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).
Technical description and analysis of the 'Spontan' transmission system, detailing its operation and performance characteristics with graphs.
| Identifier | ExFiles\Box 41\4\ Scan042 | |
| Date | 21th September 1931 guessed | |
| PAGE 14 SPONTAN sleeve turns in the same direction as the engine. Fig. 6 shows the torque impulses acting on the main sleeve when the propeller shaft is running at half the speed of the engine. When a negative impulse is followed by a positive one the main sleeve must be brought from rest to the angular velocity of the driven shaft before the inner clutch can transmit a torque, and therefore the action of the clutch is somewhat delayed due to the inertia of the sleeve. Similarly, at the beginning of a negative impulse, no torque can be transmitted to the pendulum wheel until the sleeve has come to rest and therefore, as shown in Fig. 6, there are two periods in each revolution in which no torque is transmitted. Fig. 7 shows, at the given speed ratio, the torque impulses acting on the propeller shaft flywheel and the smoothening action of its inertia, the slightly undulating curve representing the turning moment after the flywheel. The direct engine torque is also plotted and the difference between the actual torque and the engine torque represents the increase in turning moment produced by the action of the weights. The utilization of this additional torque is made possible by the fact that its reaction is taken on a stationary point, in this case on the gear casing by means of the pendulum wheel springs. When the transmission is working on "indirect drive" as now described, i. e.{Mr Elliott - Chief Engineer} when the engine is running faster than the propeller shaft, the torque on the propeller shaft is given by the fact that, frictional losses being neglected, the angular velocity multiplied by the torque must be the same on the two sides. As the car increases in speed, the positive impulses become longer and longer until finally the gear automatically changes over to "direct drive" as soon as the propeller shaft resistance has decreased to the value of the direct engine torque. During direct drive the bob weights are not rotating on their eccentric discs as these revolve at the same speed as the engine crank shaft. The main sleeve occupies such a position relative to the engine that the torque transmitted from the engine is equal to the resistance of the propeller shaft. PAGE 15 SPONTAN Variations in the propeller shaft resistance are dealt with by automatic adjustments of this relative position, a moderate increase of the resistance causing the main sleeve to lag. [Fig. 8 Graph] Tractive force at road wheels of a car with ordinary transmission. Cylinder volume 3680 c.c. Gear ratio 1:4.88/8.88/15.86 Fig. 8. [Fig. 9 Graph] Tractive force at road wheels of a car with Spontan transmission. Cylinder volume 3680 c.c. Gear ratio 1:4.88 to 1:infin. Fig. 9. behind the engine crank shaft, thus increasing the leverage of the centrifugal forces, until the transmitted torque has increased sufficiently to overcome the new resistance. If the increase is considerable, the drop in speed of the propeller shaft may be of such a magnitude as to make the weights revolve on the sleeve, i. e.{Mr Elliott - Chief Engineer} indirect drive is resumed. During direct drive freewheeling takes place permanently in the reaction clutch and, consequently, the pendulum wheel is out of action. A characteristic of the operation of this transmission both | ||