Bodywork, Paint, Interior, Trim, & Wiring

I tried driving the pancake fan under the electronics package with the rotor control signal from the regulator and it worked great. The fan draws 1/4 amp so it increases regulator output by probably about 33% if the full current draw of the rotor winding is 3/4 amp. But that winding is less than 12 ohms resistance, probably closer to 3-4 ohms and discounting inductance would mean about a 3-4 amp draw at full charge and 1/4 amp is less than 10% of that. So I doubt that burning out the regulator will be a problem. I'm willing to chance it.

This way with the ignition on but the engine not running the fan does not run. At idle the fan creates quite a nice breeze past the parts while charging at 10 amps, and at initial startup the alternator still pegs the 50 amp ammeter. Voltage output is steady at 14v with no adjustments made. And the harder the alternator charges, the harder the fan will run.

Now obviously measuring the temp to control the fan would be better, but this works without any extra wiring, sensors, or controls. Dead simple in fact, simply wire the fan across the field winding. Better still, I believe it'll work just fine with Fred's stationary winding setup.

Jim

Hey Fred, I got a box in the mail today, something with a rotor in it looking frighteningly similar to yours! That's a hefty rascal, isn't it?

So as soon as I get a chance I'll see what bearings I have that'll work and give this a try. Pretty precise fit between the rotor and the end plate of course.

Jim

No problem Jim,
I figured that you would get to it long before I would.

Cheers
Fred

I hope so. For the next couple weeks I'm pretty tied up with working on the 3D printer and then wiring the MG when I can but I'll look for the odd moments to work on the bearing bores.

Incidentally, the control package worked out pretty nice and I built an aluminum sheet metal cover for it which I plan to anodize some time this winter. It vents the fan exhaust out the back and acts as a heat shield from the headers.

Jim

Fred, you might hold on to the field winding for that alternator if you still have it and it's any good. That'd strike me as a necessary part. I have yet to look at the number of poles and diameter to see how they compare to others but I'm not sure there's very much interchangeability there.

Jim

Sadly, that stator has left the building.
The rotor size is pretty standard for a Bosch alternator so shouldn't be too difficult to find a stator that would fit.
There's a lot of meat there so you could turn it down to fit if needed.

Cheers
Fred

A bit more info:

The Bosch rotor would have to be cut down close to .300" (8mm) to run inside the Delco S10 field coil, probably inadvisable. The Bosch unit is simply massive by comparison, and against a Denso rotor? That looks like a toy. It's also about twice as deep as the S10. I didn't measure it but it makes me wonder if there might not be a smaller version of that Bosch unit that would be more suitable for our use?

Also, the Bosch is a 14 pole rotor where Delco, Denso, and Ford are 12 pole so the field windings would not work anyway. Perhaps that is a function of the larger diameter.

Jim

The Stator doesn't care how many poles that the rotor has Jim. It's actually to your advantage to have more as it makes the stator think that the alternator is running faster than it is. That allows more charge at lower rpm's.
That rotor is pretty stout so taking 8mm off of it shouldn't be a problem. I can't remember it's actual diameter, but if you could measure it for me I'll check my stash of alternators for a stator that is close.

Cheers
Fred

I measure it at 112mm or 4.380" diameter. The GM's seem to run close to 1/8" clearance on the diameter, which seems like a lot to me. My concern about cutting it down was more about losing magnetic flux (because or the reinforcing ring) than strength, I'm sure it's plenty strong.

About the pole number, yeah, I do think it makes a difference on the count, or at least can maybe depending on how the stator is wound. Normally I think the stator has three times the number of poles as the rotor so each winding lines up with a + or - pole on each winding at the same time so that the voltages add. Otherwise I think the poles on the stator would be fighting each other.

But there could be other ways to wind it and I'm no authority.

Jim

Jim, in the theoretical world the pole count of the rotor vs the pole count of the stator does matter.
In the real world it's a different story. If the rotor poles matched the stator poles the alternator would howl like a siren. And break down the winding's very quickly. Even when mismatched the alternator is still very noisy. That's also why the GM alt's, as well as others, have such a large clearance. Less engineering required to keep it quiet.
So the fix is to taper the rotor poles so that engagement of the two is gradual.
It's not perfect but this reduces noise and vibration under load. And has the advantage of increasing the average efficiency.
Albeit at the expense of peak efficiency. A lot of which can be reclaimed with a lesser clearance.
I agree that the reinforcing ring is a deficiency, but a necessary one as it joins the two forged sections.
I think that the massively increased field coil power more than makes up for that shortcoming though.
I'll check through my carefully archived vintage automotive parts supply (junk pile) this weekend to see what might fit that rotor better.

Cheers
Fred

I found a bunch of stators that will fit for you Jim.
The easiest one to find is the mid 90's and newer bosch 120amp alternator. It came standard on quite a few European cars. BMW, VW, Audi, Volvo etc.
Should be an easy find at a wrecker.

Cheers
Fred

Cool.
I'm still going to be tied up on the 3D machine for awhile but I'll get back to it as soon as I can.

Jim