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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).
Letter to Messrs. North & Sons Ltd. regarding complaints and test failures of R.O.I. magnetos on a 20 HP chassis.

Identifier  ExFiles\Box 57\2\  Scan209
Date  29th September 1928
  
X5790

c. BY
c. Mailing.

EFCL/T.

29th Sept., 1928.

Messrs. North & Sons Ltd.,
Whippendell Road,
Watford.

Dear Sirs,

The Test Dept. have once or twice had complaints of the R.O.I. magnetos on our 20 H.P. chassis, and the following is a quotation from a report dealing with this matter:-

"We have had several complaints from time to time of the inefficiency of these magnetos.
Recently the Test Dept. have had one case where the magneto misfired under load and they stated that they had come to the conclusion that the safety gap on this magneto was too small.
The magneto in question No.105629 has been lent to us for test and we have put it through a bench test to our General Specification of Magneto for 20 H.P. car.
We found that the magneto failed to comply with items 3, 6, and 8 on that specification. In the case of item 3, the safety gap length was unobtainable but we ascertained the breakdown voltage by using a parallel gap. The voltage at which the safety gap would spark over was found to be 9050 or 6400 R.M.S.
We noticed that the contact breaker was fitted with the old steel lever which we consider to be now obsolete as it contributes considerably to the noise".

It does not appear that these magnetos in general satisfy our General Specification of Performance of which we sent you a copy dated 29.3.28, and particularly in respect of the length of the H.T. safety gap.

It should be stated that there is an error in the numbering of the paragraphs of this specification, as there are two No.5 paragraphs. The number of the second "No.5" and each subsequent paragraph should be increased by one
  
  


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