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).
Secret memo on 4-speed gearbox modifications for India, discussing design changes and patentable features.
| Identifier | ExFiles\Box 6\4\ 04-page088 | |
| Date | 3rd March 1925 | |
| HS{Lord Ernest Hives - Chair} To BY.{R.W. Bailey - Chief Engineer} from RHR. ST.{Capt. P. R. Strong} c. to BJ. CJ. E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} RG.{Mr Rowledge} Mr. Claremont. X. 5310 S E C R E T. R11/M3.3.25. I N D I A.{Mr Adams} 4-SPEED BOX. We hope this is satisfactorily finished. The modifications are of the simplest kind, surprisingly so. The chief points about these troubles are that (1) to avoid a complicated eccentrically engaged reverse we schemed a novel arrangement and did not see its peculiarity of not being self binding and would therefore creep out or in gear according to variation of stiffness, fitting, etc. and (2) that to avoid a massive gearbox, cost, weight, and layshaft, we adopted our special 40/50 scheme gearxxx of sliding the small pinion under slightly different conditions so that these were also moving about on the splined shaft. The simple scheme of curing these you now know, but they took much thought and I am chiefly writing this parte to know if it is thought that these are patentable features of sufficient value to the Company to justify the cost of the patents. At least they ought to be provisionally protected in England so that we should not have to pay another patentee. They are :- (1) The relieved key so as to bind in each position symmetrically and under the forces. (2) The torsionally free double pinion for the same object and to obtain a self fixing bind. The object is to hold the sliding gears in mesh due to epicyclic or other creep on the shaft, due to the tooth friction, and it also prevents biting in, or wear due to the minute movements in the box of the gears, owing to the unavoidable slack in such sliding gears. To finish this gearbox modification there is the addition of some substantial bosses for the front brake equal-ising shaft for N.sch.1939., which is approved. It will be remembered that to meet the impression of a somewhat slower 3rd. speed which is thought desirable, we have speeded the 2nd. motion shaft by one tooth, and to strengthen the 1st. speed and reverse we have added one tooth to these but these ought not to affect output, the bosses for the brake shaft being the modification causing any delay. R.{Sir Henry Royce} | ||