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).
Vibration issues with the auto-switch and dynamo cutout due to high resistance and proposing connection alterations.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 133 | |
| Date | 11th November 1927 guessed | |
| -4- Contd. It was remarked in our previous report that with the old connection of the negative end of the shunt coil of the auto switch to distribution box terminal A a low frequency full travel vibration would occur with the high value of the resistance which we propose to adopt, the reason being that on the operation of the auto switch unit the E.M.F. of the dynamo is so much reduced that the cutout breaks the circuit, after which the dynamo voltage operative upon the auto-switch shunt coil is insufficient to maintain the contacts open. Consequently the sequence is repeated and a vibration both of the auto-switch unit and of the cutout occurs. This would also occur with the Midgley type of auto-switch if it was attempted to use a high resistance. We avoid this by altering the negative connection of the auto switch shunt coil to the earthed side of the cutout, and allowing the battery to hold the auto switch off contact until the main charging switch is put off. So far we have been mainly concerned with normal running circumstances, but if we now consider the open battery circuit condition, th and firstly without any load connected, then, even with the connection as we have it, a low frequency full travel vibration of the auto switch occurs, and at the same time the cutout also vibrates. At all except high speeds the maximum momentary voltage of the unloaded system is prevented from rising above the figure at which the auto switch operates. Moreover, the effective average voltage of the system is several volts less than this, because of the | ||