Villiers battery charging system ?

[R]

I enjoy playing with my Villiers stuff but I have no illusions     

Aye ! 
As soon as the march of history is trotted out, I compare my lil Villiers 125cc at 3 bhp with the last of the KTM 125cc GP bikes.
At 55 BHP, thats 440 BHP/Litre    Now thats a full Grand Prix race spec engine, but still ......

Thanks for your comments. I do have the Villiers book, but not read through it lately. Or even found it recently !.
I don't remember it giving a really detailed account of the electrics, just the bare basics. ?
I'd be curious what form that long resistance wire took in the later 1950s models, if it had to deal with a full 30w output.
That'd be a bit of heat to shed .....

[33d6]

I’ve hunted out the magnet details for you R. Magnets on the 18 watt job are 1&1/8”wide and the 24watt magnets are 1&7/16”. The difference is in their width.
One has to be careful with Villiers magnetoes. There can be subtle differences that are never mentioned anywhere. For example the overall flywheel width of the near identical post war 10D and 6E engines are different, the 10D is 1&7/8” and the 6E 2&1/16”. I’ve never bothered to measure the actual magnets. This is never mentioned anywhere in any Villiers manual I’ve seen. I suspect it never occurred to Villiers that it would ever become relevant.

[R]

Interesting. Does this mean you can't just swap flywheels between different models of engines,
or that you can't even swap the whole kit & caboodle between engines ?

I merely pondered swapping from a 2 coil set to a 6 coil set, without any serious intent...

[33d6]

I can only answer that with the classic response “It depends”. Villiers made made flywheel magneto’s for some 50 odd years and made them by the million. No one knows all the subtleties that arose over the years. Just remember Villiers made these units as matching pairs and numbered them accordingly. It’s easy to check whether they are factory originals. After that you’re on your own.