The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: timbodibble on 02.05. 2010 15:36

Title: help with 6 to 12v conversion
Post by: timbodibble on 02.05. 2010 15:36
HI All - just got myself a 59 SR and i have a question i hope someone can help with.

It needs wiring and currently the dyno is a 6V. I would like to convert to 12V for the lights but im not sure exactly what bits to buy for this. I believe there is a 6-12V converter which also acts as regulator but im not sure how this gets wired in. the only wiring diag i have is the one in the Haynes manual with the FADE set up 4 in/output).

I know i'll need a 12v batt and bulbs, but if anyone can suggest any model nos for the converter and what other gizmos might be needed along with a wiring diag / description, id really appreciate it.

Cheers All

Title: Re: help with 6 to 12v conversion
Post by: a10gf on 02.05. 2010 17:12
Welcome to the forum. (made your post into a new topic).
Not exactly an answer to your question, but unless you really want 12v for some reason, just make sure the charging + battery is in ok shape, and simply get a 6v halogen front lamp. Instant illumination.

Title: Re: help with 6 to 12v conversion
Post by: Triton Thrasher on 02.05. 2010 18:21
There are many 12V regulators made for 6V dynamos.  Most are a bit crappy and discharge the battery at low revs.

I'm told the Manortec DVR2 works bette than most.  I expect it comes with instructions.  I've never used it, but have enough experience to warn you off Boyer's version of a 12V DC regulator.
Title: Re: help with 6 to 12v conversion
Post by: muskrat on 02.05. 2010 21:05
G'day Tim,
              Welcome to the forum.
 I'll second the DVR2. Connects to the FADE wires and fits in the old reg box. I think about 46 quid.
Title: Re: help with 6 to 12v conversion
Post by: Mosin on 02.05. 2010 21:31
Hi Tim,

I did exactly the same conversion on my A7ss a few months ago. I used a DVR2 which is excellent, and I bought all the other bits (battery / bulbs) from Paul Goff, ( I just phoned him up and told him what I was doing and he told me exactly what part numbers etc he recommended. The 6v horn seems to work perfectly well in a 12v system. I've gone for a 12v halogen headlamp and LEDs everywhere else. I also converted to electronic ignition with a Pazon system. The original 6v dynamo seems perfectly capable of supporting all of this using the standard chain drive. The only discernable difference is that the engine needs to be revving a little faster before it begins to charge at 12v. This is not a problem for me as I live on a stretch of dead straight road with a 60mph limit and it's 5 miles in either direction to the next village, but it might prove a problem if you live in a built up area and only use the bike for local short runs.

Good luck!

Title: Re: help with 6 to 12v conversion
Post by: groily on 02.05. 2010 21:58
Can't go wrong with the DVR2 a new battery and some bulbs from Goffy or wherever. Yup, the standard dynamo has to spin a bit at 12v to get to cut-in voltage, but Mosin reckons it's OK with a chain drive and I know DVRs are good at 12v with pinion-drive (not alterable!) on other bikes. A belt would up the dynamo rpm a bit and is a good mod anyway when the chain clatters to its life's end and has eaten enough aluminium. If you wanted to go even further, 'fine-wound' so-called '12v' field coils and armatures are available too, which preserve original cut-in speeds. I've one bike with that set up and have to say it is pretty impressive.
On TT's point, it's true that a lot of regulators allow a discharge from battery to armature at low rpm - same as the mechanical boxes do - but DVRs don't allow it. It's one of their nice features. Along with the fact that the three I've got have worked faultlessly from Day 1, one at 6v, one at 12v with fine-wound bits, one with standard original windings. Can't fault the things, and dead simple to fit. No mods needed.
Title: Re: help with 6 to 12v conversion
Post by: trevinoz on 02.05. 2010 22:07
            I will take you to task over your statement regarding the mechanical regulator allowing a discharge at low revs.
If it is set correctly this will not happen.
A properly set regulator will give years of trouble free service.
Title: Re: help with 6 to 12v conversion
Post by: MG on 03.05. 2010 09:57
Trev, couldn't agree more.
The mechanical regs work a treat, also in combination with the electrically delicate sealed gel batteries.
Once refurbished and set up properly, you can simply forget about it.
Title: Re: help with 6 to 12v conversion
Post by: bsa-bill on 03.05. 2010 10:39
I have an electronic one for my project ( which is now 12 volt )
However I have never had any problems with Josephs mechanical wonders and have never tried to adjust them - I think this is the secret *smiley4*

