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 discussing experiments to fix the 'creeping gears' issue in the India 4-speed gearbox, focusing on spline angle and parallelism.
| Identifier | ExFiles\Box 6\4\ 04-page134 | |
| Date | 21th May 1925 | |
| To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. Wor.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} SECRET X.5310 R2/M21.5.25. 'INDIA' INDIA 4-SPEED BOX. X.5310 The other day I wrote to you about making experiments to see the cause of the creeping gears. Some of the experiments I suggested appear unnecessary, and perhaps we could simplify them as follows :- Any shaft you make should be parallel. The shaft that has been adopted is when carefully measured 45° driving angle of splines. This is the angle to a radial line. You will remember that I suggested we should try all the angles between 15° and 60° It now appears unnecessary to go beyond 45°. It is still mysterious why the other 45° splines were not a success, and I can only explain it as follows :- The splines cut in the gear on the slotter are not parallel in the bore and they give a tight band somewhere near the middle of the pinion. I therefore suggest that we alter some of the gears as shown on Lec. 3071. (attached to BY's copy) herewith. Here the driving teeth are directly under the gear if the gear is only half engaged: if fully engaged it is a little bit out of centre. My impression is that this gear will stay in especially if the bore is a little larger at the engaged end, and one feels sure that the moving gears have been caused by splines not carrying the gears directly under the teeth, which are loaded. If they are ever so slightly tapered the end of the pinion will move about, in which case it may creep either in or out, so that all the shafts will be made parallel, and some of the experimental gears will be made parallel, and some taper, on the spline driving faces. The length of the splines in the above will be cut down until the keys are quite short, and opposite the driving forces. Our drawing shews an approximate cylindrical fit at the threaded end of the pinion, and the keys extended as far forward as possible. It may be that there Keys will be found too long. You will see that the tendency from the earliest instruction has been to get the keys tight right under the gear, and to increase the angle of the driving faces until the torque will centralise the gear against any disturbing force. It would appear that the square and hexagon shaft, and the larger dia. pinion could all be made satisfactory. I shall be pleased to have a report on your experience. contd :- | ||