Hello Paul, what can you tell us about this old company,
Duncan Aviation(Comanche, Okla.) many years ago listed in their brochure
a direct-drive single rotor Mazda RX-7 bridge-port aircraft engine. They
machined the crank to accept a new main-bearing located on the front of
the engine. The main-bearing was housed in an easily-machined circular
housing. Propeller-boss was attached to the front of the re-machined crank.
Engine was rev-limited to 60hp at 4000 rpm. Engine could be fitted with
a fixed-pitch prop, or cockpit-controlled variable-pitch prop( Warpdrive
props makes a carbon-fibre one, and their website has a good tip-speed
calculator). Duncan photo of this single-rotor engine shows it fitted
with a 2-blade in-flight adjustable prop.
Thanks,
Steve Carlisle
I got the impression he was a scam artist. Something about him moving to
Mexico
to avoid shipping product after accepting payment I think. Not sure.
Long time
ago. Perhaps he was just technically incompetent.
Technically speaking 4000 RPM is not very useful for a direct drive
aircraft engine.
The prop diameter needs to go way down to achieve 4000 RPM so the
prop is very inefficient.
Also a one rotor with cast iron end housing would be rather heavy for
only 60 HP.
A one rotor with cast iron end housing with 100 HP is rather heavy.
Especially when
one adds the gear box weight. The only reason people build bridge ports
is p-ports
are out lawed in certain SCCA class's. That makes bridge ports
irrelevant for aircraft use.
The only Mazda based one rotor that makes sense for aircraft use is a
p-ported all
aluminum one rotor with a gear box.
Paul Lamar
I knew Dan Duncan for several years, and one of my friends bought and
installed a 250HP turbocharged two-rotor engine from him. Dan rented an
apartment from my dad, and we spent quite a bit of time together. He
sold and built over 90 Mazda rotary aviation engines. To the best of my
knowledge there was only engine he ever sold that was not delivered,
although he refunded the deposit. That particular customer was a nightmare.
For a time he lived in New Mexico, which is one of 50 states in the
USA. Many people don’t know that, and I’ve lost track of the number of
people who’ve asked me whether I speak Spanish, and whether I drink the
water. We’re between Texas and Arizona. :)
Dan tried Mazda engines in dirt track racing in Oklahoma, liked them,
and started building them for his customers. He owned three airplanes,
and after a time he put an engine in his Tri-Pacer and decided he liked
that too. He and his wife started Duncan Aviation Engines, selling
about 80 engines from Oklahoma. They got a couple of contracts from NASA
to do research on aviation rotaries, and they did pretty well.
In the mid eighties New Mexico began offering grants, loans and tax
incentives to “high tech” companies if they’d move to our state. Dan and
his wife applied for the program and they were approved. They shut down
their business in 1986 and moved to Santa Fe, only to find that our new
governor had shut down all said loans and incentives. Dan and his wife
rented a trailer and she took a job to try to pay for the parts for
three engine orders they hadn’t delivered. Dan built engines and took
truck driving jobs.
Duncan Aviation had sold an engine to a doctor in Oklahoma about the
time they moved the company. He wrote a letter to the man to tell him
the engine would be delayed. The doctor wrote an angry letter back. Dan
wrote him another letter, asking him whether he’d like his deposit back.
The doctor went to his friend, who happened to be the Oklahoma Attorney
General running for reelection. The AG went on TV and made a speech
about prosecuting the “Dan Duncans of this world”, and presto, Dan was
famous. Dan and his wife were awakened one morning by the FBI, who went
through their files and charged Dan with around 180 counts of mail
fraud. Dan was shipped back to Oklahoma, where he was beaten up pretty
badly by the jail guards, causing a nasty hernia, which went untreated
for several years. He gave his savings to a lawyer who promptly took his
money and actually did disappear to parts unknown.
Dan ended up doing three years in prison for three counts of mail fraud,
the three letters that had gone back and forth between him and the
doctor. While he was in prison, his wife’s best friend convinced her to
divorce him. I ended up with his border collie, and without a lawyer he
was stuck.
When he got out, he moved into our apartment. He built a few more
engines and eventually won his wife back, but the injuries he’d gotten
in prison had really taken a toll on him. He worked as a commercial
truck driver and eventually moved up to Canada, where his wife was from.
The mail fraud charges made him a permanent felon, and he couldn’t get
loans to restart his business.
Dan basically offered four engines, a little Israeli rotary, a Mazda
single rotor, a 180HP dual rotor, and a 250 HP turbo. Cruise RPM was
about 7400, with a max at 9000, if I remember correctly. He used a
2.71:1 dual-Gates belt drive reduction based on his experience with dirt
track race engines. My friend and I put one of his engines on a Glass
Goose amphibious bush plane, and it was excellent.
Dave Klingler
Thanks Dave good information. I'll file this for the next person that asks.
Paul Lamar
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