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Discussion Starter #1
Hi all,

Triumph T100 -54 (rigid chopper)

I've just repaired my old Lucas E3L by replacing the stator, coil and brushes with a new 12V-kit from british bike bits (it used to be 6V). The bike was bought with a faulty generator and 12v bulbs and battery. The previous owner seems to have just given up with the dynamo, snipped the cables and settled with charging the battery in between each run instead to have lights. No can go for me!

The bike is wired bare bones style with only head light, tail light and kill switch. No regulator or any other electrical components besides the ignition (Lucas K2F, which has its own circuit and is not affected by battery/charging system). I'm planning on getting the bike even more "bare bones", so I'm ditching the battery. What I'm trying to figure out now is what kind of regulator I need (can't find any proper DC regulator online??) and if I'll be fine without a capacitor?

I've got the dyno set up on my test bench. After the repair it's delivering 12-20 volts DC measuring with the D and F-terminal bridged. So far so good! But it needs regulating..
 

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I ran my 69 650 for years on just a "black box" unit that did it all. You have to kick it harder to start, than one with a battery, and you need to keep the revs up at the lights, esp running a headlight. From what I've been reading here, it probably isn't practical to use a modern, high-powered bulb in the headlight. A separate capacitor might help a little.

All black boxes are not created equal though. I had a second bike with a black box that would cut out intermittently. Never left me stranded but was inconvenient. My current arrangement is to run the Mitymax, which has been on there forever, but I also have a Tympanium (not sure of the spelling) on the bike, with wires ready to connect if need be.

images from current ebay search

max.jpg typanium.jpg
 

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Many electronic regulators for dynamos need battery power. I think Boyer sell one that doesn’t. It’s possible that the DVR2 type also doesn’t. Check with the seller or maker.

In my experience, the dynamo does not generate any power at all at idling rpm. Are you ok with the lights going out when the revs drop to idle?
 

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I guess that I need to qualify that I've always ran points on my Meriden twins. The old Triumph alternator "runs on the come" and does not need any exciter current, but you do need to give it a healthy kick to start. If you have an old Zener diode, you don't even need a capacitor, but be prepared to really boot it and keep the revs up - That's more of a getting home scenario. With the black box you get some capacity. I'm old and my knees are going fast, so I recently added a tiny battery just to help that initial spark along. But I'm basically bare bones where I can get away with it.
 

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Also would need the stock rectifier in addition to the Zener, as absolute minimum, and a new Sparx capacitor, to go old school, but the black box is so much tidier. Four wires and place it anywhere. Not going to fry it with a stock alternator.
 

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Discussion Starter #8
Thanks for all your replies!

Since I'm running a DC generator and a K2F points ignition spark shouldn't be affected by battery or no battery.

I have ordered a boyer regulator now, which according to the manual is OK to run without a battery. It really wasn't easy finding a regulator that wasn't AC and therefore also not a rectifier. Boyer had what I needed!

 

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Aha, the light finally goes on! I thought that dynamo was just being used as a euphemism for generator.
But then couldn't you just use a Zener, since you've gone to 12 volts
 

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Aha, the light finally goes on! I thought that dynamo was just being used as a euphemism for generator.
But then couldn't you just use a Zener, since you've gone to 12 volts
No, you can’t use a Zener, because it would make the dynamo work too hard and overheat. Regulation by shunting the output is for permanent magnet alternators.

The dynamo has to be regulated by restricting the exciter current to the field winding.
 

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Got it. I'm truly sorry to have run on about the irrelevant, but indulge me one last crazy question. If the Zener would tend to draw more out of the dynamo than it could deliver, would it be possible to toggle to a Zener at idle, in order to get the idle output to deliver high current at low revs, if just on a momentary basis?
 

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It may be possible to get some low rpm power out of a dynamo by feeding the field coil some battery current, but whether more would come out than you’re feeding in is dubious in my mind.

I’m not clever enough to actually work it out.
 

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When I was young, so talking 60’s Brit bikes, many people I knew used no battery, just the blue capacitor on a spring. Some, like myself, kept the battery in place even though it probably couldn’t hold much of a charge. I rode at night, working the late shift, and it got me home.
 
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