VTOL flying Droid - Does it work?

[Nurbs]

I recently saw this (old) thread (http://www.rcgroups.com/forums/showthread.php?t=31741&page=2&pp=15) where Choppa Nutta posted a rendered idea for a VTOL-aircraft.
- Has anyone build something similar?

I just had to make a 3D model myself!

My model is based on a 10" prop.
There are two moving surfaces. They are controlled by one servo each. In neutral position they are trimmed to counteract the prop torque.
When moving the elevator stick back, both rudders would move "back" and the thing would tilt and move "forward".
Turning is made with an elevon-mixer - by moving both rudders opposite to each other.

Now, the main concern is stability.
As far as I know - these are our friends:
1. low CG - pendulum stability
2. stabilising fins and rudders
3. gyroscopic stability
4. pilot input ;-)

I have limited experience with hovering.
- Would it be possible to maintain stability, without using gyros?

[Bill Mixon]

Thats a nice 3D image.
What did you create that with?

I think you need at least 4 moveable surfaces. The way it's drawn, you would have control over the roll axis or torque, and in one other direction. But nothing in the other direction. I wouldn't count on the pendulum effect to hold it straight. Procession will take effect when it moves and I think you really need the control on that axis.
There isn't much rotating mass so the gyroscopic stability will not be that great.
There have been some similar aircraft that did fly, but they used 4 moveable surfaces.

[Andy W]

I've seen models like this fly, in competitions where a model has to fly from one side of an area to another, picking up and dropping off small loads, all completely automated.

.. seen lots of crashes, too! :)
..a

[Sparky Paul]

Without a torque reactor, this thing will spin out of control as soon as the legs leave the ground.
Something -must- counter the propellor torque.

[Nurbs]

Thanks for the input!

If I made 4 movable rudders - I could get away with only 3 servos, right?
2 servos for the yellow rudders with elevon mixing (as shown) and a third servo that should turn the red and white rudders (together)?

Wow, that would be a challenge to control!

Shouldn't it be possible to eliminate the prop torque with the rudders, just like trimming elevons or ailerons to stop the rolling force?


I'm still not sure if it's worth a try, but I have started anyway to build the cylinder of depron. It should fit an 11x4.7 prop. I guess an 11x3.8 would be even better. The motor would be my little Nippy 0808/98 on a 2s Lipo.

I use 3DStudioMax6 btw...

[Andy W]

The ones I've seen have two props, top and bottom, rotating in opposite directions.
..a

[Bill Mixon]

If I made 4 movable rudders - I could get away with only 3 servos, right? 2 servos for the yellow rudders with elevon mixing (as shown) and a third servo that should turn the red and white rudders (together)?

Shouldn't it be possible to eliminate the prop torque with the rudders, just like trimming elevons or ailerons to stop the rolling force?


It may work, but it would require a lot of deflection of the surfaces, and if you only used two to counter torque even more deflection would be needed. With the surfaces deflected like this a lot of your control is lost, due to how asymmetric everything is.
This best way to get these to fly easily would be to use counter rotating props as Andy mentioned above. This evens out a lot more than just the torque, and really makes it more practical to fly.
Of course this is more complex and as far as I know there are no pusher or reverse rotation matching props in this range, so you might have to end up making your own. It seems like I remember a thread in the micro/indoor forum where someone was building an Osprey with counter rotating props of some make. I think they were a bit smaller though.
As to how easy these are to fly...
All that I have flown were harder to fly than a micro heli. They can be very unstable, and have unpredictable tendencies.

Bill

[Sparky Paul]

..
Shouldn't it be possible to eliminate the prop torque with the rudders, just like trimming elevons or ailerons to stop the rolling force?
...
.
I've seen an electric helicopter with a large vane at the end of the tail boom instead of a tail rotor.
It requires something like this, a large surface that develops a counter-force to the torque, in place of counter-rotating motors.

[Bill Mixon]

Nurbs,
Have you looked at the Hiller flying platform.
It's an interesting VTOL, and is worth reading up on. I saw a video of it several years ago with the pilot shooting a rifle from it while up in the air. Looked to be very stable, despite everything being above the props. Sometimes stability doesn't work like you might think.

