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).
Controlled differential and epicyclic steering systems for tracked vehicles.
| Identifier | ExFiles\Box 144\4\ scan0188 | |
| Date | 10th December 1940 guessed | |
| 6. gearbox in that when one of the steering brakes is locked the two half shafts are obliged to run at speeds differing in a fixed proportion, resulting in a fixed turning radius. Radii greater than this can be obtained by slipping the steering brake. Unlike the double gearbox, sharper turns cannot be obtained which is a serious limitation. This system is mechanically slightly simpler than the double gearbox, gives a poor minimum turning radius and does not allow a compact arrangement of the transmission in the tank. 5. Controlled Differential & Controlled Epicyclic. These systems are identical in principle. Assume that the main gearbox is in neutral so that the main drive is not rotating. If the supplementary drive is now rotated, one track sprocket will be driven backward slowly and the other forward with the result that the tank will turn about its vertical axis. The direction of rotation of the supplementary drive determines which way the tank turns. If the main drive is now rotated, forward motion of the tank is superimposed on the turning motion and the tank will proceed in a curved path. The higher the speed of the main drive, the greater the radius of the turn for a fixed supplementary drive speed. In practice the supplementary drive would be taken from a part of the transmission running at engine speed by a pair of controllable slipping clutches, one for each direction of steering. The important feature of this general method of using a supplementary drive is that full engagement of a steering clutch or brake results in a turning radius which becomes progressively smaller as the main gearbox is changed to its lower ratios. This is very closely what is required in operating the tank as obviously tight turns cannot be made at high speeds, but are required at low speeds. In consequence, the steering clutches can be so geared that the amount of power wasted in them is greatly reduced and roughly a 75% improvement over the plain differential is obtained in this respect. -Continued- | ||