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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).
Serious failure of a Dynamo Voltage Regulator on Sir Edmond Crane's car, GRF-9.

Identifier  ExFiles\Box 166\2\  img021
Date  14th November 1935
  
BX.
Hs.{Lord Ernest Hives - Chair}
S.
Wep.

86092.

Hd{Mr Hayward/Mr Huddy}/SB{Mr Bull/Mr Bannister}27/HR.14.11.35.

Re DYNAMO VOLTAGE REGULATOR.
---------------------

We have to report a rather serious occurrence on Sir Edmond Crane's car, GRF-9. This car came here for a de-carbonisation and tune up and attention to the brakes and clutch.

Whilst the car was on test last night after the repairs had been carried out, there was a strong smell of burning under the bonnet. Immediate investigation showed that the resistance unit adjacent to the voltage regulator was white hot and had burnt a hole right through the Bakelite base of the regulator unit and through the Bakelite cover.

There had obviously been such an intense heat that there would undoubtedly have been a fire had there been anything inflammable nearby, as would have been the case on the Bentley.

Of course, the parts concerned have been so badly burnt that it is almost impossible to carry out any tests on them, but the following points seem clear and we think, call for attention to prevent recurrence.

In the first place we find that this resistance unit will become white hot when passing between 3 and 4 amps, whereas the field fuse does not blow under 4½ amps. In other words, there is no protection against a fire in the event of there being any fault in the regulator which permits a current of 3 amps to be passed through the resistance.

It would appear that such a state of affairs can occur when the regulator unit sticks in such a position as to leave the resistance unit permanently in circuit.

This seems to be what has occurred with this particular regulator.

-contd-
  
  


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