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).
Analysis of various automatic and manual turn signal mechanisms and their effectiveness.
| Identifier | ExFiles\Box 113\3\ scan0144 | |
| Date | 15th January 1940 guessed | |
| - 5 - (2) Time controlled relays in which the signal is turned on manually when approaching a turn, and after a predetermined lapse of time turned off automatically. (3) Semi-automatic types in which the signal is turned on by the manual movement of a conveniently located lever, and turned off automatically by the steering gear mechanism after the turn is completed. (4) Full automatic and manual combination. This type can be turned on manually when approaching a turn and, if not turned on manually, will operate the signal while the turn is being made, and turn off the signal after the turn has been completed. Experience has shown that the undesirable feature of the straight manual type is that the driver frequently forgets to turn it off. This confuses other drivers and may add hazards rather than remove them. In a thorough study of various mechanisms, the following was concluded: (a) - Straight manually controlled devices are unsatisfactory. (b) - Straight time controlled relays offer some advantages over manual operation. Driving conditions, however, vary the time required. Thus, if the time is sufficient for signalling a sufficient distance before making the turn when driving at a normal rate of speed, the timing will not be correct if the signal is set while the car is idling at a street signal where the turn is to be made. Thus, the signal may continue to flash long after the turn is made. Systems have been advocated in which this condition is taken care of to some extent by controlling the timing device thru the engine vacuum. Experiences with several devices of this type have revealed many short comings. The ideal system would be one which would be entirely automatic in its operation, except there is no device that can anticipate the drivers intentions. (c) - An automatic system that functions as a result of movement of the steering apparatus does not allow sufficient time for those following to anticipate the drivers intentions. In fact, by the time the signal operates it is already apparent by the movement of the car that a turn is to be made. When such a system is combined with manual operation there is a definite tendency for the driver to neglect the manual setting and depend entirely upon automatic operation which, as has been pointed out, is unsatisfactory. There is one additional objection to mechanisms that turn on automatically from steering wheel rotation. If such devices are made sufficiently sensitive to close the signal circuit with the initial movement of the wheel, this occurs also when the car is being driven through traffic in passing around other vehicles. This tends to create confusion and may result in many people ignoring direction signals altogether. After carefully analyzing the requirements, it was decided that a system which could be turned on manually by the driver, and turned off by steering wheel action after completion of the turn, would offer the best compromise. Accordingly, a system of this kind was developed. The following brief description of the construction and operation of this switch may be of interest. | ||