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 the mechanical operation of a steering wheel-mounted direction signal switch with a self-cancelling mechanism.
| Identifier | ExFiles\Box 113\3\ scan0145 | |
| Date | 15th January 1940 guessed | |
| - 6 - The switch and turn off mechanism are contained in a housing just below the steering wheel hub, and the wiring concealed by a metal cover which surrounds the steering gear mast jacket and transmission control shaft. The manual control lever has been placed on the right hand side of the steering wheel just above the transmission shift lever. This position was considered to be most desirable, because, both levers can be operated without removing the left hand from the wheel. When a right turn is anticipated, for example, the direction signal lever is moved in the same direction that the wheel will be moved when the turn is made. With the lever in this position, it is possible to move the steering wheel through an angle of approximately 106-degrees to the right, and 77-degrees to the left. These are compromise angles arrived at experimentally to enable the driver to maneuver the car through traffic to the right hand position for turning. In shifting the lever to this position a double pawl is placed in position to engage with one of two notches on a frictionally driven cam attached to the mounting hub of the steering wheel. In rotating the wheel for the turn, the pawl snaps over the notches in the cam, but as soon as the turn is made and when the wheel rounds up, the cam notch engages the pawl and results in rotating the switch lever back to a neutral position where it is held by a suitable detent spring. In this position the pawl is completely disengaged from the cam. It will be noted that when the lever is set for a turn, the angular rotation of the wheel before engaging the pawl is greater in the direction in which the turn is to be made. This serves the purpose of throwing off the signal, if for example, a left hand turn is made with the lever set in the right hand position. The friction clutch serves to protect steering gear action from any possibility of jamming that might interfere with steering operation. It also serves the additional useful purpose of permitting the switch to be timed correctly with relation to the straight ahead position of the steering wheel, without the use of tools. Figures 5, 6, 7, and 8, illustrate the method of timing the switch. Figure 9 illustrates the general construction and assembly of the control switch. In concluding this paper, may I ask your further kind indulgence for a few minutes to view some colored movies that have been made to illustrate the several types of signals that have been referred to, and the manner in which they operate. It has been difficult to secure good photographs of the signals in operation in the limited amount of time available for this purpose. It is hoped, however, that they may be sufficiently clear to serve the purpose. | ||