Electrical system  (iss 135)

Wiring diagrams:

For military Nortons, a number of  6V negative (-) earth systems have been used based on the existing equipment or the operational requirements of the time at which they were applied. It was a relative simple system and used by most of the contemporary British motorcycle manufacturers. Some used Miller equipment.
Lucas supplied both the ignition and lighting system components in the form of the Magdyno, a combination of a magneto to feed the spark plug and Dynamo to deliver power to the (many times troublesome) lighting system. On all military Nortons, the lighting switch and Ammeter (if applied) were mounted into a small panel which in turn was screwed onto the top backside of the Lucas DU142/DU42 headlamp shell. On civilian motorcycles, owners had an option to mount the electrical equipment into a panel mounted on top of the petrol tank. These motorcycles were then provided with a completely closed headlamp shell type Lucas D142.

"Lucas invented darkness" or Lucas "Prince of darkness" are some of the many adjectives for the products of Lucas manufacture. Many of the problems were caused by bad maintenance or by the harsh environment into which the bikes were operated.

There have been 2 basic electrical equipment systems where the later version was used in four different electrical wiring schemes.

Electrical equipment variation one:
The first machines of 1936 did not have the luxury of the later introduced CVC (Compensated Voltage Control), but had to do with a switch to have the dynamo disconnected, at half charge or at full charge. A wire coil resistor mounted to the headlamp switch panel was used to "burn-off" the excess of power when the system worked at "half charge". This system is also described as the "three brush dynamo"  system.
The system worked using a switch with "OFF", "C", "H" and "L" positions. When the battery was full, the rider could set the system to "OFF", in which case the dynamo was disconnected from the system. When the battery became discharged, the rider had 2 choices, half charge "C" for riding without the lights or lights on and full charge, switch position "H". The dynamo for this system was provided with an electro-magnetic cut-out which connected the dynamo to the charging circuit as soon as the dynamo voltage rises above that of the battery and disconnected the dynamo from the charging circuit when the dynamo voltage dropped below the battery voltage, to prevent the battery discharging itself through the dynamo.
Only the 1936 WD machines used this system as the CVC was introduced in 1937 which led to the "Norton 1937 specification" annotation which was the standard for all machines after that.

Electrical equipment variation two:
The CVC (Compensated Voltage Control) took the worry of proper charging from the rider and is basically a electro-mechanical regulator. It regulates both Voltage and Current by two coils working as electromagnets activating electrical contacts when either Voltage or Current exceeds a certain maximum value. The dynamo did not have the cut-out as mounted on the previous machines. The regulator (CVC) was factory mounted on the right hand upper rear chain stay above the tool box. In military use, these boxes sometimes changed position to the opposite left hand side upper rear chain stay. Ease of access to the wiring was probably the driver for this "field modification". 
Regulators working on the same principles were used throughout the motoring industry of that time until replaced by the electronic versions of today.
 

The wiring diagram changed over time based on operational requirements.
Initially the basic civilian scheme was applied using a 3 position headlamp switch (U 39). "OFF", "L" (pilot bulb and rear light) and "H" (main bulb and rear light) and an additional High/Low beam "Dip/Dipper/Dimmer" switch mounted on the left hand side of the handlebar. Civilian bikes had a brake light option as well as a sidecar option. Military machines never had a brake light based on available diagrams.
Late 1939 (between October 21st, based on latest known original machine and December) a requirement for a tail light only option was added requiring some adaptations of the earlier machines. For this option a 4 position switch, "OFF", "T", "L", "H" was introduced.

On May 5th 1941, DME Circular B.141 mandated the removal of the Dipper switch from the existing motorcycles and the fitting of new headlamp masks (black-out).
Pictorial evidence showed that this ruling was not always followed. Most likely it was only done during major overhaul or rebuilding of the bikes.
With the introduction of the black-out mask, there was little use of the dipper switch arrangement with High/Low beam option.  The bulbs were now double filament, giving a spare filament in the same bulb.

Nearing the end of the war, an "improved" wiring scheme was introduced, to reduce the number of wires running from the front fork to the rest of the machine after it was recognised that many electrical faults developed through chafing, resulting from the continues movement of the front fork. This system was also introduced on other brand motorcycles like the BSA M20.
A late wartime Norton maintenance and instructional manual describes a modified electrical system. This system consisted of the deletion of the ammeter, and introduction of a push button in the instrument panel to change from Pilot to Main bulb and a "new" switch (U39-L15) mounted at the right hand side under the saddle. With this configuration there was only one lead left from the frame to the headlamp.
The instrument panel on top of the headlamp shell was made without aperture for the 4 pos switch and ammeter, and only a smaller hole to fix the push button.
The switch had also 4 positions : "Test", "Off", "T" (tail only) and "H" (tail and headlamp on). The test position connected the D terminal of the dynamo directly to the tail light. The brilliance of the taillight was then supposed to be a measure for the operation of the charging system, see attached snippet from the M&I manual. 
  Click to enlarge

Lamps were 24W main bulb (double filament), 3W pilot bulb and 3W tail lamp bulb. The16H and Big 4 the sidelamp and Big 4 axle flood light were also 3W bulbs.
An "Altette" horn complemented the system where the early bikes used the HF935 and the later used the HF1235, operated through a horn push button on the right hand side of the handlebars.

