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 discussing a mystery fault with the second speed of a 4-speed gearbox, suspecting shaft bending and proposing solutions.
| Identifier | ExFiles\Box 6\4\ 04-page094 | |
| Date | 7th March 1925 | |
| X. 5310 SECRET. R1/M7.3.25. To BY.{R.W. Bailey - Chief Engineer} HS.{Lord Ernest Hives - Chair} } FROM R.{Sir Henry Royce} AJS. INDIA c. to CJ. BJ. E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} RG.{Mr Rowledge} 4-SPEED BOX. X.5310 I have telegraphed Derby as follows :- "ROYCAR. DERBY. ALWAYS BEEN MYSTERY ABOUT SECOND SPEED WORKING OUT. SUSPECT SHAFT BENDING DUE TO SLACK IN CENTRAL BEARING. TEST WITH TAIL BEARING REMOVED. BORE OF DOUBLE PINION DISTURBING WHEEL ON SPLINES TEST WITH MORE CLEARANCE IN BORE TORSIONALLY FREE SHOULD CURE IF SLACK IN CONNECTION. OTHER SUGGESTIONS IN LETTER. ROYCE". I could never understand why this 2nd. gear was wrong as the conditions are more favourable than the 1st. in the 40/50. I now can see that if the shaft bends through want of alignment of the 3 bearings through slack or flexibility in the support of the central bearing the double pinion will be disturbed in such a way as to creep out. Therefore it seems as though we must make the central bearing with less number of slacks, and here I think it is different to the 40/50. Then to ensure against any trouble of moving gears we should make either (1) the solid double pinion more free in its bore so that it does not touch the shaft either in the bore or on the keys at the end which is idle, or (2) the torsionally free double pinion with some slack in the sleeve connection. Probably this is the simpler scheme. It would probably not need more than .005", and it could easily have .015". I am so convinced that the foregoing is the cause of this 2nd. speed fault that xx I will not write my other suggestions. In conclusion we ought to reduce the risk of bending the shaft to a minimum: perhaps it would be better in 2 sizes, thus :- SEE ORIGINAL FOR SKETCH. R.{Sir Henry Royce} | ||