B.T.H Magneto-Generator Series 'A' Comet

[Simon Dinsdale]

Has anyone used a Wassell regulator with a Miller magdyno to replace the cut-out and 3rd brush? Is it any good? Is there a wiring diagram for it?

The dynamo part of a Miller mag dyno should be able to be converted to use an electronic regulator suitable for dynamo use as the Miller unit is a standard field winding. You will have to remove the cut out and convert it to 2 brush operation which is doable.

I don't know anything about the Wassell regulator or even if its suitable for a dynamo use as I have never used one. I used to make my own electronic dynamo regulator for my own use but stopped making them and now use the DVR2 regulator on several bikes and have had no problems in over 12 years and thousands of miles of DVR2 use and I am just a happy customer and have no connection to the manufacturer. One advantage about the DVR2 is the unit can be used for 6V or 12V operation so if you are 6V now it will work and if you later upgrade to 12V you don't need to replace the regulator, you just connect to the unit using different wires coming out of it:

Dynamo Regulators product range - Dynamo Regulators Ltd

Dynamo Regulators Ltd - Electronic Voltage Regulators for classic motorcycle dynamos. Our DVR2 is the modern replacement for old bobbin type units.

dynamoregulators.com

 

[Marvel]

The DVR2 looks the same as the Wassell albeit a bit more expensive. My question was more how to convert the 3 brush dynamo to 2 brush to allow it to be connected to the Wassell or DVR2. The wiring diagrams for both seem to refer to the 2 bush arrangement.

 

[Chris. S]

Hi Delboy. Fortunately I don't have time to get into circuit design at the moment. If you Google; transistor series regulator circuit diagram; you will get plenty to choose from. Personally, if I were going to experiment with the BTH permanent magnet dynamo, I would buy a DC buck/ boost converter; as mentioned by Vic. I may give it a go, after I've finished my Ariel square four project. Don't hold your breath.
Cheers, Chris.

 

[bmetcalf]

This may be useful: https://www.dynamoregulators.com/documents/DVR3 3 brush.pdf

Also, this: https://www.fordgarage.com/pages/generator.htm

 

[A Nut]

All of my dynamo equipped bikes have been converted to electronic regulators some 12 v (Series C Shadow and Comet) whilst the A Comet is still 6v. I use AO Services V Reg 2 which like the one that Simon uses can be converted to 12v at a later stage. They are quite small and will fit inside the Miller case for a post war bike but for the Series A I have fitted it inside the toolbox. I have to admit that if I go out at night I very often take my '59 Triumph Thunderbird as I have just fitted a new alternator along with an electronic regulator and the biggest 12v AGM battery that I can get into the case along with a H4 halogen bulb I can see where I am going (and at speed!)
Brian

 

[Marvel]

So I persevered with the 3 brush regulator and made a new insulating plate out of a sheet of Paxolin to replace the broken one. I made a new set of brushes out of some similar Lucas ones. Remade the connections to the cut-out, adjusted the points gap to 0.031”, checked it closes at 6+V and cleaned-up the commutator. Hey presto it charges 2A on half charge at about 40mph and doesn’t exceed this so the 3rd brush is doing it’s job. All set now for the Wyle Valley Early Bird run tomorrow.

 

[Georgehrd]

Hello Simon,
Do you have better pictures of your BTH cutout withe the BTH circle on the top.
Thank you.
Michel.

Hi vin998 do u know where I could source a cable for that mag generator thanks

 

[Simon Dinsdale]

Hi vin998 do u know where I could source a cable for that mag generator thanks

My series A originally belonged to my late Dad who had the BTH magdyno rebuilt 15 years ago and when it came back there was a new cable fitted by the rebuilder. I think he used FTW Motorcycles in Sheffield but not 100% sure. They don't appear to have a website and I don't even know if they still exist as a company and this is the only contact details I can find for FTW:

FTW Magneto and Dynamo Rebuilds Sheffield S6 2AD, Motorcycle Repairs

FTW Magneto and Dynamo Rebuilds in Sheffield S6 2AD - Company Profile, Phone Number, Address, Postcode, Map and more

www.misterwhat.co.uk

Simon (vin998)

 

[Chris Launders]

FTW closed several years ago, the owner died suddenly.

 

[Georgehrd]

Thanks very much for the replys and help guys I tried to contact but no luck