Hiller flying platform (http://www.hiller.org/exhibits/online-exhibits/flying-platform/flying-platform.html)

[hover dude]

here

[hover dude]

that was a mistake is the post earlier. there are some contra rotating props on this page toddsmodels (http://www.toddsmodels.com/propellers.htm) they are 10*4.5 props

[Nurbs]

I will look into counter rotating props. They would make it more complicated than I have hoped for - but I guess I used too many shortcuts on the 3D-model.

Good to know that you can get such props.

[gouch]

I use 3DStudioMax6 btw...

I'm guessing this is where you got your user name?

Good luck with your project, I have no input to it, I just like the look of it :D

Cheers
Paul

[Mr.RC-CAM]

I will look into counter rotating props.
An excellent example of counter-rotating blades can be seen by looking at the Hirobo Lama XRB model helicopter. It is VERY stable and does not have a tail rotor (well it has one, but is decorative only).

RC-CAM

[Miderror]

This was old school
about '95
Flew ok
Tethered power

Good luck

[Bill Mixon]

Miderror,
Is that you, Miller? Sent you a PM.

[hall woo]

Use a pendulum like THATOVALGUY who flew the BORG Cube

[Salto]

Interesting project Nurbs, and wonderful graphics!

I happen to be working on something similar myself, and will hopefully test fly it this weekend. If you don't mind me using your thread I'll post pics and a flying report here next week.

But in the mean time I have some comments on the stability of such machines. I've thought some of these issues through pretty hard over the last few weeks, but I do stand to be corrected if I've got things wrong.



Now, the main concern is stability.
As far as I know - these are our friends:
1. low CG - pendulum stability
2. stabilising fins and rudders
3. gyroscopic stability
4. pilot input ;-)


1. I don't think a low C/G contributes to stability at all, in fact I think under some flight conditions it may even create a de-stabilising moment.

Let me explain my thinking. If the model is not translating (moving in a horizontal plane), the thrust force always acts along the centre line of the model. Air will be sucked into the prop, as well as expelled below the prop, directly along this centre line. If the C/G is also on this centre line (which I assume it is) when not translating there is therefore no stabilising or destabilising moment created. So it will be neither stable nor unstable in untranslating flight.

If the model now tilts, there will be a component of the thrust acting laterally (relative to the ground) so the model will accellerate laterally (and loose altitude if power is not increased). This is where my thinking gets a little hazy, and please correct me if I've got it wrong, but I think this sideways force acts at the prop, which is above the C/G of the model, so a destabilising moment is set up. Think of the weight of the batteries etc. hanging below the prop acting as a pendulum which will lag behind any sideways movement of the prop. This lagging tilts the model further in the direction of the movement, which increases the accelleration, ie. the system is unstable. For stability, you would actually want the vertical C/G to be above the prop.

Things get even more complicated as the model starts to translate (relative to the surrounding air mass). In this condition, air will no longer be sucked into the prop along the model centre line. The incoming air vector tilts towards the direction of movement. Now one side of the propellor (the retreating side) will be seeing a higher angle of attack than the opposite side which will produce a torque tending to tip the model over. Precession will move the model around an axis perpendicular to this applied torque. Depending on the direction of prop rotation this resulting movement may either be stabilising or de-stabilising.

The holes in my arguments (if any!) will be in my assumptions of where the sideways force acts (at the prop, or at some other location), and whether the precessional torque is indeed reversed with reversing prop rotation direction. My physics is a little rusty here.

2. Your fins and rudders as drawn will not contribute to stability, only to the pilots ability to keep the model pointing and going where he wants. If they were above the C/G they would be stabilising. The main attribute of your design contributing to stability is the high mounted prop shroud.

3. Gyroscopic forces won't necessarily keep the model stable. But they will dampen any movements.

4. If the pilot was me, then pilot inputs would definitely be de-stabilising!

Any comments?

Graham.

[Bill Mixon]

Graham,
Did you see the Hiller flying platform that I posted a link to? This stability issue is something that I have never been able to figure out. There are so many things going on that it's hard to understand how one element will effect the other.

[Salto]

Bill,

No, I missed your reference earlier. But having read it now, I'm more confident in my arguments above.

There are two distinct effects here. 1, The sideways thrust force resulting from a tilted prop disc, where precession doesn't enter into things. And 2, the leading/lagging prop issue, where presession does effect things.

I hope someone can clarify my thoughts on the precession issue, and confirm whether the prop rotation direction flips the system from stable to un-stable.

Graham.

