Marv, I hope this doesn't step on too many toes, but here goes:

Well, he did identify himself as having a financial stake in his statements.

Some of that stuff is probably true for *some* a/c alternators. Some of it is not universally true; some may not be true, period. Some alts have canted brushes, some have perpendicular brushes. Fan orientation will affect airflow to some degree, but thousands of auto alts. are being run successfully in a/c with no fan at all, using blast tubes. The ones with fans still attached still move air when spun the other way. Some car engines spin the alt in the same direction as a/c engines. Some a/c alts might have locking tabs, but not all. According to auto docs, some auto alts are wound delta & some are wound Y. He mentions that alts are birotational then later says that a/c alts are wound backward for backward rotation. He says that the rotor shaft is shorter but the cases are identical. While he's probably correct about special insulations, coatings, etc for turbo'd & turbine hardware designed for extreme altitudes, I strongly doubt that much if any of that applies for stuff found on NA piston singles. It doesn't seem to apply for some electric gear retract pumps, which are straight out of marine outdrive tilt mechanisms. I've witnessed certified a/c alternators work just fine after being rebuilt in greasy floored auto electric shops with auto components. Not on my airplane of course... If anyone needs something overhauled, bring it with you to the rotary spring fling thing & we'll run it 9 miles down the road to the uncertified repair station.

If there's interest, I'll post the article on the aeroelectric list & let Bob Nuckolls critique it.

Charlie
(feeling irritable after a day of figuring out how much it has cost me this past year to have my money spent where & in ways I don't want it spent)

Kelly Troyer wrote:

I do not know about everyone elses engines but my 13B turns the same
direction as A/C engines built in the US !! I do not know enough to
comment about the other differences noted.......
-- Kelly Troyer
Dyke Delta/13B/RD1C/EC2




    -------------- Original message from "Marvin Kaye"
    <marv@lancaironline.net>: --------------


    > I thought you'd find this interesting.
    >
    >
    >
    >
    > Posted by "Hamid A. Wasti" to the Lancair Mail List:
    >
    > I saw this posted on another list. I am passing it along for
    general
    > interest, with no warranty for the accuracy of the information
    contained in
    > it.
    >
    >
    > From Pifer's Airmotive, Inc. Pontiac MI
    >
    > DIFFERENCES BETWEEN AIRCRAFT & AUTO ALTERNATORS USING A FORD
    BELT DRIVEN 12v
    > OR 24v ALTERNATOR FOR A COMPARISON
    >
    > 1. Although alternators are bi-rotational, aircraft engines turn
    opposite of
    > automotive. This means cooling fans must be canted in the
    opposite direction.
    > Also, pulley and belt size vary due to coming-in speed.
    >
    > 2. The thru bolts are of a higher tensile strength utilizing an
    > anti-rotation
    > device in the form of a lock tab. The rectifier assembly has a
    heavy duty
    > diode with higher voltage and amp. capacity. Also, one excites
    at 90 PIV (Peak
    > Inverse Voltage) and the other at 150 PIV. Radio suppression is
    designed for
    > 108 frequencies and up which is the VHF and 108 and down which
    is FM band.
    >
    > 3. The brushes have a higher graphite content and they utilize a
    tin plate
    > on
    > the brush leads to prevent corrosion.
    >
    > 4. The stator is of the Delta wind rather than the “Y" wind and
    it does not
    > utilize the stator terminal. The aircraft unit also carries “H"
    insulation
    > which is capable of 200 degrees centigrade temperatures. It also
    is rated at
    > 60 amp. instead of 55.
    >

    > 5. The rotor has a shorter shaft and a smaller thread size.
    Because of the
    > opposite rotation it is wound in the opposite direction. It also
    uses "H”
    > insulation and Havel varnish.
    >
    > 6. The front and rear housings are the same as automotive.
    >
    > With this brief description, I hope I have enlightened you on the
    > differences
    > between aircraft and automotive alternators. Using automotive
    units in an
    > aircraft creates a potential safety hazard as well as a short
    alternator life
    > and unreliability.
    >
    >
    >
    >
    >
    >
    > >> Homepage: http://www.flyrotary.com/
    > >> Archive: http://lancaironline.net/lists/flyrotary/List.html

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