> This is stunning in it's simplicity.
> since I am using the proven Ford A4OD six pinion planetary in a
> differential
> mode the total gear reduction is 6.34:1. The ring gear is rotating
> in one direction and the planet carrier is rotating in the other.
> As long as both props have the same drag the RPM's of each prop
> will be equal. With an engine RPM of 8500 the rotors will
> be turning 1340 RPM. We can probably use a 13 to 14 foot diameter
> rotor at this RPM. The red line on the RX8 engine is 9000
> RPM and a P-port RX8 engine will be making close to 300 HP
> or more at 8500 RPM. We will find out in a few weeks
> as I am building such an engine as we speak
>
> The over all diameter of this gear box is only
> about 6.5 to 7 inches. It will have it's own oil
> supply as it is on the very front of the airplane and
> the engine is at the very rear for weight and balance reasons.
> There is a stock RX8 carbon fiber drive shaft connecting the two.
>
> The first 3D is with gear box housing.
> The second is without gear box housing.
> The third is with the aft prop shaft.
> The gimbal is centered on the U joint which is a requirement.
> The gimbal allows the props to be pointed in any direction with in
> limits. The same as the Air Scooter. This will allow maneuvering in
> landing
> and take off mode and help with the transition to horizontal
> flight and back to vertical flight.
>
> Did we luck out or what?
>
> Paul Lamar ...No rotor no motor.
>
>
> Paul,
> Interesting idea. In theory it should work, But on initial startup, both
> rotors could turn the same direction. you will need to build a test
> rig and
> test the theory. Not being a forced synchronization, it may be yaw
> unstable
> in hover.
> Larry
>
> Yes that is true. I hadn't thought of that. Thanks for thinking of that
> Larry.
> Let me put my thinking cap on and see if I can come up with solutions
> to these problems.
>
> Once they are rotating the highest speed rotor tips will run into a
> transonic
> brick wall transferring the torque that is left to the slower rotor.
> If we
> make the rotors variable pitch the yaw forces in vertical mode can be
> controlled changing the rotor blade pitch individually.
>
> Here is a chart of drag coefficients of an airfoil as a function
> of angle of attack as it approaches the speed of sound. Small changes
> in pitch make large changes in tip drag.
>
> Also one rotor can be feathered on start up to insure they rotate
> in opposite directions. However one blade would be going backwards
> so that might be sufficient torque load difference so the unit goes into
> counter rotating mode.
>
> BTW I am thinking of using an infra red or laser link and slip rings for
> power to control the pitch on the front rotor electrically. Solves a
> lot of
> mechanical problems and saves a bunch of monkey motion pitch changing
> parts. It could also be be done super imposing low level pulse width
> modulation on the 12 volt power slip ring circuit. The power slip ring
> would have to be located in the gear box working on the back side
> of the planet carrier. This trick works on fuel pumps embed in
> gasoline.
>
> In that case
> a stock high torque model airplane servo can be used to change
> the pitch. The Kaman used an aerodynamic flap on the back of the
> blade to change pitch.
>
>
http://www.b-domke.de/AviationImages/Rotorhead.html
> "Kaman H-43 Huskie
>
> Two-blade contra-rotating intermeshing twin-rotor with servo-flap
> control.
> Rotor blades are attached to hub by drag hinges only, the servo-flaps
> eliminating blade pitch change and associated bearings. Movement
> of servo-flaps twists the blades with the natural resilience
> of the blades used to obtain torsional deflection."
>
> I don't like twisting the blades because IMHO it does not lead to
> the optimum pitch distribution along the length of the blade.
> I could be wrong about this as helicopter blades are not very
> torsional stiff to begin with and they may have a mind of their
> own when it comes to local pitch. Kaman may be on to something
> in this regard. Kaman's do have a reputation of generating a lot of
> lift however so some of that could be due to no tail rotor
> sucking engine power.
>
> I would rather use a torsionally stiff carbon fiber blade
> rotating around a bearing in the hub. The aerodynamic servo flap
> can still be used to control pitch.
>
> Since we will not be flying forward in helicopter mode for long the
> leading and lagging hinges can be done away with. Same goes
> for the flapping hinges. I think we can use GRP for the
> hub. Same as several European helicopters use. GRP has high
> tensile strength and a low modulus of elasticity allowing it
> to flex without failing. Same as the Long EZ main landing gear.
