.M. clutch. The shaft centres have been increased from 3.500 to 3.570 to enable the reverse pinion to clear the 3rd speed pinion without increasing the length of the box. We have made the sleeve for the 2nd speed S.M.clutch the same diameter and thickness as that for the top and 3rd | ||