Conversion - 6v to 12v

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
rhunter
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Joined: Thu Dec 12, 2002 12:00 am
Location: LOTHIAN UK

Conversion - 6v to 12v

Post by rhunter »

Could somebody give me a simple guide making the conversion from 6volt to 12volt on my newly restored 1952/3 AJS model 18s. Can I still use the restored 6 volt dynamo to generate 12 volt and should I use a new heavier wiring loom?......many thanks...Rob
JimFitz
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Location: Kent, England

Re: Conversion - 6v to 12v

Post by JimFitz »

rhunter wrote:Could somebody give me a simple guide making the conversion from 6volt to 12volt on my newly restored 1952/3 AJS model 18s. Can I still use the restored 6 volt dynamo to generate 12 volt and should I use a new heavier wiring loom?......many thanks...Rob
Yes you can use the 6v dynamo but it does need to spin faster to give a decent charge at 12v which may not be possible depending on your style of riding and the type of roads you use. Add to that the cost of a 12v control unit and new battery and you are probably better spending your hard earned on a set of 6v LED bulbs.
Although the night time performance of the LED headlamp is probably not quite as good as a filament bulb, it will allow you to leave the headlamp on during daytime running without flattening the battery and avoid the SMIDSY car drivers.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
rhunter
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Location: LOTHIAN UK

Re: Conversion - 6v to 12v

Post by rhunter »

Thanks Jim....sounds like clever advice. I was thinking about daytime running of headlights to save my life from other road users ....where can you find 6v led bulbs?....Rob
Groily
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Re: Conversion - 6v to 12v

Post by Groily »

In theory you can, if you would be happy with the slightly higher engine speed required before the dynamo starts to charge at the higher voltage.
However, I personally probably wouldn't do it to a 'short' E3N (yours, if the Lucas parts lists are to be believed and what you have is original) or E3H or AR dynamo if you have one of them, but I'd consider it on the longer 60W E3L. Not sure if one of those would clear your gearbox casing though.

If a long dynamo would go on, or is already on - or if you want to do it anyway with a short one - all that is needed to do the conversion is:
a) A new regulator unit. (The best UK option is probably the DVR2 from Dynamo Regulators Ltd: http://dynamoregulators.com/dvr2.php)
b) A 12v battery (say 6Ah and up)
c) 12v bulbs (or, if LEDs, may be the same items, as many are rated 6-24v)
Some recommend a 12v horn, but I've never swapped - as long as you don't keep your finger on the button for long continuous blasts the old one will be OK, but the tone will alter.

A standard E3L dynamo with DVR2 will support continuous loads in excess of the original 60W rated output. Some people regularly load them to around 80W without mishap, even supporting modern electronic ignition systems.

I have had three dynamo bikes running with a standard E3L '6v' dynamos and DVR2s for a combined total of about 25 years between them (and many more years before that using other 12v regulators) - but they are all twins and so rev a bit more. If you're in a lot of traffic and like very low rpm, then the additional rpm might be a deterrent for a single, even with the longer dynamo if it would fit/is fitted.

As an option you can swap an E3L (Long) armature and field coil for finer-wound '12v' parts which are available new, UK made. (Not an option for short dynamos though as no parts are available off the shelf.) If you did that, you'd have the dynamo starting to charge at about the same rpm as originally. You'd need the new regulator though, just the same.

Converting from 6v to 12v shouldn't affect the harness bar the change in regulator connections. With twice the volts there will half the amps running around, and so in fact the wires could be thinner if you were starting from scratch - and any fuse reduced in rating.

My gut feeling is that you probably have the smaller model dynamo . . . but I have seen singles with long dynamos fitted, using later one-piecemetal dome brush plate covers to get round the clearance problem at the gearbox - just!

LED bulbs, as mentioned by Jim, give a nice white light and require very small current - Good News. Available from eg http://www.dynamoregulatorconversions.com/ or off e-bay now I think. But, my experience so far, having fitted three of them on various bikes, is like his - the spread of the light isn't great on dip beam on unlit roads and the main beam has a tendency to point to the sky on mine. But they are getting better, they say. I've just reverted to a 45W halogen on one bike for the coming winter.
JimFitz
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Location: Kent, England

Re: Conversion - 6v to 12v

Post by JimFitz »

Groily wrote: LED bulbs, as mentioned by Jim, give a nice white light and require very small current - Good News. Available from eg http://www.dynamoregulatorconversions.com/ or off e-bay now I think. But, my experience so far, having fitted three of them on various bikes, is like his - the spread of the light isn't great on dip beam on unlit roads and the main beam has a tendency to point to the sky on mine. But they are getting better, they say. I've just reverted to a 45W halogen on one bike for the coming winter.

http://www.dynamoregulatorconversions.com/ is where I bought mine although you may need to change the polarity of the system to suit some bulbs. I use the "double dipper" headlamp bulb and I have to agree with Groily, the beam pattern is not quite as good as a filament bulb.
As far as the loom is concerned, if you are fitting a new one then go for the biggest wire that you can (within reason). I always make my own looms and I use 2.5mm throughout. I also run extra earths to the headlamp and tail lamp. Smaller wire gauges will carry the current required but the higher resistance will cause a volt drop and you want the maximum voltage you can get at the bulb rather than losing a percentage warming up the wiring loom.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
rhunter
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Joined: Thu Dec 12, 2002 12:00 am
Location: LOTHIAN UK

Re: Conversion - 6v to 12v

Post by rhunter »

Thanks gentlemen....auto electrics is not my strong point so all this information is extremely helpful. I did a dynamo output test with a 12 volt bulb and it did take fairly high revs to give a good glow....certainly nothing at tick over speeds. I also do not intend any night driving if I can help it so that may be crucial whether I decide to convert......well I may just give it a go!.......many thanks.......... Rob
SPRIDDLER
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Re: Conversion - 6v to 12v

Post by SPRIDDLER »

There's a simple guide which answers all your questions and provides everything you'd want to know about how to convert 6 to 12v (if you really want/need to do it :roll: ) here on James' Matchless Clueless website:

http://matchlessclueless.com/electrical ... onversion/

Plus lots of other leccy and mechanical good practical stuff.
'There is a tide in the affairs of men
Which taken at the flood............'
JimFitz
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Location: Kent, England

Re: Conversion - 6v to 12v

Post by JimFitz »

rhunter wrote: I also do not intend any night driving if I can help it so that may be crucial whether I decide to convert......well I may just give it a go!.......many thanks.......... Rob
If you do not intend to do much night riding then the poorer performing headlamp beam will not be too much of an issue and there is little point in going to 12v. I would definitely stay at 6v and fit LEDs and you can leave them on all time during daylight riding for safety.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
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Expat
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Re: Conversion - 6v to 12v

Post by Expat »

Good.....that makes me feel more positive about sticking with 6v.

Thanks Sprids and Jim.
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
MartynG
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Location: Victoria, Australia

Re: Conversion - 6v to 12v

Post by MartynG »

rhunter wrote:Thanks Jim....sounds like clever advice. I was thinking about daytime running of headlights to save my life from other road users ....where can you find 6v led bulbs?....Rob
Another reliable and knowlegable source of all things electric is Paul Goff; here is a link to his web site http://www.norbsa02.freeuk.com/

Martyn
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