[Nurbs]

Very interesting Graham! I'm looking forward to see your project! Please post!

I've been busy with other projects.
I built the prop shroud - that's it :-)

You got me thinking... Where would the "centre of rotation" be on this thing?
If you look at it as a pendulum - where is the "suspension" point?
I have imagined that this model would "dangle" around the prop disc. Is that correct? Or would it rotate at the CG-level?



Think of the weight of the batteries etc. hanging below the prop acting as a pendulum which will lag behind any sideways movement of the prop. This lagging tilts the model further in the direction of the movement, which increases the accelleration, ie. the system is unstable. For stability, you would actually want the vertical C/G to be above the prop.


OK, I thought.... More lag ==> greater angle ==> longer moment arm ==> greater self-correctional pendulum force ?
A pendelum with a very LOW CG is considered stable, right?



3. Gyroscopic forces won't necessarily keep the model stable. But they will dampen any movements.


I agree. It won't give you any self correction.



4. If the pilot was me, then pilot inputs would definitely be de-stabilising!


That would include me too :-)

[Salto]

I built this primarily to see how a model would fly with massive amounts of sideways "lift" available. It was designed to fly 3D stuff outdoors, but in hovering mode it is kind of like the design posted by Nurbs.

I flew it briefly this morning before the wind got up, and all I can say is that flat turns are VERY impressive!! It's surprisingly easy to fly and well mannered as long as you remember to go easy on the rudder.

Things get complicated fast because visual orientation is weird, and the model responds very fast in all axes. Flying towards yourself at high speed, then hitting full rudder for a fast flat turn at head height looks pretty spectacular!

It pulls up into a hover just like a conventional 3D plane, and as you would expect control in the hover is strong. I need more time to tweak the C/G, control throws and stuff before I can make any comment on whether it is stable in a hover or not. Hopefully tomorrow it will be calm enough for another flight.

Oh, the title of this post is a resullt of my 7 year old daughter asking me to please explain what the hell I was making. I answered "an X plane" - and the name kind of stuck.

Graham.

[Salto]

If my brain was up to it, I would program my TX to fly it like this. But for now it just has four aileron servos in parallel on one channel, and one each on rudder and elevator, so I fly it with one wing horizontal and one vertical.

Having an extra dimension in which you can do high G turns opens up a whole new range of aerobatic maneouvres. Can I call it a 4D plane??

[Salto]

The hollow EPP wings are made from rejected cores from my "Toccata 3D" design. More details here http://www.rcgroups.com/forums/showthread.php?t=275295&page=1&pp=15

The tail boom is an 8mm CF tube. Power is from an AXI 2212/34 on Tanic 3S 850 cells. Flying weight was 360 grams before I painted it, and 420 with the flouro paint job - DAMM!!! Some lessons I'll just never learn.

Tail feathers are two 3mm EPP sheets laminated over a 3mm spacer. Stiff enough for flying, but bendable enough for tail first landings.

[Salto]

If you think it looks strange here, you should see it in the air. I can't wait to give it full aileron travel!

[Magnum9]

This has to be the Toccata 4D straight from the Twilight Zone!!!

Would v-tail mixing not enable it to fly the way you suggested?

P.S. With all the stuff you keep coming up with, do you ever actually do any "real" work? :p

[Salto]

Magnum9,

You're right! All I need to do is V tail mixing on the two existing tail servos. I'll have to give it a go. But I probably should change the colour scheme before I try that.

Ah yes, Toccata 4D it is.

And yes, I usually put in about 50 hours a week "up at mill". I manufacture electric scooters for elderly people there.

Graham.

[Purdue Aero Man]

Video!!!!

[Nurbs]

Graham, that's a cool looking aircraft!
I would love to see a video.

Can it be easily trimmed to counteract the prop torque? I mean, can you maintain a direction when travelling horizontally?

Do you manage to land it vertically on the tail?

Keep us updated!

[Salto]

I'll try and organise a video.

Nurbs,
Prop torque is just not an issue. The four big wing panels damp any movement in roll very effectively, and the four ailerons have massive authority. Even at zero airspeed (hover) if it starts spinning it just needs a touch of aileron to check the movement. Like all hovering models, things only get difficult when descending with significant backwards airspeed. Here, the outer portions of the ailerons start to produce a reversed roll torque, so roll control gets unpredictable.

