OT-Automobile alternator rotation direction

I'm thinking that all else left alone, it probably doesn't matter which
way the shaft of an automobile alternator is rotated since the machine
produces ac which is then rectified to create a polarized dc output.
Am I right about that?
The question came up just now when eldest son and I were kibitzing about
this week's "Car Talk" puzzler:
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Thanks guys,
Jeff
Reply to
jeff_wisnia
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The only issue should be the cooling fan. If it spins the wrong way, it won't cool anything.
Reply to
Cydrome Leader
The wear on the slip ring brushes may be different.
And I agree with your thinking as to the Puzzler.
Reply to
David Lesher
My drill is reversible, so it doesn't really matter anyway...
Reply to
Joe Pfeiffer
And all my 120 volt drills turn only CW. (That tells ya how olde they (and I) am.
Son just pinged me to say that if you ran the alternator belt over the alternator pulley and then over the drill chuck you could point the drill in the appropriate direction. That may be the answer the Car Talk guys are looking for, as it's not likely there'd be enough room under the hood to connect the drill through a socket directly to the alternator shaft nut.
But, you could always unmount the alternator and.......
Jeff
Reply to
jeff_wisnia
I may be splitting hairs here, doesn't the battery have to have a little bit of charge in order for the alsternator to be excited enought to generate?
Reply to
Nutz
I wonder if hat's the correct approach. In my cars, the alternator pulley ratio apears to be at least 3:1. So at idle, the alternator is spinning at around 2400 RPM. My drill won't do anywhere near that speed. And running the belt over the chuck will turn the alternator pulley slower than the drill.
I'd just take the extension cord and/or jumper cables and wire the generator in series with the alternator output. The alternator diodes will rectify the AC. Then, throttle the generator up slowly. At a low RPM, its voltage output will be low enough to charge the battery.
Reply to
Paul Hovnanian P.E.
My answer is first look for a DC output from the generator. Many have them.
Either direction will do; with the hood open and the engine off the generator will be in a far cooler enviroment.
I wonder how hard you can push it anyhow. A 100A car alternator is outputting ~1.5KW. [15v*100A] It needs say 2KW in to deliver that. That means the drill would need to produce 2KW. It would draw say 2600 watts. Can YOUR drill produce that? For how long? (I think it more likely you can get 600 watts ergo 20A out.)
So I think it fair to say that while you can spin the alternator and get some charge out of it; it's going to take you a while.
The other question is how to connect it up. Given we have a roll of duct tape... wrap the pulley and the chuck in same; and use friction drive? If it's a flat belt, you could drive it from the chuck...maybe.
Reply to
David Lesher
Maybe. But often the soft iron contains enough flux to self-excite. And a ""dead"" battery isn't usually. Turn off the headlights, wait 10 minutes, and you'll likely get several volts out...
Reply to
David Lesher
On Mon, 04 May 2009 16:46:10 -0400, the infamous jeff_wisnia scrawled the following:
Electrically, you're probably right. But the brushes I've seen during rebuilds of most brands (in my previous life) were usually situated to run in one direction only and they'd self-destruct in minutes if run the opposite direction.
"Some kind of builder" wasn't very bright, was he? ;)
I'd run the genset to power up the drill to turn the alternator to charge the battery, even if I had to drill a hole through the radiator support and/or grille to do it with a branch extension and the duct tape.
-- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage. --Mark Russell
Reply to
Larry Jaques
You don't have enough power to turn the engine over (and will refer to the battery as "dead") a long, long time before the juice is too low to run the alternator.
The part of the problem I'm wondering about is getting the belt back on, and tight enough to turn the alternator, with the engine running. Or else you better live pretty close..
Reply to
Joe Pfeiffer
On Tue, 5 May 2009 10:03:41 +0800, the infamous "Nutz" scrawled the following:
It would. Lead acids tend to rebuild naturally after the load is removed, and lights left on would probably only pulled it down to 8v or so, plenty for excitation of the silicon bits.
-- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage. --Mark Russell
Reply to
Larry Jaques
Never happen.... Charge battery; replace belt, and hope it will start. If not, yank belt, and charge 3x as long, try again.
I've tried to think up a belt-unloading scheme using the extra-virgin olive oil, to no success....
I might UNPLUG the alternator while cranking; to remove that load from the system...
Reply to
David Lesher
What load? The alternator isn't producing enough voltage while cranking, to have usable output. The voltage has to equal or exceed the battery voltage before it supplies any current.
Reply to
Michael A. Terrell
So he's gonna build a cabin with an electric drill and a socket wrench? Must be an erector set scaled up, or maybe a metal pole building. Not what I visualize when I think "cabin", but these are modern times.
Joe
Reply to
Joe
On Tue, 5 May 2009 06:06:59 +0000 (UTC), the infamous David Lesher scrawled the following:
Uh, Joe, with a charged battery, you can stop and start the engine at will. There is no need to play around moving fan blades. Hmm, I hope you're not a TEACHER at nmsu...
Oh, no. Charge battery, start engine, stop engine, replace belt, start engine, drive home. Otherwise, charge longer and repeat above.
Oh, and tell that idiot who left his lights on to put the _fuse_ back in so his warning buzzer actually warns him next time, eh? ;)
That might have been a spoof item to take your mind off the real fix.
Huh? If you did that, it wouldn't be charging the battery.
-- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage. --Mark Russell
Reply to
Larry Jaques
On Tue, 05 May 2009 09:12:42 -0400, the infamous Joe scrawled the following:
They forgot to mention his hammah, nailbag, and handsaw. ;)
Look what they refer to as cabins here:
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Disgusting, isn't it?
-- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage. --Mark Russell
Reply to
Larry Jaques
I wasn't anticipating standing there with the drill long enough to fully charge the battery, just long enough to get the engine to turn over. Yeah, leaving it there long enough to really charge would do it...
I am a professor; you'd need to ask my students whether I'm a teacher :)
Reply to
Joe Pfeiffer
That's what I said to my son, but his immediate reply was, "So...wrap that whole roll of duct tape around the drill chuck to increase its diameter."
Yeah, that should work too, and I'd expect the alternator diodes would have a high enough reverse breakdown rating to be able to stand someone doing that, but what if I'm wrong???
Jeff
Reply to
jeff_wisnia
If that is the current puzzler it has been recycled (not like Ray would do something like that :)
The answer as I remember it was to use the generator to run the drill to turn the alternator. I think they slipped the belt off and looped it over the drill chuck.
As normal, I doubt if anyone actually tried to do this, but in theory it should work, eventually...
Reply to
Leon Fisk

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