Lynx I MkIII purchase

[Alastair Thomas]

My brothers took the Lynx to Normandy last year and had a lot of fun. Right at the end of the week the battery went flat and following a lot of help from fellow enthusiasts, the dynamo was declared u/s.
I took it to my local auto electricians and they tell me that the armature is u/s and needs a rewind. £300 was quoted.
In trying to avoid this expense I dug out all our spare dynamos. One is clearly marked 6v (the Lynx runs on 12 v).
Another has no markings at all and the third looks as though it is a three brush device. It is marked FordQ-5.
My question is can anybody tell me how to tell the difference between a 6v device and a 12v one?
Having accidentally reverse polarised my dynamo on my 1948 Riley once, I wondered why the red light would not go out. I measured the voltage at the output of the dynamo and it was 60v in the wrong direction. Problem solved. However this prompts me to ask what is the difference between 6v and 12v dynamos? The only suggestion I can come up with is that the armature of the 6v one presumably has thicker windings as it is required to supply twice the current (at least in theory).
Does this mean that I can:
a) use a 6v dynamo in a 12v set up, or
b) use the armature from a 6v dynamo in a 12v dynamo?
Kind regards,
Alastair
p.s. what is the tin can seen in the photo below?

[charlie fitton]

The tin can is a voltage cut-out relay.

(Hopefully your helpers checked that)

The 6/12V armature is an interesting question. My gut leans towards yes, But experts actually know.


f

[Andrew Rowe]

I have done many a conversion of generators from 6v to 12 volt. We use the original body and armature of the 6 volt and get a 12volt gen, something like a Lucas C45, 12volt ( The 45 means 4.5" in dia. ) so find one that is roughly the same diameter as your original that you want to keep. Take the field coils from this gen and put them into the 6volt, and you should be able to achieve 12volts. You can normally find these old 12 v Lucas gens. for $5
Find a gen. that matches your dia. , screw pattern for fixing the fields, normally just two field coils, and put them in the correct way. You can test your new rebuild by "motoring up" , but also test on a testbed to make sure you achieving the desired output , Cheers Andrew.

[Alastair Thomas]

Dear Andrew and Charlie.
I was distracted by other projects so have only just seen your helpful replies.
Thank you
Alastair

[Alastair Thomas]

I robbed a 6v dynamo of its armature, tidied up its commutator and rebuilt the dynamo.
I was on my own so could not lift the engine cover by myself but instead used three chain hoists.
The dynamo is now fitted and will be tested in the next day or so.
A couple of points to note:
1. I measured the resistance from the field connection to earth on both the 6v and 12v dynamos and they came out at approximately 4.5 Ohms and 9 Ohms respectively.
2. I am very familiar with the Lucas C45 P dynamo having owned a number of 1940s and 1950 British cars running on 12v. However, I noted during this exercise that one of my 6v (clearly marked as such) dynamos was a Lucas C45P. It must be said that this is the first time I have come across such a beast. It came with a Ford V8 Flat Head engine I bought and, according to my Lucas spares book must have been fitted to one of the early Allard cars.

[Dave Newcomb]

The International Early V8 Ford club has been around 50 yrs, The best web site is Fordbarn.com. Full of experienced fellows. Dave

[Alastair Thomas]

Thanks Dave.
Alastair