Yesterday I flew 3 more packs on it with the C/G close to the neutral point. In forward unstalled flight it flies pretty much like a conventional plane. The pitch response is a little slower due to the high moment of inertia around the pitch axis (that second wing), but not as bad as I expected. It will still do quite tight waterfalls. Knife edge is a no-brainer, as are flat turns.

With +/- 30 deg. aileron travel it rolls fast, and the roll damping seems stronger than a conventional design, ie. it stops rolling instantly when the aileron stick is returned to centre.

Vertical take offs are easy, and with a little more practice I should be able to land it on its tail. This will be useful, as it sure doesn't like landing conventionally!! At the moment I just harrier it in and drop it on the tail feathers. To quote Oldpilot "Where would you be, without EPP".

It has some interesting flight characteristics that conventional layouts don't have:
As it rolls, one or both wings continue to lift all the way round the roll, so you don't need to move the elevator or rudder to keep it on a horizontal flight path. It will do slow, 20 sec. rolls and just keep flying straight and level. Looks weird!

With the current elevator travel of +/- 35 deg. it won't spin or snap or drop a wing. It is much more stable doing slow harriers than it's single wing cousin. I haven't flown it yet with the C/G behind the neutral point, maybe it will spin then.

But the biggest difference to a conventional layout is the behaviour in a hover. It is spectacularly controllable. It is so easy to hold vertical, and so easy to stop it rolling. I would even say it is more stable than a model helicopter. If it starts to fall off vertical everything seems to happen real slow, so you have more time to react and get the right correction applied, and with the perpendicularly symmetrical layout the required rudder/elevator corrections are identical to each other which makes it easier to predict the right amount of correction.

The key finding, and the answer to Nurbs' original question is that it is not actually stable in a hover, just extremely easy to control. I need to do more experimenting with the C/G to find if I can get it stable, but for reasons I posted earlier I suspect the only way to achieve this would be with a pusher layout.

Graham.

[raptor22]

Awesome. I think I've gotta make something like this!

--Alex

[Nurbs]

More questions on this interesting model...

You have ailerons on both wings, right? (4 ailerons)
What if you'd use ailerons on only one of the wings (2 ailerons to keep the number of servos down)? Would you loose any control, you think?

How do you control the tail rudders? Do they work just as a conventional rudder and elevator, or do you use any special mixing?


But... I'm having a hard time getting used to the idea that a high-CG vertical "pusher" would be more stable than a low-CG vertical dragger.

If you were trying to balance a pen on top of your finger (pusher) - the pen would lag behind the movement of your finger, right. And I would say that this angle would create instability and gravity would tilt the pen even further. Or am I missing something here?

[Salto]

Nurbs,

It's got four servos, one on each aileron. I used 4.5g servos to keep the weight down. To save weight further you could use one servo for each wing (mounted near the centre and driving two ailerons at their roots), but you'd need larger servos so the weight saving would be minimal. I also prefer to drive the ailerons directly with servos near their centre - this gives sharper control.

Because I wanted this model to respond like a 3D model I used four ailerons. If all you wanted to do was hover then I think two ailerons would be OK.

The tail feathers are like two all-flying stabilisers. The elevator stick controls one, and the rudder stick controls the other. There are no mixes on the TX, just heaps of expo on all three control axes.

I don't think the pencil analogy is the best way to think of how these models fly. With my model's configration, when it tilts the thrust still acts directly along it's centre line (unlike on the pencil in your example), and the weight acts at the C/G, so there is no stabilising or de-stabilising moment set up.

It's only when the model starts to translate (move sideways) that stabilising or de-stabilising moments start to happen. As far as I can see, these moments are produced and infuenced by three effects; 1. the position of the C/G relative to the side areas of the wings and tails, 2. precession effects, and 3. differing angles of attack of the prop blades on each side of the prop disc causing torques perpendicular to the prop rotation axis.

If I've got it right, the layout that makes all these moments acting to stabilise the model is a pusher with a very low C/G.

I've got to go to work now, but if you want me to explain further please ask.

Graham.

[mlbco]

Graham,

I like your model, it's probably the best compromise for hovering and 3-D flying.

