Misc: Charging Systems Series 'C' Rapide: 6v or 12v?

[Cannop]

I've just bought my first Rapide, a 1950 series C example which requires recommissioning. The bike isn't with me yet but I inspected it on Wednesday and the only missing parts I could see were the battery and the battery clamp bolt and nut.

I'm now wondering if there is a way to tell if it's still 6v or has been converted to 12v just by inspecting some photographs? Below are a couple of the charger/dynamo area, if anyone can tell me if it is actually possible to distinguish 6 or 12v from these I'd be happy to know how!

 

[timetraveller]

Look at any bulbs fitted. They will be either 6 or12 volt, Alternatively, and if you are confident in using a volt meter, check various things on the bike when you have it.

 

[b'knighted]

Another clue would be to remove the cover from the little box on top of the dynamo. If it contains a cylindrical coil wired up to the bike it may be the original Miller cartridge indicating six volt. If it is a more modern electronic device it is likely, but not necessarily, twelve volts.

I believe that the bikes left the factory with a positive earth six volt system. Most 12v systems are negative earth.

If you have access to a 6v power supply like a battery charger or a low voltage battery see if it will light the bulbs brightly enough to show that they don’t need 12v.

 

[chankly bore]

If your horn is an original-even though the bezel and acorn nuts may be reproduction, the original type plate on the terminals will indicate 6V or 12V. You can put 12 volts through a 6 volt horn, briefly, but it is not wise to. Lovely to see original , correct, cheese- head screws, by the way. Good luck with it.

 

[bmetcalf]

Regarding the screws, grind the tip of a screwdriver to fit them well and don’t use it for anything else. Same for the nine screws on the clutch.

 

[Cannop]

Thanks for the replies, much appreciated. I did take a couple of screwdrivers with me to check out the bulbs but didn’t feel comfortable undoing anything as it was an auction sale! It was apparently bought by the previous owner in 2016 as a “barn find” and was then comprehensively rebuilt (and subsequently rarely used), so I’m thinking it was probably converted to 12v when that work was done, I guess I’ll just have to be patient and wait for it to arrive.

 

[Graham Smith]

If you take the regulator cover off…

And you find a modern electronic regulator inside that looks like this…

If the green looped wire is intact, it's 6v.
if the green looped wire is cut (and sealed), it's 12v.

If it's the AO regulator that you have, you can download a data sheet from here on our forum website…

https://www.vincentownersclub.co.uk/resources/v-reg-2b-dynamo-voltage-regulator.4407/

 

[TouringGodet]

I believe that the bikes left the factory with a positive earth six volt system.

I believe factory standard was 6 volt negative earth. The two metal tabs shown together mount to the frame, and the end labeled as negative battery is therefore a direct connection to the frame.