(OT) Need alternator load-torque curves

How good does it have to be? I'd think a straight line, based on theoretical power multiplied by some fudge factor efficiency number, should get you in the ballpark, at least to within an order of magnitude. (torque would obviously vary both with load and RPM)

nate

Nate, No - it has to be actual measured data, or what a manufacturer claims to be the data so that, at a minimum, the shape of the curve can be characterized similar to what you said. I pretty much know what I expect it to look like, but the problem is there is someone who doesn't believe it, and my drawing my own curve will mean no more than saying it like I already have. It must be data from an independent source.

I e-mailed Gates knowing they'dcertainly have such data for serpentine belt design, but I'm not holding my breath for them to send anything to me or to even respond, modern business being what it is.

Thanks!

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Here y'go:

DS

Oh man! Thanks, Daniel - but it's not what I needed. What I need is a plot with current (from zero, or close to zero, to some high value, maybe the rated current of the alternator) in the X axis and spinning torque in the Y axis. Ideal would be a family of curves on one plot, each curve being for a fixed rpm.

Basically it would be showing engine load increase as alternator output load increases.

What I am trying to get across to a certain someone is that adding an electrical load to an alternator mechanically loads the engine. Of course that is obvious to anyone who knows and believes the law of the conservation of energy, but the light hasn't gone off for this person.

People who don't know better have the idea that taking a mechanical (belt-driven) load off the engine and replacing it with the electrical equivalent load is freeing up horse-pressure. My saying it isn't so and citing the laws of thermodynamics is not registering. This person is going to have to see it in a visual representation of torque (load on the engine) as electrical load is added tot he alternator.

Open to ideas (though I have tried some of my own to no avail)...

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Kee-ryste, you *can't* still be working on this guy:

Invite your, er, friend to start up his car with no electrical accessories running, open the hood, and stand near the alternator watching and listening while a helper turns on every electrical accessory. High beams, heater with fan on "high", rear window defogger, roll down all the power windows and hold the switches in the "down" position, windshield wipers.

Oh, I thought you were designing something and needed to estimate belt load.

I really don't know where you could find what you're looking for, although if you do find it, please post back as I'd be interested to see how close my "educated guess" was :)

nate

Especially effective with an older car that doesn't have an AIS (or equivalent feedback on idle speed).

Heh heh! Yeah I've explained all that to him - even mentioned how V-belts were more susceptible to that, that with a slick or marginally tight one, you could definitely make one slip that wasn't slipping by turning the bright lights on and turning the cabin fan on high. Serpentine belts certainly seem to be less immune to this, especially with auto tensioners, and it's harder to notice engine changes with closed loop control of the idle.

It's funny how that the more our cars are computerized and things close-looped, that variations are so compensated that the guys coming along now loose some of the basic understanding of things that we got just by observing when things were more basic - i.e., if something failed, you knew it, and it wasn't compensated for. Individual laws of physics were more directly and separately observable.

I figured if I could get a hold of a representative plot, I could get the idea across with no wiggle room. He's kind of like aarcuda, but without the "personality", so there's some hope for education there.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Obviously I meant to say *more* immune (to slipping under load).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

If for some inscrutable reason you still feel the need to force this ignoramus to drink, hand him a copy of Stockel and Stockel and walk away.