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).
Gear ratios, weight saving, and the preference for a three-speed over a four-speed gearbox for a new chassis design.
| Identifier | ExFiles\Box 49\1\ Scan223 | |
| Date | 12th October 1920 | |
| Contd. -3- R18/G12.10.20. (2) In our new work we are expecting to get the back axle ratio proportionate to the weight approximately, so as to give for all cars equal acceleration, i.e. ft. per second per second, and that all cars will climb a certain grade on their direct drive (it is about 10% or 1 in 10 without changing). In addition to this we are expecting to get a distinct saving in weight for which we can safely allow 5%. We are expecting to get 10% more power at least for the same revs. 10%. Having these advantages we should be safe if our lowest gear had a ratio of .36 which can be obtained with a three speed box having a second speed of .66 of the top and a low gear about .55 of this; this is our intention. I am quite willing to take the advice of every-body [handwritten: better] but it is rather to be guided by the best experienced head, rather than the average opinion of a crowd, and also supposing we produce the best compromise for the purpose| which is what we are out to do, we must rather expect to lead than to follow. Now with our present knowledge and the scheme of chassis we are proposing to adopt, a three speed box has such great advantages in simplicity and neatness of control that unless one really needed the four speeds very frequently, if it would not pay us to make a four speed box, in fact if we were obliged to do so we shall be driven to abandon our scheme of chassis, and make something which we consider all-round very Contd. | ||