The pictures below show my latest project which is work-related. It is an electric RC prototype for a VTOL UAV that will eventually be gas powered. The model shown here is 5 ft long, 4 ft span and has 8 moveable vanes behind the propellor inside the duct. There is a custom mixing board to move the vanes for roll,pitch,and yaw. I installed 3 heading hold gyros to make it easy to hover (it is!). It's a bit overweight at 6.2 lbs and has limited excess thrust. I can hover and transition it, but I must be careful to descend very slowly when hovering or I won't have enough power to climb.

I chose a pusher layout to leave the nose area free for a gimbal camera system that will be part of the UAV version. The prop is ducted because the military prefers this to exposed blades.


Steve Morris

[Salto]

Steve,

Nice work, I like it. You must have the best job in the world!

Does it hover without the gyros? Is the pusher configuration stable in the hover without the gyros? Can you make any further observations about it's behaviour?

How do you transition from hover to forward flight, at what point do you switch off the gyros?

My next build was going to be like this, but with the X wing. I'll post my results here.

Graham.

[mlbco]

Graham,

I'm not skilled enough to try hovering it without the gyros. I'm not a 3-D capable pilot and don't know how to hover an airplane, so I can't offer much info on this. It feels like a stable helicopter with the gyros on.

The biggest problem with this configuration is aft CG and high inertia. The duct, vanes and motor are all at the back and this forces the batteries to be far forward, hence the long fuselage. The inertia in pitch/yaw is very high with all this weight at either end, and large inertia is not good for 3-D flying. You can see from the wing position that the CG still isn't that far ahead of the vanes (compared to the fuselage length) and the pitch/yaw torque is probably not as effective as in your configuration.

The close-coupled controls also results in "non-minimum phase" control response. This means that when you attempt to tilt the vehicle (in hover) the initial effect of the vane deflection is to produce a force that pulls the vehicle opposite the direction you really want it to go. If the CG were far enough ahead of the vanes this problem would be minimized, but it is noticeable when trying to make precise corrections in hover.

I transition to forward flight by climbing and tilting forward simultaneously. You can leave the gyros turned on in forward flight, but the control response will feel strange. I turn them off as soon as I begin transitioning. I have hovered in 15-20 mph winds with the gyros on, although this type of flying is in the transition regime and not really hovering.

Thanks,

Steve

[mc71]

Thats really cool Graham. I'll see you tomorrow night.

Matt

[Gizzmo0411]

I had posted a thread about a design similar to this a while ago, I was wondering if anyone had tried it. I've gotta see a video for this...Please try and post one, I'm real curious about the difficulties it might propose while flying...Landing, visual problems, etc...It's just a damn cool project man...:-)

[Salto]

Gizzmo.

I promise I will organise a video as soon as time allows.

It sure is interesting to fly. In many ways you can just fly it around like a normal plane, but it also has some wildly different characteristics. The fact that it continues to lift all the way around a roll is very strange. It's also super stable in a harrier, and when entering hover, I think because the top and bottom wings are like huge stabilising surfaces, actively opposing any tendency to drop a wing.

I flew it indoors last week in a smallish hall. Usually, flying a heavier outdoor model in here is a real handfull, but this thing slows up so well it was a doddle to fly around at slow speed in and out of hovering flight. It hovers so well, it's not actually stable, as in you can't leave the controlls alone, but is so vastly different to any conventional layout model I've flown that it just seems to sit there. It also retains strong aileron control in a hover, and also maintains this control as it leaves the hover. I've noticed when a conventional model leaves the hover there is a period of time as the flying speed hasn't yet built up when aileron response is not good. But the X wing just has rock solid response all the time in any attitude or flight speed.

To try and answer your specific questions.
As long as you keep in your mind which way it's oriented it's relatively straightforward to fly. The blue underneath and flouro red on top colour scheme helps here.

It has normal responses in roll and pitch, but you do have to be careful on the rudder. It is quite capable of doing a horizontal waterfall, which will have it pointing in another direction very quickly. It does horizontal flat turns, etc. faster than it does maneouvres in pitch, I guess because the vertical wings can use all their lift for changing direction, whereas the horizontal wing has to also oppose gravity.

Conventional landings are not on. I've hit the lower wing a few times, which results in a very rapid downwards rotation into terra firma!! Although the other night indoors, I was able to scrape the lower wing tip along the smooth floor a couple of times. So, landings have to be a catch, or better still landing vertically on the tail - something which I'm yet to master.

The difficulty with landings is probably the only limitation of this layout. Being made from EPP, and designed to deflect rather than break, makes this a non issue though.

