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).
Letter discussing a new 'selector' shift gearbox, ideal axle ratios, and a torque-equalized brake system.
| Identifier | WestWitteringFiles\U\August1930-November1930\ Scan072 | |
| Date | 6th September 1930 guessed | |
| Oy-l -2- no charge. Both schemes and the actual box will be fitted with the new "selector" shift which is a development of the Maybach clutch, similar to the Salerni coupling, but simpler in application. This means, that the dogs are backed off in a direction to prevent engagement until the speeds are synchronized and the shifting means is provided with a spring device which will prevent the non-engagement of the dogs from vibrating the hand of the driver. This appears to be the final answer to the objection of "thumping" engagements, particularly when shifting down on the internal gearbox. It is similar to a free wheel in some respects, but much simpler. (See sketch). In applying this box to say the 25 HP., their recommendation for "ideal" results is as follows:- Raise the axle ratio from say 1 to 5 to 1 to 4 choosing the new ratio so that, when the engine power-curve is "written down" 10% to allow for "lack of tune" after a year's use, the peak of the power curve lies on the curve of power required with a body of average wind-resistance. Supposing this "ideal" axle ratio turns out to be 1 to 4 Third gear will be .7 of this giving a virtual ratio of about 1 to 5.6 which is ideal for (American) city driving. Second gear is used for starting. Brakes. The following will interest you. A brake has long been under development which is "torque equalized". I wrote you about this some years ago. The brakes on either end of the axle are so arranged, the anchorage pins being interconnected, so that neither of them can deliver more torque than the other. Hence, equal braking - lack of skidding, etc. This is developed for four-wheel applications. Now it is further developed as an automatic brake adjustment, so that the same mechanism which balances the torque also keeps the two brakes set up "on a torque basis" (just as they would be adjusted by say a garage with a fourwheel Bendix-Cowdray brake tester.) A by-product of this scheme is to make any servo action on the average passenger car unnecessary since the whole of the pedal-travel can be used for leverage, without any allowance for wear of the liners. I haven't thought much about this, but it seems interesting, and if I can find anything more about it, and if you are interested, will write you. Yours very truly, | ||