Alternator clutch

[Festy46]

I was wondering if anyone has ever seen an alternator clutch? It would be like the clutch on an air conditioning compressor. When you needed a little extra power, you could put the alternator in "neutral". I've found an electric water pump. If I could find a clutch for the alternator, then every horse power could be used to move the car.
John

[FestivaBiker1971]

just put a switch in the field wire to the alt. when you turn off the field, the drag from the alt goes away, because the rotor isn't generating a magnetic field.

[spec]

FestivaBiker1971, which one is the field wire? (B,L or S). That sounds like a cool idea... maybe hooked up to shut off the alternator when at full throttle. The battery should have plenty of juice for short sprints.

[SimonTuffGuy]

Moved to the correct forum...

Simon

[Festy46]

just put a switch in the field wire to the alt. when you turn off the field, the drag from the alt goes away, because the rotor isn't generating a magnetic field.

I tried that. It doesn't work. Apparently the alternator with the internal regulator works like the old generators that had to be polarized before they would charge. Once it receives a charge of electricity, it continues to charge even when you remove the field wire. The field wire "feels" the charge in the battery and regulates the current accordingly. When you remove the field wire the alternator "thinks" the battery is totally dead and goes to maximum charge defeating the whole purpose of killing the alternator. I bench tested an alternator and I couldn't get it to stop charging as long as the pulley was rotating. The Festy alternator has some sort of internal connections that I think are keeping the circuit alive. Possibly an AC Delco with internal regulator might work that way (field wire removed), but then I would be getting into fabricating brackets to fit.
John

[glacius182]

as long as the pulley was rotating.

Even if there's no field in the rotor, the rotor is still magnetic that's why there's still current. Even if the rotor is not magnetic the inductor will create a magnetic field that will create electricity. There's nothing you can do about it!

[FestivaBiker1971]

law of Induction says that a current passing through a conductor generates magnetic flux line around that conductor. Conversely, a magnetic flux line cutting through a conductor generates electron flow in that conductor, with its polarity equal to the pole of the field. You're right, I didn't think about the Festy alt when I made my recommendation. I was thinking of older Ford externally regulated alt. When I open the field wire to them, they go into a free-spin mode, minimal drag (old dragstrip trick). I'll research how to kill the field in the Festy alt. none of those wires are field wires. If I remember correctly, It has a batt connection (other than the output terminal) a stator tap and an indicator wire. Opening the stator tap and opening and grounding the indicator lead should kill it. Don't do it yet, let me check my wiring tomorrow.

[FestivaBiker1971]

ok, i was close. the three wires coming from the alt (according to a 1990 evtm) are: batt output (large white), batt reference (18ga red) and indicator (18ga black/red). the red and bk/red wires are in connector c104, the two pin connector on the alt. if you open the red wire, and open then ground only the alt side of the bk/red wire, that will essentially kill the rotor field. the rotor will get ground through the indicator wire as well as the regulator, canceling the field. opening the red wire prevents damage to the reg. CAUTION: if you ground the wrong side or both sides of the bk/red wire, you will blow the METER fuse (10A). hope this helps.

[Festy46]

Thanks Jim. I'll give that a try when the weather gets a little warmer. I just can't get in the mood to work on engines when the temperature is -5 F.
I'll see how tough the competition is this year. Last year about 1/2 the field was Escorts and we could easily kick their butts. Toward the end of the year, guys were discovering the GM Quad 4's as the hot set up. With a good driver behind the wheel, those Quad 4's are tough to beat. If I need to squeeze every hp into driving the car, I was thinking of eliminating the alternator completely and going with a deep cycle battery and charging it for each race.
John