All the best - Bill
Title: Re: help with 6 to 12v conversion
Post by: groily on 03.05. 2010 19:00
Take my hat off to you Trev et al if you can get mechanical boxes to cut-out that well. I've found they tend, because the cut-out voltage is set lower than the cut in (to avoid having the thing flutter if it can't decide whether to connect D to A or not), to allow a 1-2A discharge at tick-over. I don't pretend to be an ace at setting them up, but a lot of folk would, I think, say the same. I also think electronic boxes prolong dynamo (and battery) life by managing field input and charging rates better than any mechanical box ever could.
I've given away all my CVC boxes now to people who prefer them, along with a few selenium rectifiers and other clobber from the era of constant breakdowns.
No mechanical boxes, no 3 wire alternators, no original rectifiers, no zener diodes even round here. Just solid state regulators for dynamos and ditto reg/rectifiers for alternators.
I'm not one-eyed enough to believe that the original bits don't work - I know they can and do and have had quite good service from them over the years. It's just that not being a purist, I prefer leccy bits that are fit and forget as I need lights and stuff quite a lot of the time.
There are enough things to do in a shed . . .
One of which is to charge the battery on my one dreaded modern bike from time to time as it never goes anywhere.
Title: Re: help with 6 to 12v conversion
Post by: MG on 03.05. 2010 19:40
as always, it is down to personal taste really.

To me, running an old vehicle with old equipment (mags, dynamos, mechanical regs, etc.), is just part of the fun.
I agree that fitting a new item in many cases is the easier and faster solution, but no way for me as a purist.

Cheers, Markus
Title: Re: help with 6 to 12v conversion
Post by: groily on 04.05. 2010 17:04
Totally respect that Markus, I genuinely do. And is why I've happily given away my old bits to people who prefer to stay with things the way they were made. Horses for courses as you rightly say. Just as I respected one of my mates who, once we'd got his dynamo going (a beautiful 3-brush 'Magneto France' creation that makes our Lucas ones look like Toytown devices), declined an offer to hook it up as a 2 brush to a solid state box in the interests of night-time running. Quite right, as it's a rare bike it's on and he'd have felt a cheat.

Being a cheapskate is another reason I like modern upgrades myself though - costs more to get a CVC rebuilt properly than to buy a DVR2, and the replica mechanical ones aren't, allegedly, much to shout about (although I have never had one).

In similar heretical vein, I even set aside (not junked, mind!) the original Rotax dynamo and CVC on my pre-war car in favour of a 30 Euro scrapyard alternator driven by a fun-to-contrive set of pulleys off the crankshaft nose . . . Hundred and Ten Watts for 2 headlamps etc and the coil didn't seem to cut it somehow, especially as the output started to get hit and miss despite best efforts - while near-600W (yup!) leaves enough to run anything, including 60W halogen lights and some add-on indicators that save your bacon in the dark. Cheap and effective solution, discounting the time to make the drive train. Very very bad, I know - but works so well. The next guy can always swap things back if he wants to get the 75-old armature rewound and swap a few wires round to get back to the correct positive earth.
Because all these sorts of mods can be reversed easily enough, I never feel bad about them myself, especially on 'cooking' bikes. Probably wouldn't do them on some piece of glorious unobtainium, but nothing in my shed comes into that category by a very long shot.

Never ditched a magneto though, and never would, so with you there 100%. Separation of Powers between charging and sparks seems to me as important as between, eg, Government and Judiciary. My only (alternator) bike that could have one but unhappily doesn't, might get one yet. It will if (when?) the Boyer system gives up - which every thread on that topic I see makes me fear it might. Fingers firmly crossed, but it's defied the pessimist in me for a few thousand km so far.
Here's to the catholic nature of the classic movement . . . as it's just nudged beer-o-clock . . .