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).
Gearbox design alternatives, including epicyclic trains, clutches, and gear ratios.
| Identifier | WestWitteringFiles\U\2January1930-September1930\ Scan091 | |
| Date | 3rd September 1933 guessed | |
| (2) Since however we can now easily go to 2nd. perhaps we can keep 3rd. also fast, and I think the 4 trains make the most silent and easiest made job, especially as all the planets can be large and slow speed, (and still give a ratio not less than .72) and the upper ones narrow and fine pitch so that they need not weigh much. Mr. Hardy's alternative of the bevel .5 is perhaps the best alternative to get the 3rd., but this type of gear is costly to get right;compared with stringing a lot of parallel gears on the shafts it is not good for production. The following summary may be useful:- (1) Having an easily available 3rd. the top gear can and should be higher, to avoid over-running the engine, fuss, and bad petrol and oil consumption. An undergeared car is not pleasant. With our latest RRs., especially 'twenties', I often attempt to change from top to something higher. (2) It should be realised that my suggestions avoid the high torque brakes that are necessary for Wilson/Lanchester scheme, by using a positive 1st. speed and reverse, so that if we use brakes on the 2nd. and 3rd. they will only need to have 1/1 engine torque, and 1/2 engine torque respectively, instead of 2 and 4 times with the Wilson/Lanchester gear. (3) We can use either jaw clutch or friction clutch of 1/3rd. engine torque for top gear. I should design for the latter if we use the control suggested in this memo. (4) For the 1st. speed my idea is to use silent ratchets to hold the annulus controlled by light brake. (5) For reverse we should use gear type jaw clutch (like direct drive present box) to hold planet cage (this type for safety.) (6) For simplicity, and for a trial, we may obtain our neutral by letting the reverse run idle. (7) The side lever should have forward, neutral, and reverse, so that one gets a neutral in each gear by this lever, and the car will be driven forwards or backwards by whatever gear train is in, but the reverse will always be at about 2/5 of the forward speed. (8) The proportion of all the 5 epicyclic trains, including reverse, I should prefer to be - annulus 100, sun 40, planets 30 and 3 planets. The width will vary with the maximum load, and the 1st. and reverse can be loaded nearly as high as an ordinary box. The pitch could be coarse on the wide 1st. train, and finest on the 3rd. speed train, which has to run backwards at rather high speed while 1st. is driving the car with high engine revs. Experience would soon say if | ||