Graham.

[mc71]

It was a blast to fly the toccata 4D (is that we are calling it now?) It really is as easy to hover as a helicopter. I want to have a go with it outside. I have a few short crappy videos from my digital camera.

Orientation was very interesting especially because I know I respond more to shapes not colours, I only flew it conventionally once or twice because I dont like destroying grahams airplanes when they are new but the hover and torque rolls were great.

Leanne thinks it looks like a killer whale when it is flying around because of its big fin sticking out of its back, and after you ate up Grants tocatta which looks like a fish it sort of had a new meaning.

Matt

[angrykoala]

So the Toccata 3D has survived a week of abuse while on our
Ozzie beach camping holiday (http://www.rcgroups.com/forums/showthread.php?p=2769915) .

Flew it several times each day in a confined camping area. Tree kept snatching the Toccata 3D.

So after a full week of abuse, with nothing needing more than a bit of glue to fix, my 3D gets eaten by the 4D at the indoor meet. :eek:

-Grant

[Salto]

I wanted to test the theory that a pusher should be more stable that a tractor for this sort of hovering device. So I built this:

[Salto]

It has an AXI 2204/54 mounted at the trailing edge, and elevons and rudder on the large tail directly in the prop wash. With only elevons (not 4 ailerons like the first model) it still has adequate roll control, and with power on, pitch and yaw response are strong.

With a forward C/G (near the neutral point) it flies just like the first one, but is not any more stable in a hover. With the C/G back at the trailing edge of the wing it will take off vertically from the ground into a hover and hold there reasonably well, but is still nowhere near hands-off stable. But as soon as it moves one way or the other at more than a crawl, it becomes impossible to hold in the hover. If I try froward flight with this rearward C/G it is completely uncontrollable. It balloons violently, and won't stay pointing in any direction - even straight up. This is pretty much as you'd expect.

I'll try some more C/G tweaking, but so far my conclusion is that this configuration is no more stable than the first.

Graham.

Here's a pic of the control surfaces.

[gouch]

Graham, you keep coming up with the most amazing air craft!

Cheers
Paul

[y.takahashi]

Hi! Nurbs san -- :)
although I am also studying VTOL, it has not succeeded yet As long as your CG picture is seen, the way which used the gyroscope thinks that the rate of a success becomes high. By reflection of man, there is speed which cannot catch up in the measure against anti-torque, and attitude control especially. The way which used the propeller of double reversal ideally thinks that it can cope with it efficiently to anti-torque. When making it correspond to the measure against anti-torque by four rudders in the case of a single propeller, for the reason, a thrust is taken and floatage becomes unstable. When it and the body incline, a mixing circuit with 2 gyroscope of the pitch axis which controls surface, and a roll axis is required for the opposite direction of that. It becomes using those gyroscopes and a complicated system is needed.

[BoonAIR]

need to ask smt abt UAV.

Is there other way to oppose the torque reaction by the main rotor other than the use of tail rotor?

Can we us efins to oppose the torque reaction?

[Sean Kinkade]

I just started an electric RC flying platform project. My goal is to make affordable and easy to fly ARF flying platforms, saucers, and droids.

I hope to pull this off and have my first kit on the RC market soon, hopefully before Christmas. The price of micro piezo gyros has come down enough now to make this feasible.

I grew up with Jonny Quest so I am trying to model after the flying platforms and hovercraft from the cartoon series. The cartoon series based much of the V-TOL craft on actual machines of the late 50's, early 60's but greatly simplified their appearance, which will be a great task to duplicate in an RC model. The key is obtaining stability without unsightly external vanes.

This has been done with the small co-ax helis and with the 4 bladed "Roswell flyer" type of craft, but my first design is a flying barrel basically, with two contra rotating props contained within( Hiller flying platform style) and with two figures standing in it. I have the thrust already....boy do I have the thrust! The only thing left is the control system. I'll be trying a dynamic control system that I think will work. I should know whether the concept works sometime this month ( June 2005) and I'll post my findings, hopefully with video.

Sean Kinkade
HobbyTechnik

[Sean Kinkade]

Here are some photos of what I'm aiming to duplicate the best I can....

