Dan Duncan had gotten up past 13,000. He said he was balancing his
engines quite a bit tighter than the factory did it.
Dave Klingler
Consider the source :-)
The problem is not balance. It is centrifugal load on the rotor bearing.
That is why we run 150 psi oil pressure in the TTC engine.
Paul Lamar
What's the story about Dan Duncan and the doctor in Oklahoma ? Never
heard about it.
Steve Carlisle
I don't have all the details but I think he was convicted of mail fraud
and then
disappeared into Mexico I think. Many years ago.
Paul Lamar
Well I managed to find a 2009 Homebuiltairplanes thread relating to Dan
Duncan,
Re: Direct Drive Rotary?
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(
Warpdriveprops 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. WEIGHTS:
Basic engine with oil-pump, fuel-pump, water-pump, Posa 32 mm
Super-carby, ignition, engine mounts and prop-flange was 110 lbs.
To this must be added: alternator (4lbs), starter(5.5lbs), 9" x
14"engine coolant radiator(5 lbs), and 7" x 8" oil cooler(1.8lbs)
This gives a DRY INSTALLED WEIGHT of 126.3 lbs.
Engine-coolant( 10.4 lbs) and oil (6lbs) must be added...which brings
wet-weight up to about 143 lbs..... not bad for 60hp continuous with 3.5
gph fuel-burn(regular or unleaded) and a 3000 hr TBO.
How much static-thrust could be obtained from such an engine reving
at 4000rpm?
A McCulloch 72 HP ( 68 actual) two-stroke in a gyrocopter swinging a
48" or 50" diameter prop delivers about 260 lbs of thrust at around 4000
rpm.
Igor Bensen said that for "respectable performance" a gyro requires 1
lb of static-thrust for every 2 lbs of gross weight, so a 520 lb gross
gyro looks feasible. A small 4-stroke chain-saw engine(with a hand-pull
recoil-starter) could replace the heavy starter-motor, and could also
pre-spin the rotors. A smaller and lighter battery and alternator could
thus be used. Maybe EFI and a turbo would give more power (thrust), for
little nett additional weight. Duncan were also offering an "Aerodyne
Model 2.66 VATN turbo(Variable Area Turbine Nozzle)" , which weighed 15
lbs and which would increase power and quieten exhaust noise.
Duncan also offered a single-rotor fited with a Uniroyal HTD cogbelt
rated at 300hp. Reduction ratio was 3:1 and output was 120hp at 9,000rpm
for 5gph, and a DRY INSTALLED WEIGHT of 165 lbs. This power output
agrees with the output of a Racing Beat single-rotor bridge-ported
engine which NASA tested in 1982 which produced 128hp at 9000 rpm.
Does anyone else think a single-rotor direct-drive looks attractive
as a gyro-engine?
I can post a 3-view drawing of the engine if anyone's interested.
Steve Carlisle
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