>
> Paul Lamar ...No rotor no motor.
>
>
> This is correct that the servo tab on the Huskie (and the K-Max)
> twist the
> blade and the lift distribution is not what you might like. I think
> they
> cheat a bit with the twist of the blade so that when the aircraft is
> hovering at gross weight, the entire blade is at optimum angle. The
> Seasprite has a very stiff blade while the portion of the spar that
> connects
> the blade to the rotor head has a much lower modulus so it does the
> twisting, not the blade. That's why I want to get a close look at one.
> That Eurocopter has one of the best rotor heads available.
>
> Steve Brazil
>
> Thanks for the insight on that Steve.
>
> --------------------------------------------------
>
> Redesigned the rotor head as we no longer need cyclical pitch change.
> We will be using the vectored thrust trick of the Air Scooter.
> I changed it to simple mechanical pitch change. I increased the size
> of the aft
> shaft to the same size as the ring gear. Namely five inches. A
> simple butt weld
> is all we need. One of the results of this is the gear case now
> becomes a simple
> piece of thick wall aluminum tubing about six inches in diameter and
> eight or
> ten inches long. This also allowed increasing the diameter of the
> front shaft
> connected to the planet carrier to four inches. The front shaft needs
> a lot of
> torsional and bending stiffness as it is cantilevered a fair distance
> out of the gear box.
>
> I will probably use plain bearings, oil filter and an oil cooler with a
> dedicated high
> pressure stock Mazda 13B oil pump driven off the input shaft. The
> remaining problem would be high speed shaft seals.
>
> Next will be telescopic rotor blades to increase the speed range of the
> VTOL canard from zero to about 200 MPH.... to zero to 300 MPH.
> Might as well take full advantage of all that 300 HP.
>
> Paul Lamar ...No rotor no motor.
>
>
> Paul,
> I am a 6000 hr helicopter pilot.
> I am also a K-Max and Husky pilot, and have been on the Board of
> Directors at Kaman Aerospace for 14 years.
> The aero flap principle of the Kaman rotor-system is brilliant and
> trouble free. I would heartily endorse its incorporation. What's
> more, most of the original design team is still around for
> consultation, if you would like to speak to the horse, as it were.
> Just say the word.
> -Reeves Callaway
>
> Wow! I didn't know that. Please send them some of this stuff and have
> them tell me what they think. I am sure they can come up with
> some serious advice and improvements.
>
> My goal here is to go faster than the Osprey which can go about
> 275 MPH. I think 300 MPH is within our grasp if this telescopic blade
> can be made to work. It will be molded in a closed mold preloaded
> with carbon fiber. One end of the mold will be subject to a vacuum and
> the other end will have epoxy resin injected at high pressure.
>
> There will be a left and right acme screw passing through the short
> part of the blade from end to end. One side will be a left hand thread
> and the other side will be a right hand thread. There will be an
> coaxial electric motor in the hub that turns the screw. The acme nuts
> will be located on the inner ends of the outer blade segments.
>
> The inner blades will have a slight twist so the untwisted outer
> portions can be retracted. Not ideal blade twist but it is a better
compromise
> than trying to run a large diameter rotor at high RPM in forward
> flight due to Mach limitations on the tip speeds.
>
> This scheme is designed to double the blade diameter for vertical
takeoff.
>
> Paul Lamar ...No rotor no motor.
"My goal here is to go faster than the Osprey which can go about 275
MPH. I think 300 MPH is within our grasp if this telescopic blade can be
made to work."
BUT
"Once they are rotating the highest speed rotor tips will run into a
transonic brick wall . . ."
SO,
in addition to extending the rotors for the most effective vertical
flight, you sweep the rotors for the most effective horizontal flight.
Like this photograph:
http://www2.nlr.nl/public/facilities/AVET-Info/Content/Pics/Prop_apian_isolated.jpg
"That's expensive!"
Extendable rotors are expensive, too. Since we are talking expensive,
we might as well keep on talking expensive.
But we are only talking, and talk is cheap. So, let's expend cheap talk
about the IDEA of swept rotors, the IDEA of cheating the transonic
brick wall and the DREAM of an efficient, VTOL, 400 mph aircraft . . . :-)
Les :-)
I am sure a prop blade planform like that would help under the right circumstance
but the tips still go transonic. It also does nothing for
helicopter like static thrust
Paul Lamar ...No rotor no motor.
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