12 Volt Vs 6 Volt Generator

[Dynamo Regulators Mike]

Good (Friday) morning all. Or Happy bun day as my wife says.

Snowbeard: as Beezalex said main advantage of using a DVR2 (or other electronic unit?) at 6V is fit and forget reliability. Voltage regulation is accurate promoting long battery life. You can purchase direct with card/PayPal on the website. (Note to moderators: he did ask)

Thanks for the field winding details. I am inclined to the belief that the double resistance field winding is a bit higher than ideal as well. Something like 30% extra turns ought to give adequate Amp.Turns for near saturation flux at 14V without wasted current. Resistance would be about 4.5 ohms. My estimate is that about 20% extra armature turns ought to provide a good compromise between maximum safe output current and higher cut-in speed. This based on same maximum armature dissipation at with standard 6 V, about 6 Amps 80W.

Result of the increased turns should be similar cut in speed as with Hawker 3:1 belt drive, but no fear of over revving dynamo if using sustained high engine revs (which I don?t). Less power available though. But another point is that Lucas output rating is for a nominal power, at defined modest speed. Not at all the same as maximum safe available power which as far as I know is not mentioned anywhere by Lucas.

I don?t know too much about the current limiting characteristics of the mechanical regulators, but  the 2 bobbin regulators has a series winding to reduce V reg at higher current drains. No idea how well this works in practice. Presumably the 3 bobbin types perform much better in this respect.

Cheers all
mike

[BSA_54A10]

Snowy,

1) forget the battery tender. They do a reasonable job on trucks & tractors but seem to cook motorcycle batteries.
I use an old mechanical time switch ( you know the ones you use to fool the burgulars) . I set it for the smallest time interval which is 15 minutes, plug the battery charger into i and have never had a problem in the past 20 years.

2) modern batteries are a real work of art about 40 % of the weight of the old ones and about 5% as durable.
Once the generator is working properly a high discharge gel cell is the way to go. If you need the higher capacity then get 3 spiral wound single cell batteries and run them is series. They will actually fit in the old battery hole.
Once a new battery has been allowed to go dry it is next to impossible to get the plates to activate ( they oxadize when exposed to air and passivate if allowed to go dry. God forbid if you ever short one out this will usually cause the battery to fall apart internally

3) clean up the terminals every where and then apply either grease or something to prevent them corroding you can loose 2 Volts ( or more ) from dirty terminals and on a 6V system that is a real large amount.

I won't go on about the ganged spade & liquid electrical tape but I can not sing their praises enough. I slap the liquid electrical tape on just about every contact & terminal that I will not be regularly undoing it is real good stuff provided you did a good job cleaning the contacts before application.

Now as for lights.
I fitted a VW reflector ( from an old Kombi wagon ) into the back if the Lucas lamp . This allowed me to use the QH VW 6 V 35/45 W headlamp globe and I would never change them a truely brilliant light that had run without problem for over 10 years till I finally killed the engine.
The lamp was then transferred to the WD B40 after a dozen or more old Lucas prefocus globes parted company between the glass & base and gave another 12 years brilliant service till it was stolen ( with the rest of the bike). These bikes were daily transport and I can only remember changing the globe once. Down here in Oz the VW globe is still current stock  but Lucas type globes come only from specialist shops.

[trevinoz]

I finally got around to measuring the  test speed of my generators.
Unloaded is approx 2900 RPM and loaded would be slightly lower.
With 11 tooth generator sprocket, this equals 2367 engine RPM.
With 13 tooth sprocket, equals 2788 engine RPM.
Road speeds are approx. -  A10 SA - 39 MPH,  A10 PL - 40 MPH,  A7 SA - 34 MPH,  A7 PL - 35 MPH.
Pre '49 long stroke bikes with the E3H generator which has a 13 tooth sprocket, - 41 MPH.
The 12V generator reaches the regulated voltage before this speed but the 6V doesn't reach regulation.
  Trev.