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Group,
I appreciate all the different opinions and perspectives about this subject............Each of us as
experimenters has to decide for themselves their comfortable risk level...........I currently have a
Mazda alternator modified as described on my Chevrolet V6 powered 1988 RX7 with about
60,000 miles on the conversion (My 13B lost compression <apex seal> and I feel Rotarys are
wasted in cars so will now power my Dyke Delta)...............The internal regulator failed but
failed open instead of an internal short which would have allowed runaway voltage.........I do
realize that the majority of failures fail open , "But" my personal risk level still wanted the ability
to switch off field voltage and shut the alternator down in my "Delta"...........I do not currently
have a switch in the field circuit of my RX7 but will be installing one to test this as there has
been some discussion that residual magnetism in the fields might prevent the alternator from
shuting down............Will report my findings...........
I realize that abilities among experimental aircraft builders vary but in my opinion if you
can build a safe and flyable aircraft with a Mazda Rotary engine then the skills needed to
modify a Mazda alternator should be no problem...........This is not rocket science , all you
are doing is removing an internal regulator (I think the entire circuitry should be removed as
I previously stated) the brushes connected to ground and the field windings connected to
a now unused external connector..........Until the advent of the internal regulator alternators
were all built this way electrically.............IMHO & FWIW
--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold
-------------- Original message from "Mike Wills" <rv-4mike@cox.net>: --------------
> Charlie,
>
> Thanks for this perspective on the risk/benefit ratio of this particular
> mod. I too fly with an unmodified 1 wire alternator. Or at least I would if
> I were currently flying.
>
> Our airplanes are complicated enough what with EFI, EI, microprocessors,
> etc., without adding to the complexity (and potential failure modes) by
> adding "protection" to guard against 1 in a million failures. At least thats
> my perspective.
>
> Mike Wills
> RV-4 N144MW
>
> ----- Original Message -----
> From: "Charlie England"
> Subject: [FlyRotary] Re: Overvoltage ? [FlyRotary] Re: Modify Alternator for
> External Regulator
>
> > If you have a controllable circuit breaker or a switchable relay in series
> > with the B-lead, you can control an over-voltage event. The Aeroelectric
> > connection offered a 'crowbar' type protector for a while that would
> > disconnect the B-lead automatically, and if memory serves, Bob Nuckolls
> > now says that with an effective attention-getter to notify of
> > over-voltage, the battery will easily damp the voltage to below
> > damage-causing levels long enough to hit the B-lead disconnect. The only
> > issue left is whether there is enough combustible material in the
> > alternator itself to cause any real danger as it runs away, electrically
> > isolated from the rest of the plane.
> >
> > My personal opinion is that each person should carefully evaluate the
> > relative risks of opening & modifying an inherently extremely reliable
> > device, at their personal skill level. I spent about half my working life
> > doing electronics service work and I'm pretty confident in my abilities in
> > this area. My flying RV-4 (Lyc) has an unmodified '1-wire' alternator.
> >
> > Charlie
> >
> > Ed Anderson wrote:
> >>
> >> Just curious, Todd. When you had your alternator run-a-way, did you have
> >> a battery or other load on the line. Yes and you are correct, just
> >> because the odds are 1 in 1000,000 does not mean your 1 couldn’t come up
> >> tomorrow. And I STILL DON”T use approved plastic fuel cans (or any other
> >> kind) – one refueling fire was enough {:>).
> >>
> >> Thanks for providing that info to the list – now others can see
> >> alternator over voltage is a possibility with a car alternator and
> >> without the modification to the field coil circuit may be impossible to
> >> shut down – short of shutting down your engine.
> >>
> >> But, if 60 years of experience is not worth anything regarding
> >> alternators – then what is experience worth regarding anything. Like just
> >> about everything else in this “hobby”, you are constantly assessing risk
> >> (or should be) and I decided the risk of modifying my alternator to
> >> eliminate the remote risk (base on my experience) of over voltage was
> >> higher than an over voltage condition. YMMV {:>)
> >>
> >> Ed.
> >> *On Behalf Of *Todd Bartrim
> >> *Sent:* Sunday, July 05, 2009 3:07 AM
> >> *Subject:* [FlyRotary] Re: Modify Alternator for External Regulator
> >>
> >> Yeah, that's what I said too Ed, then it happened to me when I was still
> >> early in my flight test (on the ground fortunatly).
> >> However after years of carelessly pouring regular old auto fuel from
> >> plastic fuel cans, despite all the warnings, I've yet to have a problem.
> >> But I did hear of a guy that caught his plane on fire this way. ;)
> >> So yeah, I'm sure it could happen. Hope it doesn't though. It would sure
> >> ruin my day.
> >>
> >> Could it happen, undoubtedly, however, in 60 + years of driving
> >> automobiles, I have never, never had an alternator run wild – the ones
> >> that failed, just died. So if I can get by another 60 years {:>), then I’ll
> >> probably hang up my wings (or who knows perhaps get another pair {:>)
> >>
> >> Ed
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