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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).
Bench test report on a modified Spectre switchbox to assess current carrying capacity and volt drop.

Identifier  ExFiles\Box 166\3\  img039
Date  2nd May 1935
  
Hs{Lord Ernest Hives - Chair}/Wst.1/MA.2.5.35.

TESTS OF MODIFIED SPECTRECodename for Phantom III SWITCHBOX TO R.R.SCH.781.

Bench tests have been carried out on the SpectreCodename for Phantom III switchbox to R.R.Sch.781 to test the current carrying capacity of the main contacts and the volt drop across them.

A current of 50 amperes was taken, as being the maximum likely to be passed through the main contacts, under extreme conditions.

A current of 50 amperes, was therefore, passed between the battery positive and starter supply terminals, and maintained for 1 minute. At the end of that time, the volt drop between the terminals was .13 volt, and the contacts were only just warm.

In order to test the main contacts carrying the current for the lamp, ignition, accessories, etc., a current of 20 amperes was passed between terminals dynamo positive and H, for a period of 30 minutes. The volts dropped across these contacts were :-

Dynamo positive contact .035 volt.
H Lamp contact .075 volt.

Both contacts only became warm.

We consider therefore that this switch is quite satisfactory electrically.

Hs{Lord Ernest Hives - Chair}/Wst.
  
  


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