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Old Feb 21, 2014, 05:06 PM
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Australia, NSW, Sydney
Joined Sep 2012
345 Posts
Idea
Collective pitch tailsitter

It ideas time again. While I've been too busy to actually do more with my other build, I've been thinking about the next one.

The idea is this:
Imagine a V22 osprey with full cyclic and collective pitch control, only without the tilt-rotor capability, no fuselage and no tail plane. The KK2.1 board would be placed on one side with signal wire connecting the two motor pods. Batteries would be place in each motor pod, with essentially nothing except ailerons in the wing section. I'll all vertical sections to the motor pods to act as landing gear, which will double as vertical-stabs.



Sounds dumb right?

Well consider the following advantages this design could hold for our application:

1. Less moving parts. No tail plane and no tilt mechanism means many less moving parts.

2. Lighter weight. The fact that there is no fuselage means there is no need for large power cables between the wing tips -- the batteries can be held right next to the motors. No fuselage or tail plane means the aircraft will be much lighter, while no tilt mechanism means the aircraft can be very strong while still being light.

3. Better aerodynamics. Less drag from no fuse or tailplane. More efficient in hover because air is moving over wing surface efficiently, unlike most tilt-rotors.

4. Faster than non-CP VTOLs. The variable pitch rotors allow for efficient hovering while allowing for efficient high-speed forward flight.

5. Extremely stable. Despite the lack of a tailplane, this design would be extremely stable in all modes of operation. The cyclic-pitch capability of the rotors means the pitch-axis of the aircraft is always stabilized, even in forward flight (no need for horizontal stab).

6. Easy (ish) to build. This design would be easier to build than a standard V22 style design because there is no tilt mechanism or fuselage. The main spar could be flexible without causing problems, unlike my tricopter-wing which requires extreme rigidity in the entire airframe to prevent problems. The weight distribution of this design (batteries near motors) also means the center wing surface can be very lightweight. Only small signal wires would be required to link the two motors.

Here is how I plan to build the rotors:
Using 450-size heli main rotors as a base design, I will attach folding prop blades to them with custom made alloy blade holders. The rotors will be around 10 inches in diameter depending on the final design requirements. Cyclic and collective pitch control will be achieved with only 2 servos (not the usual 3), since aileron cyclic in not necessary for this aircraft (instead, we use differential cyclic pitch)

Why I think I can pull this off:
I have built a very similar aircraft. A couple of years ago I built a "twinn rexx", a chinook made from two 450-size helis. It's a very similar concept mechanically, only with a beefy shaft connecting the two rotors so they don't collide. It flew well, but was plagued by mechanical problems caused by the sync-shaft. Essentially, there was about 4 hours of maintenance per 1 hour of flying. It was also very cool and intimidating at the same time, because the rotors were very loud from the blades hitting each others vortices.

This design however, does not require synchronization between the two rotors, so would not be haunted by those issues. Here are a few pics of the build:

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Old Feb 21, 2014, 05:58 PM
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v22chap's Avatar
United States, IN, Granger
Joined Jan 2003
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This has already been built .... Rotormast.com has a full scale ship or you can buy a profile V-22 .... all controls and batteries are on the nose section ....... I have hovered mine several times this way .... it also uses NO airplane controls to transition and fly in airplane mode ... it is all done with helicopter cyclic controls !!!! However I have not transitioned or flown in airplane mode with no tail surfaces ... I would think that to be impossible ,, but then again a flying wing flies with very little tail surfaces ....
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Old Feb 21, 2014, 06:17 PM
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Australia, NSW, Sydney
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Oh I'm very familiar with the rotormast v22. But that is not what I'm trying to build. I dont want a fuse or tail or tilt. In fact, what I'm trying to make is a collective pitch VTOL with as few moving parts as possible.
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Old Feb 21, 2014, 06:32 PM
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United States, IN, Granger
Joined Jan 2003
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That is what I am saying ... rotormast .... without conversion servos and the tail section is what you are talking about building ....
Quote:
with full cyclic and collective pitch control, only without the tilt-rotor capability, no fuselage and no tail plane
His onboard computer is already programed to fly it in tailsetter mode ... you don't need a KK board

But go ahead and reinvent the wheel if you feel the need
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Old Feb 21, 2014, 09:02 PM
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Australia, NSW, Sydney
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I never said I was breaking new ground with this idea.. Just want to make one is all

KK board is also a fraction of the cost of his.
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Old Feb 21, 2014, 09:05 PM
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.. That and I have almost all the parts I need right here. Why would I buy that when I have the stuff I need here?
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Old Feb 21, 2014, 11:57 PM
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Australia, NSW, Sydney
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Hey v22chap, I've had a little time to think about what you were saying, and I have to say I agree. Looking at the parts they have, I might even buy some to make the build process easier e.g. The blades
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Old Feb 22, 2014, 09:28 AM
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United States, IN, Granger
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Now you got it ... I was also thinking of his two servo cyclic control system too--- it gives you the control you need but using 2 less servos than the normal 3 servo ccpm ( less weight on the bird ) ..

His 3 bladed head system would be great for it also and then it would fit his twisted blades right and I would go with the twisted ones ...as without his controller ... I doubt you will ever do airplane flight with just regular heli blades(been there tried it many times ) His controller has an RPM governor monitor system that automatically monitors the motor rpm and will back off collective and then put it back in when conditions are meet ,, so as to maintain a certain RPM / wattage setting so you don't stall out the blades or lug the motors down ,,so that you get the most speed you can from just regular heli blades ( there is a reason his controller cost so much ... and it is because of all it does ) .

With the twisted ones he figures you get almost 20 % more performance as far as thrust and almost don't need the collective governor .The extra lb that the fuselage puts on his model is almost to much extra weight for the orginal flat heli blades to pull through into airplane flight .

You might also want to look at his manual ( free to download on his website ) and see how he distributes power to the servos that are on that far out of leads .... and use his
NWB (power / signal distribution ) boards to help with that ... it makes sure that you get power enough out there to run the servos with out making the rx brown out . It also makes for easier running of the servo signal wires as you only need one 3 wire extension for the two servos / throttle ,,, instead of one 3 wire servo lead for each servo and throttle control ( all less weight )
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Old Feb 24, 2014, 07:11 AM
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Newport News, Va
Joined Sep 2004
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jolyboy,
Boeing Vertol (Philly) in the 90's, built and flew a tailsitter with full collective and cyclic that looked a lot like your photoshoped V-22. The Boeing vehicle crashed during trials, the money dried up, the project abandoned. It's a very promising concept.
Gene
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