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).
Description of an automatic overdrive unit, explaining its operation and components with diagrams.
| Identifier | ExFiles\Box 125\2\ scan0115 | |
| Date | 2nd November 1936 guessed | |
| made in the past to solve this problem by such means as the addition of another manually shifted gear set in the transmission or by two-speed rear axles. In every case, these previous attempts have failed because of noise, or lack of automatic control, which permitted driving the car in the wrong gear at the wrong time. Chrysler engineering, after several years of intensive effort, is again a pioneer, this time in the adoption of the first successful answer to the overdrive problem, one which meets all the requirements of simplicity, quietness, reliability, and automatic operation. THE OVERDRIVE DESCRIBED Referring to the sectional view of the overdrive transmission, shown at the bottom of page 7 [Illustration D], it will be seen that when the mainshaft is in the position shown, the teeth on its right end mesh with both the free-wheel cam and the centrifugal weight assembly. In direct drive [Illustration B], the flow of power is indicated by the broken arrow, being from the mainshaft, to the free-wheel cam, through the rollers to the free-wheel housing which is integral with the tail shaft. The overdrive is obtained with planetary gearing and the shift is accomplished by centrifugal weights. A sun gear [Illustration A], is mounted on the case and is attached to the cushion hub which prevents it from rotating. [A] Automatic Overdrive Unit SUN GEAR, PLANET GEARS, RING GEAR - 6 - The sun gear is surrounded by five pinions or planet gears on needle bearings which are mounted in a suitable cage. The pinions mesh with an internal gear which is riveted to the tail shaft assembly. A notched drum is attached to the pinion cage. Examination of the gearing will show that in direct drive this drum rotates more slowly than the centrifugal weight assembly. Each of the two centrifugal weights is held inward by a coil spring until a speed of 45 m.{Mr Moon / Mr Moore} p. h.{Arthur M. Hanbury - Head Complaints} is exceeded. At this time centrifugal force overcomes the resistance of the springs and the weights tend to fly out. However, the outer surfaces of these weights are so curved that they cannot enter the notches as long as they are rotating faster than the drum. But just the instant the foot is lifted from the accelerator pedal, the engine, mainshaft and weight assembly slow down together. As soon as their speed reaches that of the [B] Flow of Power in Conventional Drive— No Overdrive or Free wheeling [C] Flow of Power in Free wheeling [D] Flow of Power in Overdrive • 7 • | ||