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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).
Proposal for electrical circuits, fuse arrangements, and a switchbox ignition test system.

Identifier  ExFiles\Box 65\2\  scan0002
Date  8th September 1928
  
To EFC. HS.{Lord Ernest Hives - Chair} (FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} (AND E.{Mr Elliott - Chief Engineer}
X7730
RL/M.8.9.28.
c. BJ. Wor.{Arthur Wormald - General Works Manager}
EAC.10 ELECTRICAL CIRCUITS. X.7780. X.7560.

The battery has no fuse for the motor and main switch circuit. If one was provided there would be danger of this going, and high voltage given by dynamo (except for its field fuse). It however has a 45 amp. fuse (special 3/30s) to protect ammeter and switchbox: this must be a very safe fuse.
After the switchbox, and in parallel to it, the circuits are grouped, and each group has a separate fuse - standard fuse 15 amperes.
One difficulty arises in that the teazer circuit (starter press button) comes from one of these fuses, and is more than 15 amps. Therefore starter battery fuse should be made more important, and protect the teazer circuit in parallel with switchbox.
Gadget circuit - No.6 fuse - klaxon, body lighting, and all other coachbuilding accessories via auxiliary distributing box.
No.5 fuse - side and tail.
" 4. " - head
" 3. " - ignition. } 7 fuses in all.
" 2. " - dynamo.
" 1 " - (field) dynamo

SWITCHBOX & IGNITION TEST

We propose to arrange this:
This does all you want for running except that you cannot shunt slow running on battery ignition only.

To test we have electrical interlocked press button (turn as switch) to cut out magneto on 1 and 2 positions, but the special point is the interlock to prevent the magneto being cut out in 3 position. To do this we have contact at the back arranged -

[Diagram of switch positions with handwritten labels: 3) M & C., 2) M.{Mr Moon / Mr Moore} B. & C., 1) M.{Mr Moon / Mr Moore} & B., 0) OFF.]

P.B. on for two positions.
[Diagram of a lever mechanism labeled P.B, E, B]
Off position.
Then in No.3. on magneto earth possible.

This means no alteration to internal switch mechanism, only to the magneto contact at back.
This system can be used on present Phantom if desired but I prefer to make one change at EAC.10.

R.{Sir Henry Royce}
  
  


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