6 Volt generators question

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kell
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6 Volt generators question

#1

Post by kell » Sat Jan 14, 2006 10:26 pm

Description: Do six volt generators work the same way as 12 volt generators?

Do six volt generators work the same way as 12 volt generators? I understand there was a configuration with three brushes that works differently...



Cotten
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Re: 6 Volt generators question

#2

Post by Cotten » Sun Jan 15, 2006 3:37 pm

Kell!

I'm electronically challenged, but three-brush generators were all 6v with independent fields, controlled by the position of the third brush, and a simple relay switch.
Two brush units, both 6 and 12v, have the fields in series, and rely upon a true regulator.
The three brush units are convertable to two-brush, and marginally even to 12v, but I know of no advantage of converting a 12v back to three brush.

kell
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Joined: Sat Jun 19, 2004 2:58 am

Re: 6 Volt generators question

#3

Post by kell » Sun Jan 15, 2006 11:54 pm

Thanks for the information.

FlatHeadSix
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Re: 6 Volt generators question

#4

Post by FlatHeadSix » Mon Jan 16, 2006 4:37 am

Kell,
I'm not sure how much detail you need or where you are headed with this question but I'll ramble for a minute, stop me if I get too deep.

Like Cotten said, the 3 brush units are all 6 volt. The 3rd brush is actually the current regulator and can be adjusted to produce more or less current. They mount in a slotted plate, moving the brush closer to the relay terminal will produce more current. Voltage is controlled by the field windings by design. The model 32 and 52 were designed with a low enough output that control was not a problem. The 32's had two different field coils and are independent as Cotten said, only one is energized with the ignition switch in the first position. The second field coil is only energized when you switch on the lights. The model 52 is essentially the same but both the field coils are the same instead of having a lower output shunt coil.

The problem most folks have with the standard 6 volt units is that they were never intended to produce enough current to power a lot of extra stuff. An easy way to explain it is to compare it to a water pump or an air compressor, voltage is the 'pressure' and current (amps) is the 'flow'. When you open a water or air valve and start a flow the pressure drops, the wider you open the valve the more the flow increases and the pressure drops. If you want to maintain the same pressure at a steady or increased flow you have to speed up the pump. In a generator you do this by putting more current into the field coils which produces a stronger magnetic field around the armature and produces more current. The 6 volt units are capable of producing huge amounts of current if you bypass the internal regulation but they will self destruct; energy = work = heat. The armature melts down, literally.

So, you can take the 3rd brush out of a 32E or 52 and connect a 3-unit regulator instead of the relay but when you turn on the spot lights and all the bullet lights on your cheese cutter and those butt lights under the solo seat the poor generator will try to keep up, but not for long. The police units had a fan blowing air on the end of the armature but that wasn't really a solution.

The reason alternators are so much better is that they draw the current off of the stator instead of the rotor thru a set of brushes. If you ever looked at generator under full load at night with the cover off you'll see that there is 'ring of fire' around the commutator on the end of the armature, no matter how good the brushes are.
Bottom line is that the 6 volt units are what they are and you really can't do much to improve them. They were fine for what they were designed for but they have limits.

Cotten
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Location: Central Illinois

Re: 6 Volt generators question

#5

Post by Cotten » Mon Jan 16, 2006 2:47 pm

Just for clarity:

3-brush systems discharge at modern highway speeds, making them impractical for daily use.

2-brush 6v systems with a decent battery will quite comfortably push a headlamp, taillamp, and the normal compliment of accessory lamps, such as issued upon sidecars.

12v systems do better by virtue of better batteries.

Spotlamps, however, will always push the total load above the comfortable output of generator systems. Thus your riding time using extra illumination is limited by the battery's reserve. If that gets low, the excessive heat begins to build at the armature.
Spots were commonly called "passing lamps", as they were only intended for intermittent use.

....Cotten

kell
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Re: 6 Volt generators question

#6

Post by kell » Mon Jan 16, 2006 6:11 pm

Panzerama

Somebody asked if I can make a voltage regulator for a six volt bike. From your and Cotten's answers it appears six volters do come in a configuration amenable to control with a conventional voltage regulator or can be converted.

FlatHeadSix
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Re: 6 Volt generators question

#7

Post by FlatHeadSix » Tue Jan 17, 2006 5:52 am

Kell,
All of the 2 brush 6 volt units must have an external regulator, and any of the 3 brush units can be converted to a 2 brush by removing the 3rd brush and wiring the field coils in series. The original external regulators are the mechanical 3-unit type exactly the same as a 12 volt regulator but wound for 6 volt application (heavier wire). The 3-unit regulater has a cut out relay, a voltage regulator and a current regulator.

There is already a 6 volt solid state cut out relay on the market for the 3 brush generators, I have one on one of my bikes and it works quite well.
As I mentioned in my earlier post, if you put a regulator on a 2 brush unit that tries to match the generator output with the load demand it will force the generator into trying to produce too much current and burn up the armature. If you approach a 10 amp output you're overloading the unit.
Like Cotten said, the correct terminology is 'passing lamps', not spot lamps, you can't run them continously or the battery will discharge. In fact, according to the original design specs, if you left home at sundown on your stock '48 pan with a standard model 32E generator running only the standard lighting system and rode all night your battery would be completely discharged by the time the sun came up. They just weren't made to run with the lights on all the time.
I think Cotten may have mentioned in another post about installing a low watt daytime running light, something like the old 6 volt VW's had. You could sacrifice and old CycleRay reflector by sticking a socket for a parking light bulb thru the bottom of it.
Jump in here Mike Beam, this may be a good application for an LED.

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