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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).
Fault report on Dynamo No.171 from chassis CMK.40, detailing issues with brush fitting and commutator sparking.

Identifier  ExFiles\Box 57\2\  Scan061
Date  16th December 1926
  
To BY.{R.W. Bailey - Chief Engineer} from EFC.
c. SFT{Mr Swift}/Mr. Brock.

X5780do

EFC3/T16.12.26.

20 HP. DYNAMO NO.171 EX CHASSIS CMK.40.

This is a 29 commutator segment machine. As in the previous case, there are one or two minor faults which, however, would not account for the solder running.

(1) In fitting a new set of brushes, the negative brush has been inserted the wrong way round.

(2) There is evidence on the commutator of bad sparking which probably took place during open circuit running.

The insulation is O.K. as received, but broke down across the brush dust on the 200 volt test.

There would appear to be insufficient reason for the commutator solder having run in normal circumstances. In this case we definitely consider there must have been an open circuit or faulty external connection.

It would appear to be necessary that our outside men should be made more familiar with the necessity of putting in the brushes in such a way that the frictional drag on the brush, and the horizontal component of the pressure of the spring on the top of the brush, should act in the same direction. This is most essential in the case of the negative brush.

EFC.
  
  


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