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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).
Investigating the suitability of low tension conductors for the 40/50 HP chassis electrical system.

Identifier  WestWitteringFiles\C\August1919\  Scan20
Date  25th August 1919
  
To EFC. from E.{Mr Elliott - Chief Engineer}
Copy to C.J.
" " BN.{W.O. Bentley / Mr Barrington}
" " EH.
" " DA.{Bernard Day - Chassis Design}
" " BY.{R.W. Bailey - Chief Engineer} X.2448

ORIGINAL.
25 AUG 1919
RECEIVED

E1/G22/8/19. 2

RE LOW TENSION CONDUCTORS FOR 40/50 HP.CHASSIS.

You will recollect that we have asked you to investigate whether conductors of .175" outside diameter for the unarmoured cables on the electrical system of the 40/50 H.P. chassis will be possible and suitable.

The low tension conductor hitherto used by us has 70 strands of No. 36 S.W.G. wire, and this will carry a current of 3 amperes at a density of 1000 amperes per square inch. Mr. Royce has been using some of this for the house lighting installation, carrying currents of 15 amperes charging the battery. This means that it is working at a density of about 5000 amperes per square inch.

In the light of this, Mr. Royce would like you to tell us if this 70 strand 36 gauge cable will do for our wiring system on the 40/50 H.P. chassis, with the exception of course, of the heavy current leads to the motor. You would require such a cable with .175" diameter outside of the insulation for unarmoured cables and .150" for armoured cables. Most of the conductors are only carrying currents of low quantities.

The lead from the battery to the distribution board, and the leads to the ammeter will carry the largest current, say, 15 amperes, and if you find the voltage drop on these connections is too great for the size of cable we have mentioned, then it will be necessary to use a heavier cable, but only for these three conductors.

(Contd.)
  
  


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