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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 The B.T.H. Co. Ltd. answering queries about a distributorless magneto for a 20 HP car.

Identifier  ExFiles\Box 57\2\  Scan248
Date  7th May 1928
  
X.5790

EFC7/T.

7th May, 1928.

Messrs. The B.T.H. Co.Ltd.,
Alma Street,
Coventry.

Dear Sirs,

Distributorless magneto for 20 H.P. Car.

We thank you for yours of the 18th ult., and regret that through an oversight this has not been answered before.

The answers to your queries as numbered, are as follows :-

(1) The timing range called for is magneto timing range.

(2) The magneto is to give two sparks per revolution corresponding to 1 1/2 times engine speed.

(3) The existing coil ignition distributor head is used for distributing the high tension output of the magneto as an alternative not simultaneous method of ignition. This distributor head has incorporated with it a contact breaker for the coil ignition which is not in use when the high tension output from the magneto is fed to that distributor.

Concerning your reference to your distributorless pattern "CE" inductor magneto, the timing range of which could be 22 1/2°, presumably this machine is a four spark per revolution type, giving an equivalent range of 45°. We fear however, this would not meet the case, because of the different speed of driving, the same drive having to drive the dynamo. In regard to the automatic timing devices, we do not at present entertain the fitting of anything of this type.

Yours faithfully,

FOR ROLLS-ROYCE LIMITED.
  
  


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