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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 H.D. Symons & Co. Ltd. providing particulars of Standard E.R.A. Electrodes.

Identifier  ExFiles\Box 61\1\  scan0166
Date  23th March 1931
  
Telephone: KINGSTON 1708.
Telegrams: INSULATION (PHONE) KINGSTON-ON-THAMES.
Park Works, Kingston Hill, Surrey.
H.D. Symons & Co. Ltd.
ELECTRICAL INSULATION SPECIALISTS.

Your Reference EFC3/AD.
Our Reference HDS/AMP.
23rd March, 1931.

Messrs. Rolls Royce Ltd.,
Nightingale Road,
DERBY.

[STAMP: RECEIVED 24 MAR 1931]
[STAMP: E.F.C]

Dear Sirs,

Replying to your letter of the 19th instant in which you request us to send you particulars of the Standard E.R.A.Electrodes, we would say that these are as follows:-

"The bottom electrode shall consist of a
'flat disc of brass 3 in. diameter by ¼ in.
'thick.

"The top electrode shall consist of a
'solid cylinder of brass 1½ in. diameter
'by 1½in. high.

"The sharp edges shall be removed from
'the electrodes, but the radius at the
'edge must not exceed 1/32 in. "

For your convenience we would add that the above information is contained in the British Electrical & Allied Industries Research Association Tehcnical Publication Ref. A/S2, "Directions for determining electric strength of fibrous insulating materials", Page 5, Paragraph 11.

These electrodes have been adopted as

[Left Margin Text]
Varnished Cloth.
Varnished Paper.
Varnished Silk.
Flexible Varnished Tubing.
DUPLY TUPLEX Slot Insulation.
EMLIN TAPE.
FLEXIBLE MICA SILK. MICA PAPER.
SYMOID CLOTH.
  
  


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