Wiring diagrams for 16H and Big4 are basically identical apart from the sidecar light on the pre 1941 Big 4 sidecar combinations and the additional axle flood light and change over switch on the later Big 4 sidecar combinations.

Note:
It appears that the military machines did not always follow the Lucas given colour codes for all periods. Up to October 1939 the dipper switch wire was a combination of red, blue and black wires in one sheath whereas the Lucas drawings all give 1 blue & white and 2 blue wires in one sheath.
The wire from the switch to "A" of the CVC regulator is coded red & yellow on early machines and purple & white on the later machines.
The wire from the switch to the tail light is coded red/black on the earlier machines but coded  red on later machines.
Colour codes for the simplified scheme are again slightly different from the earlier schemes, F CVC to Dynamo became green instead of previous green black and single wire to headlamp was now only blue.

16H
pre 1937

16H
1937 to 1941

16H
1941 to 1944/45?

Big 4
1941 to 1943

1944/45 upwards

Wires:

On  unrestored remains of a machine from Contract C5109 (1939/1940) the following was observed:
The wires were tin plated copper wires covered with rubber insulation. Identification was through coloured rubber sleeves near the terminals. The dipper switch wire was like a present day 3 lead wire with blue coloured individual insulated leads combined in one outer cover.
Note:   These early rubber covered wires used tinned copper leads because the sulphur in the vulcanised rubber leads to oxidation of the copper.
             Rubber itself deteriorates through the exposure to oxygen and UV radiation, becoming very hard and brittle. For this reason not many original looms still exist.

Remains of original wires found on a  switch as applied in the late war electrical system (1944/45) appeared to be rubber like, similar as described above.
This indicates that rubber encapsulation was used during the entire war.

Picture from article of Steve Madden, courtesy Henk Joore's  WDBSA.nl website.

At least 2 different diameter wires have been found, approximately Ø 4,6 mm and Ø 5,7 mm as measured on the insulation.

Wiring remains on a late-war (re?)built machine showed to have cloth covered leads. It was not possible to assure this was factory applied. Whether the use of the cloth encapsulated wire was widespread is difficult to say. Cloth encapsulated wiring was used on motorcars and motorcycles in the 20ties and 30ties.

Wiring harness and wire fixing
The main wire loom was protected by a rubber sleeve from the headlamp shell mounted switch panel through a loop clamp on the right hand side of the front fork, under the upper frame tube until the saddle tube frame casting. From there on the individual leads went to the Dynamo, CVC, and tail light. The life horn wire ran parallel to the wire loom/rubber sleeve from instrument panel directly to the horn. The horn earth wire ran directly from the horn to the handlebar push button. The battery earth wire was fixed to the top battery carrier stud.
Attached pdf "Wiring harness cable clamps" shows the clamps and positions as best as I have  been able to reconstruct. I do not claim to have it absolutely correct but it is better than ever seen before, which is nothing!

Batteries and CVC (Constant Voltage Control, MCR1) regulators
It is not exactly known which battery type was used on the 1936 built machines.
From 1937 onwards, the military machines were provided with a fairly lumpy "Ni+Fe" (Nickel-Cadmium) alkaline battery.
These "Ni+Fe" batteries were purchased under the Lucas name "C105 Ni-Fe battery" but in actual fact produced by the "Batteries Ltd. Redditch" company.
A more elaborate description of the Lucas C105  batteries can be found via link below:
                          pdf article on Ni+Fe batteries . 
First mention of the "Ni+Fe" type was in the 1937 Norton production administration and the last use of it was registered in October 1939.
The "Ni+Fe" alkaline batteries were replaced in late 1939 by the more "normal" Lead Acid type batteries, primarily the Lucas PUW-5E and equivalents later in the war. The India Office used the Exide lead acid batteries for all their machines.

Because of the different charging requirements there were also two types of MCR1 CVC regulators. It is believed that prior to the introduction of the lead acid batteries by the military, civilian regulators did not have a battery type marking and that Ni-Fe type regulators were marked "NI-FE" on the front bottom of the regulator above the F A D E markings.

With the introduction of the lead acid battery by the military (late 1939) the lead acid battery regulators were marked with "LEAD-ACID", likely to assure the application of the correct regulator.
Pictorial evidence suggest the Ni-Fe batteries were basically out of service by mid 1940 but the "LEAD-ACID" marking appears to have lasted until mid 1942.

Lead Acid batteries could work with Ni-Fe CVC's but it was only allowed for a short period and not recommended.

Dynamo's E3.HM
Dynamo's used on the Norton were Lucas part number 200286. These turn anti-clock when looking from the drive side. Lucas part number 200285 was used on e.g. BSA M20. The only physical difference between these dynamo's is the commutator end bracket and brush holder. A 200285 housing with field coil can be used for a Norton when the correct commutator end bracket and brush holder is fitted to it. A BSA dynamo can be used on a Norton without changes but in that case the carbon brushes and the collector will wear much more quickly due to excessive sparking.

 Dynamo 200286 on left (Norton), 200285 at right, showing the different dynamo commutator end brackets (different production years hence not equal in all aspects)

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Commutator end brackets, pn 200215 at left (Norton) and 200216 at right (other brands).  

Actual equipment:

The Electrical equipment picture page gives some indication on what the different parts basically look like.

Many (but not all) Lucas parts are provided with the manufacturing date stamped into them. If you really want to restore a bike to "factory" fresh condition, searching for correctly dated Lucas equipment should make your life exciting.