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Message
Sport Aviation Feb.'96. There was a report about a
Canadian guy who ran a direct drive Subaru in a Dragonfly, turning the 54"-prop
at 3800 rpm for cruise and up to 4500 rpm for high speed, obviously the
tips are beyond mach 1.0 by then. However he reported excellent
performance. ( I think he called his plane "Xpresso").
If you can incorporate an electric or manual/mechanical
variable pitch system you should still be saving weight compared to a
redrive.
You might even get away without variable
pitch:
Also in Sport Aviation August '96 was a report
about the Davis DA-9 record plane. Though the pilot was/is one of the
smaller ones around and the Davis was custom built to his
size. The plane was powered by a C-90 with 90hp. It goes 260mph, but
take off is interesting as the prop is about stalled until 80 mph. The pilot
doesn't push full power until 125 mph, when the prop will really start to
bite. He starts the take-off roll with 2150 rpm and goes to 3150
rpm for a max speed run.
You might be able to use a way broader rpm range on your
slingshot/fan/rotary.
On the other hand if a variable pitch is necessary I could
shoot a couple of photos of our EC120 Tailrotor/Fan (or Fenestron as Eurocopter
calls it). The mechanics look rather simple, the fan blades are all loose on the
ground but tighten up when centrifugal force hits them. The fan runs around 4000
rpm, pitch is controlled via a Teleflex cable and has no boost whatsoever,
and doesn't need it.
The neat thing is you hardly hear it, in comparrison to a
regular Tailrotor it is silent. EC does this with irregular spacing of the
fanblades.
I suggest that a good balance job should be done, but I
don't see why this could not be used for an airplane. Diameter is about 2
1/2 feet.
You want detailed photos of the works inside the hub, let
me know!
I still need to find some references for unshrouded fan
design though.......
Any ideas or hints?
Thomas Jakits
PS: I am serious!! Sometimes my ideas may sound
outrageous, but I am not the smart inventor guy, I just remember when I saw a
neat thing and try to check up on it and let everyone know who wants to
listen.......
By the way, you should get a patent on your sound-proof
hat!
----- Original Message -----
Sent: Saturday, December 11, 2004 6:06
PM
Subject: [FlyRotary] Re: Serious single
rotor questions (serious??)
to build a direct drive fan. I have one that I ground tested
for 150 cycles at 6800 rpm with a tired 13B. It would be a snap to do a 100
mph fan. Mine's design point was for 250 mph with the inherent penalties as
low speed.
I can send you a picture if you're
interested.
Bernie
OK, hat's off, I'm
listening :-)
I'd love to see
pictures of what you're talking about. My uninformed understanding
of "fans" was that they were good for cruise speed, but not climb
thrust. I just never imagined one running on a 40-100 mph plane, which
is why I didn't take Thomas' post as seriously as maybe I should
have. Would it be lighter than a PSRU and prop? Would it even
fit on a SlingShot? I just have no concept of what you're proposing, but
I'm now mighty interested.
Thanks (to Thomas
too)
Rusty (weighing engine
parts, and planning cooler
locations)
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