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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 from Lodge Plugs Ltd. regarding the testing of a returned Model X335 spark plug.

Identifier  ExFiles\Box 162\6\  img232
Date  28th September 1933
  
Lodge Plugs Limited,
Rugby.

Telephone. 276 RUGBY (2 lines)
Established 1904.
Telegrams."LODGE, RUGBY"

Messrs. Rolls-Royce Ltd.,
D E R B Y.

Your Ref.
Our Ref. BH/EW.
Date 28 September 1933.

DIRECTORS.
J.{Mr Johnson W.M.} ALFRED HOPPS.
BERNARD HOPPS.
ALEC. M.{Mr Moon / Mr Moore} LODGE.
F.{Mr Friese} BRODIE LODGE.

All letters must be addressed to the Company, not to individuals.

For the attention of Mr. Robotham.

Dear Sirs,

We are returning herewith the Model X335. plug which the writer brought away with him on his recent visit.

We have tested this plug on a standard aero magneto at 100 lbs. pressure with the plug gap set to 20/1,000", under which conditions the plug sparks perfectly. The plug centre was then removed and flashed at 15,000 volts. The electrodes of the plug were then cleaned, without however cleaning the mica insulation, and the plug was again reassembled, the gaps adjusted to 20/1,000", and again tested at 100 lbs. per sq. inch, at which it sparked satisfactorily.

We cannot understand the failure experienced by you with this plug, and we can only conclude that a piece of carbon may have temporarily lodged across the gap causing a short circuit, and the carbon may have become dislodged when the plug was taken out for examination.

We suggest that you again test this plug and let us know if you still find it defective.

Yours faithfully,
LODGE PLUGS LIMITED,
Bernard Hopps.
DIRECTOR

Enclo: (Plug)

ENCLOSURE Nº 929
"JUSTSO"
  
  


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