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).
Analysis of tank transmission and steering systems, featuring the Merritt Brown System.
| Identifier | ExFiles\Box 144\4\ scan0189 | |
| Date | 10th December 1940 guessed | |
| 7. So far as we can see up to now, the complication and cost of these systems is approximately the same as the double gearbox, the weight should be less and the performance better. 6. Merritt Brown System. This is a comparatively recent design, and is fitted to an experimental 35 ton tank now being developed. The diagram shown on Rm.{William Robotham - Chief Engineer}662 looks very complicated, but this is because the main gearbox has to be shown to illustrate the system. The principle of the system is identical to the controlled differential and controlled epicyclic and the design merely amounts to one of the many possible ways of arranging the layout. There are three points about this particular layout which should be noted. (a) The supplementary drive for the steering is taken from the gearbox shaft connected to the main engine clutch. (b) The gearbox is arranged to run at a low speed so that it is large and heavy for the power transmitted. (c) When the main gearbox is in neutral, the tank is driven backward by the supplementary steering drive. This saves a reverse ratio in the main box but makes it impossible to turn the tank about its vertical axis without fore and aft movement. From the above descriptions of the various steering systems, it will be seen that they all involve a form of slipping brake or clutch and overheating of this appears to be a heritage of most tanks. This clutch is in much more continuous operation than the brakes of a car as even when driving along a straight cambered road the clutch has to counteract the drift of the tank down the camber. Owing to this, we consider that the important feature of this unit is its rate of dissipation of heat rather than its capacity for storing it. Our main criticism of existing steering clutches or brakes is that they invariably run at low speeds of 250-500 r.p.m. and are consequently difficult to cool. A further point is that the higher the maximum speed of the tank, the greater the work to be absorbed by the steering clutch. This comes -Continued- | ||