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).
Two-page description of the operation and features of the Spontan Braking System.
| Identifier | ExFiles\Box 41\4\ Scan047 | |
| Date | 21th September 1931 guessed | |
| [Page 24] SPONTAN as the pedal is further depressed, the resistance to be overcome by the foot gradually becomes less but never disappears. Hence the brake spring will automatically return the pedal to the brake-on position and apply the brakes, when the driver allows his foot to be raised by the spring. The pedal controls the throttle by means of the rod 35. When the pedal is depressed sufficiently for the brakes to be fully released the pin 30 catches the slotted end of this rod. A further depression of the pedal then causes the throttle to open to any desired extent. When the pedal is raised again a spring restores the throttle to its minimum opening for the adjustment of which the hand control is retained. [Page 25] SPONTAN THE SPONTAN BRAKING SYSTEM AS already mentioned, it is a feature of the Spontan transmission that freewheeling takes place in the inner clutch when the propeller shaft tends to turn at a higher rate than the engine. It is therefore not possible to utilize the braking power of the engine in the ordinary way i. e.{Mr Elliott - Chief Engineer} by making the car drive the engine with choked throttle, if necessary in low gear. This fact cannot, however, be regarded as a drawback, provided other means are employed to produce a braking effect which in respect of smoothness in operation and adequateness for long periods of application can be compared to that of the engine. Ordinary motorcar brakes could not be relied upon in this case as they become overheated in long down-grades. A new braking system has therefore been developed, the characteristic feature of which is an enclosed internal expanding brake situated on the propeller shaft. Due to the high speed of the propeller shaft this brake can be very efficiently cooled by air so as to enable it safely to control the speed of the car without danger of overheating even in the longest down-grades to be met with in any part of the world. For exceptionally steep down-grades, and for emergency purposes, the front wheel brakes are called upon in addition to the propeller shaft brake, the brake gear being so arranged that the front wheel brakes are set in action automatically when the limit of the propeller shaft brake's capacity for continuous braking is exceeded. The action of the front wheel brakes, although beginning later, increases at a higher rate than that of the propeller shaft brake, and when the brakes are fully applied, a greater percentage of the total braking power is allotted to the front wheels than to the rear wheels. This gradual transfer of braking power to the front wheels is an advantage of the | ||