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).
The merits of 3-speed versus 4-speed gearboxes, considering performance, cost, and petrol consumption for a small car.
| Identifier | ExFiles\Box 137\5\ scan0006 | |
| Date | 2nd February 1919 | |
| Contd. -2- EH3/LG12.2.19. hills, it would be very unsatisfactory to have to use that gear mile after mile on reasonable gradients. I do not feel happy with the idea of overcoming the difficulty by means of a lower gear back axle so as to be able to reduce the steps between the gears. We have got Dr Campbell Thomson's car running about with the low gear back axle and this car is notoriously bad for petrol consumption. Our cars with the present gears in France are often run up to 70 to 75 M.P.H. (and customers demand this speed) this means 2300 to 2500 revs. One does not like the idea of the engine on a touring car running any faster than this. As regards the reduction in weight between a 3-speed and a 4-speed box, it does not amount to ¼ of 1% on the car. The reduction in the number of pieces would be less than 1%. As regards the increased cost, I consider the amount would be saved in the reduced petrol bill for a months tour. My opinion is that if one is considering cheapness, quantity production, or looking for any easy way to overcome difficulties, that a 3-speed gear box is the best proposition but if one is out to make the best car which can be used in any part of the world, then a 4-speed box is the best. I think these arguments apply to the small car, in fact I am of the opinion that 4-speeds are most essential on the small car if it is going to be capable of doing any kind of work. The man of moderate means who will buy the small car and in most cases drive himself, will be very keen on the petrol consumption. I think it would be unwise to do anything which will tend to make the petrol consumption worse - what with high cost of petrol and | ||