Hello.
I've traded junk for junk with a couple of home-builders and one of
the things I've picked up is an alternator of questionable parentage.
It is 0 TSOH from an alternator shop, automotive with no labels.
The guy told me that his partner got it with "aircraft diodes"
(whatever that means).
Not much . . .
It has a larger pulley on it from an AC generator. I took it to an
auto parts store shop and had it tested (good) and we determined
that it is a 60 amp model similar to what was used on early 70's
Fords (Mopar). It has connections for Field, Stator, and Bat.
This is a real pig compared to the Nipon-Dienso machines
B&C is selling.
Question 1: It tested out OK, but when I measure the resistance
---From Field to Ground, I get a *very* low number, almost like a
short. Am I missing something? What keeps this from popping
the Field circuit breaker when you 1st turn on the master switch?
How low is low? Field resistance of a 14 volt alternator is
generally in the 3-4 ohm range. A digital multimeter might
read this low of a resistance accurately . . . very few
low cost analog meters will do it.
Question 2: In the auto diagram, the only thing they use the
Stator connection for is to run the electric choke (?!?).
Yes . . . it applies heat to the choke's bi-metal actuator
ONLY when the engine is running. If one simply hooked the
choke heater to the ignition switch, it would begin to heat
up even if the engine were not running.
I asked "Are you sure they don't mean choke as in filter?"
The guy seemed sure this was the carburetor electric choke.
Correct.
If so, does the Stator need to be connected to anything?
No . . .
Question 3: The fan is of course backwards.
Don't worry about it. It's a centrifugal fan and is
only slightly affected by direction that the vanes are
pointing . . . in fact, if you check out the blower
in your furnace, you'll find that the blades on the
blower point FORWARD with respect to rotation.
With the baffling in my cowling, both the front of the starter
and the alternator will be in the high pressure cool air and
the rear of each in the low pressure hot air. In normal
operation the fan would be trying to suck hot air against
the cowling pressure. Sense there is some cooling pressure
even when the plane is just taxiing and the cool air will
blow from front to rear, do I need a fan at all?
Yes. Leave the existing fan in place. You may want
to reduce pulley size so that you can get full output
at taxi RPMs . . .
Bob . . .
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