Advice on regulating a 6V motorcycle alternator.

[Nick E]

I hope it is acceptable to ask for advice here. I am based in the UK and currently restoring a British 1964 Velocette LE motorcycle. It is fitted with electrical components made by the, now defunct, Miller Company (also British).

The vehicle has a 6V 3 coil alternator with permanent magnets mounted on the flywheel. It is a former police bike and has an uprated alternator which does not convert well to 12V but is rated at something over 60W.

Originally the bike just had a lead acid battery, a selenium rectifier and no regulator but the load was balanced by a very complicated 8 pole switch which switched in the appropriate number of coils depending on the electrical load required. This worked reasonably well with an open vented lead acid battery.

I wish to fit a Cyclon 6V 8Ah sealed battery and understand that this will mean I must fit a regulator. My problem is that nobody seems to make a 6V regulator for an alternator. Podtronics in Texas make a 12V unit which will also allow conversion of the Lucas 6V alternator to 12V but, as mentioned, this is not advisable with my alternator. They also make 6V dynamo regulators.

I have spent considerable time searching for a suitable device but have come to the conclusion I will have to build one. I have the necessary amateur skill to do so but really have no idea about the design i.e. circuit design and component values. I realize heat dissipation is important but the mechanics of that I can deal with.

Any advice would be very gratefully received having spent interminable hours searching for a solution.

 

[Bob S]

Here is a very simple and inexpensive 6 volt to 12 volt DC-DC converter rated at about 10 watts:
http://www.aaroncake.net/Circuits/6-12conv.asp
Adding or replacing about 4 components could raise the output rating to 60 watts.

 

[berkeman]

Here is a very simple and inexpensive 6 volt to 12 volt DC-DC converter rated at about 10 watts:
http://www.aaroncake.net/Circuits/6-12conv.asp
Adding or replacing about 4 components could raise the output rating to 60 watts.

I'm not sure, but I think the OP wants to stay with the 6V battery and electicals on the bike. Otherwise, he could just convert over to a 12V system and use standard components.

 

[Nick E]

That is correct I do wish to stay with the 6V system.

The owners club for this particular motorcycle has just lost the services of one of the members who had an in depth knowledge of this particular motorcycle's various electrical incarnations and regularly wrote articles for the club newsletter. I was in correspondence with him shortly before he died and he sent me graphs showing the outputs of the various alternators fitted to these bikes. He pointed out the appalling output of the higher power 6V police machine alternators if converted to 12V, the standard Miller and the Lucas 6V alternators converted satisfactorily.

He did not go into detail about why this was so but was emphatic in not converting my alternator to 12V, hence my problem.

 

[vk6kro]

Volkswagon beetles of about that era (up to 1965 anyway) used 6 volt systems and 6 volt regulators. They used DC generators with brushes and commutators.

If you had a look around, like at this place:
http://www.bus-boys.com/charging71.html#CHARGING
you might be able to pick up an old regulator.

These would be electromechanical (3 relays, I think) and you may need expert help (auto electrician) to get one working on your motorbike alternator.

 

[Nick E]

I did see that VW fitted a 6V regulator bt was unsure whether it was for a dynamo or alternator powered vehicle.

The good news is that I have this eveniong been told of a source of solid state 6V regulator. I will know for sure tomorrow. In the meantime I thank you all for your comments and advice. I will report back with progress in case anybody is interested!

 

[Danger]

This would be a great time for Wolram to weigh in if he's available. (He's had a bit of difficulty with communication for the last while.) He's a collector of, and an expert in, English motorcycles. He's built some beautiful machines.

 

[berkeman]

This would be a great time for Wolram to weigh in if he's available. (He's had a bit of difficulty with communication for the last while.) He's a collector of, and an expert in, English motorcycles. He's built some beautiful machines.

Can you please PM him this link, Danger? I agree.

 

[Danger]

I can't PM him, Berkeman, because my mailbox is full. For some reason, that negates transmission as well as reception. I will, however, attempt to e-mail him with a copy to Kia in case he can't receive his own mail.

edit: I just realized that I don't know how to use the PF e-mail forwarding function, and I can't remember either of their real e-mail addresses. I did, however, leave him a message on his 'friends' board.

 

[Bob S]

The good news is that I have this eveniong been told of a source of solid state 6V regulator. I will know for sure tomorrow. In the meantime I thank you all for your comments and advice. I will report back with progress in case anybody is interested!

If you plan to use the charger to charge a 6-volt sealed lead acid battery while running the motorcycle accessories, the charging voltage needs to be maintained between about 2.25 to 2.3 volts per cell, so a straight 6 volt charger won't work. Here are articles on lead acid battery voltages for charging:
http://batteryuniversity.com/partone-13.htm
and another:
http://www.powerstream.com/SLA.htm
There are bucking (voltage reducing) switchmode power supply designs that can be bootstrapped; meaning that if the alternator output voltage is less than the regulating voltage, the circuit can be bootstrapped so that the output voltage equals the input voltage. This would allow powering all the motorcycle accessories even if the alternator voltage dropped below about 6.75 volts.

 

[wolram]

Re building an LE velo, the owners club have all the info

http://www.velocetteowners.com/

If they don't know then i am lost.

 

[Danger]

Thanks, Woolie. Nice to see you back in the circuit.

 

[wolram]

Thanks, Woolie. Nice to see you back in the circuit.

Thanks Danger, i found the site i wanted,
http://www.leveloclub.org.uk/index2.htm
This club is dedicated to the LE or noddy bike as we used to call them

 

[Danger]

This club is dedicated to the LE or noddy bike as we used to call them

Oh, man... when I see the word 'noddy', all that comes to mind is Slade, one of my absolute favourite bands.

 

[Nick E]

Today I collected a purpose made module from a supplier of parts for old motorbikes. In conversation he told me that he sells around 6 per year because most people convert to 12V. The unit appears well made but is of sealed construction. The whole thing is within a large finned heat sink which measures about 3" x 4" and I am assured will fit the bill.

I do belong to the LE club which, believe it or not has a membership of around 1,000! They have been established for years and acquired engineering drawings and many special tools from Veloce when they went bust in 1971. They also run a comprehensive spares service which makes the LE very easy to restore and maintain.

The LE was used prolifically by police forces during the transition from bicycles to Panda cars. It was felt too dangerous for riders to salute senior officers and so they would nod to a senior officer as they rode past. That is genuinely the reason they became known as Noddy bikes!

Thanks again for all the contributions to this thread.

 

[Danger]

I can't say as I've ever seen anything quite like that before. It's very cool and very weird at the same time. The condition looks mint in the photo, though. Good job.
Thanks for the explanation of the name.

 

[Charlie Weeks]

Nick

I have just read your post regarding your LE Velocette. I have an early Valiant I intend to do something similar to you i.e. fit a Miller police alternator. The standard Miller unit gave a feeble 42 watt so the 80 watt of the police unit will give a welcome boost. However, I was intrigued by your remarks about how poorly the converted to 12 volt operation. Is this change over effected simply by add a second 6 volt battery and changing all necessary components or was a more sophisticated solution sought by rewiring the coils to 12 volt operation? I am not an electrical engineer so I cannot think why the Miller unit was so bad. Was the police unit already 12 volt.?
If you haven't already got a 6 volt regulator I think Paul Goff can help you and he also sells 6volt quartz halogen bulbs but I don't know how you can fit the one he offers into the old British Prefocus headlight rim.