>According to Bill at B&C, the problem is heat under the cowl. Seems auto
>alternators often do not get enough cooling under there and so they and/or
>their internal regulators go south. Lesson: provide your alternator with
>a supply of cool air adequate to keep it health and happy. There is, of
>course, the issue of "abusing" the alternator electrically which has been
>addressed elsewhere.
>
>Gary Crane
>
>
I'm not sure that "heat" or any other stress can be identified as
the single worst effect on an alternator. I guess I didn't see the
threads on "electrical abuse" of alternators and I'm mystified
by that notion . . . how does one electrically abuse an alternator?
We know intuitively that doing some extra things like a cooling
air source is a "good" thing. Necessary? Without measurement
data we don't know. B&C's ultra-balancing procedure on their
rotors is a strong selling feature . . . not one bearing failure
in thousands of units sold? Necessary? There was no measurements
taken of relative vibration levels versus failure rates for
B&C alternators . . .in fact, no very few B&C alternators figured
into the decision but observations of other automotive conversion
product's problems prompted the rather expensive decision by B&C
to do the ballancing.
Irrespective of the discussions on which alternator or how it's
installed or if one should worry about abusing it, there's a
consideration that transcends all others. Question: After you
applied all the best advice, applied your best craftsmanship
and educated yourself on it's application, are you now betting
anything on the notion that it will never fail? "Never fail"
means 100% reliability . . . like your wing spar or elevator
control push rod.
A nice thing happens when we do failure mode effects
analysis and develop satisfactory alterantives to all failures,
the discussions about "cooling this just right, or not abusing
that" become much less significant. Much of what is brought
forward as advice is based on anecdotal information. Nothing
wrong with anecdotal information, it's the best we have
in many, many design situations but it does not lend itself
to analysis for cause/effect or quantified performance and
stresses. A lot of B&C's manufacturing decisions are based on
anecdotal input. Once you've acquired a component from B&C or
any one else, the prudent approach is to assume that any of these
parts are going to fail anyhow and develop well a reasoned "plan-b"
for the situation.
Reliability studies are conducted on critical components of
machines like the space shuttle and for commercial air transport
of people. Believe me, you cannot afford such efforts on the
convenience accessories in your airplane. I recommend you treat
EVERYTHING electrical as a convenience item, each backed up
by "plan-b" alternatives for the way you intend to use your airplane.
Without elaborating here, may I recommend these two pieces
availble for viewing elsewhere?
<http://www.aeroelectric.com/altvreg.html>
<http://www.aeroelectric.com/bltinreg.html>
By the way, our weekend seminar schedule for 1998 is beginning
to shape up. See <http://www.seminars.html>
Bob . . .
AeroElectric Connection
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