The Marston Sunbeam Club & Register Forum

Hello.
I am just wiring up a 1935 Model 8 and am planning on using a 6volt DVR2 in place of the regulator.

I have used these on a number of old bikes in the past and been very satisfied.  My problem is that I have a spare 6volt positive earth DVR2 here and available to use.  If I fully insulate it will it be ok to use on a negative earth system? 
http://dynamoregulators.com/

The Company are on annual leave this week so I cant ask them, but do any of you electrical whiz kids know please?.

Thanks, John.

Why not flash the field coil to reverse the polarity of the dynamo?
http://dynamoregulators.com/faq.php
Read this on flashing the field..John

I would like to keep it as original as possible, and it was originally negative earth.

Thanks.

Im with SM John on this one. I converted my Lion to positive earth when I fitted the dvr to it, simply because it then falls into line with all the others and save confusion. If youve already got the regulator then it would make sense to use it.
Im pretty sure that the dvr2 doesnt earth through its casing anyway so theres more to bodging it than just  insulating it.

Steve

Thanks for all the replies Guy's.

It was always my intention to get the negative earth DVR2 once the firm reopened.  As I'm always a bit impatient, it was really a question of the wisdom in using the one I have for testing purposes if fully insulated.

In conclusion I think its probably safest to just wait until I have the right one.

Thanks again,  John.

I'd guess the answer is that none of us are sure whether you can get away with connecting it up that way but I suspect not. I don't know the box you're using but if it's like the Wassells ones I use, they don't earth via the body but have a 'live' and 'earth' wire, but still come pos and neg earth so it's presumably not possible simply to reverse the wires - presumably if you did the polarity of the Field wire would be adrift.
But I agree with John and Greybeard; the thing is flashing the field is only temporary - you aren't making any permanent changes to the system and once you have made your tests you can just flash it back to neg earth again.
All you need to do is connect the battery up positive earth and take a live lead (from the negative, obviously) and touch it against the F terminal on the dynamo a couple of times so that you get a few sparks, that will polarise it positive earth and you can make your tests. Having done so,  when the Neg earth box arrives simply swap the battery back to neg earth,  flash the positive lead on the F terminal and you will be back to standard again and can connect up the neg earth box.
All you are doing is setting the polarity of the small amount of magnetism that remains in the laminated steel core of the dynamo body field coil; it's always worth flashing it anyway because this magnetism - which is a basically the same as you get in a nail if you use it as a magnet keeper - can either die away or even reverse when left in storage.
I'd guess loads of people have paid for a dynamo rebuild simply because the residual has faded away through lack of use.
On a similar tack probably the best thing I ever learned about dynamos was if you get no charge with the engine running, take a flying wire from the battery live and poke it into the field terminal with everything left connected. This will often fire it up.
The residual magnetism is effectively the spark that gets the charging going so if it has dwindled or is the wrong polarity you won't get a charge at all - but it's a really simple thing to fix that doesn't involve any electrickery!   
Go for it...well assuming you haven't got the negative box already!
Cheers Rick

Thanks Rick,

I have the negative earth unit now, but it looks like I could not have used the positive earth DVR2 even if insulated.
This is the reply to my question from the manufacturer. (dvr@dynamoregulators.com)
"Dear John,

You could not speak to us last week as we were closed for a week holiday.
The Positive earth regulator must be fitted to a Positive earth dynamo, with battery Negative as live. Insulation is not possible. Easy enough to re-polarise dynamo.
Kind regards,
Mike Hutchings

So there we have it...  Thanks everybody for their interest.
Regards, John