Sean Kinkade
HobbyTechnik

[mlbco]

Sean,

I've worked on several "barrel" type UAVs (I liked to call them flying toilets..) and here are some observations:

1) The distance between the vanes and the CG is very important for pitch and roll control. If the vehicle ends up being squashed flat like a flying saucer then there is very little torque generated by the vanes, except about the prop shaft (yaw) axis. If the CG is too far above the vanes then the vehicle can't transition into forward flight because it is too nose heavy.

2) Suction effects on the duct/barrel inlet are significant and may cause roll/pitch torques that can dominate the vehicle's stability/control in hovering and slow flight.

3) Momentum drag effects of the duct/barrel produce are huge velocity damping effect that makes this vehicle perform poorly in wind.

4) When descending, the airflow over the vanes may be insufficient adequate roll/pitch/yaw control.

These configurations can be made to fly in hover reasonably well if flown in light winds. Heading-hold gyros on all 3 axes will make it hover quite easily. The aircrafts shown in the photos are glow powered (0.61-0.90 cubic inch) and weigh less than 9 lbs. Each has a computer control system with gyros, GPS, etc.. and can autonomously fly to waypoints. These were built under governement contracts 4 years ago.

Steve Morris

[Sean Kinkade]

Here are some pics of some experiments from 2002 with contra-rotating systems minus any means of control. My tests were basically hand-held to see and feel processional forces and thrust chracteristics. I shelved the project until now. Now I have discovered a super lightweight way to make the nacelle unit from depron foam so I'm back on the project.

Sean

[Sean Kinkade]

Steve,

You're the same Steve Morris that dabbles in ornithopters too aren't you?
Go figure we should meet here. :D

I've seen your type of machine before. The vaned tractor configuration nacelle goes way back. I also recall Tom Hunt had a similar system mounted in his "Vertigo" airplane in the '90's which was featured in Model Airplane News. That type of design seems proven but it's not what I want.

I'm going a totally different route with a totally different type of stability system that won't be affected by rate of descent. Like I said, it's a dynamic system, and with a separate power source. My concepts are also MUCH lighter, falling into the new upcoming catagory that I hope to create called "Park Flying Platforms" ( PFP's).

I will struggle for as strict of an adherence to the pure Jonny Quest look as possible for aesthetic reasons. I'm sure I will run into hurdles though! That's okay though. I'll keep at it until I succeed.

One expense issue I already may have is concerning heading hold gyros vs. non heading hold. If I can get three non heading hold micro piezo gyros to work, the cost of the machine can be held down. If heading hold gyros are required, that may cost too much. Time will tell.

Sean Kinkade

[mlbco]

Sean,

I play with ornithopters occasionally and hope to scratch build another one sometime in the next year, but I'm not as prolific a builder as you!

You can use piezo gyros for stability by cranking up the rate feedback as high as you can go and see if that's adequate. Very high rate gain approximates a heading system, but it's not really the same thing. The ugly yellow protoype shown in my photos used piezo gyros which were digitally filtered to act like a heading system over a roughly 30 second period. If you build the 3 gyros onto a board with a PIC processor, you can code a " washed out integrator" filter for each gyro that will give an acceptable short-term attitude feedback response without being affected by the long term drift of the piezo gyros. This is dynamically similar to how a flybar stabilizer works on an RC heli. I could send you a block diagram if you're interested.


Steve

[Sean Kinkade]

Steve, your kind suggestions sound a bit over my head at this point. I'll try my control system with basic micro piezo gyros first and see what it does. One step at a time.
If it's a complete disaster I will be all for seeing your block diagram. I was hoping to NOT have to make the equivalent of a "Piccoboard" for this type of machine but I may wind up having to.

Sean

Sean

[Sean Kinkade]

Another possibility for control is to contruct a type of "tilt to control" weight shift system which is what the Hiller Flying Platform used. The Hiller machine utilized a persons inate sense of balance.

You had the gyroscopic stability of the props below, and the pilot suspended high above it in standing position using subtle weight shift to control it. There were two engines, one for each prop drive, and the pilot controlled yaw through relative engine/prop RPM via throttle control.

In some of the Hiller flying platform photos I see a short control vane system was added beneath the nacelle, maybe these were added later for better control or to keep the craft in forward motion. I read one of the shortcomings of this machine was that it would "self correct" and go back to a hover no matter how much the pilot tried to keep it tilted and moving forward.

But before I attempt weight shift control I'll try vectored thrust control
which hopefully won't be effected by the ducted fan suction, nor the ducted fan thrust if it operates as planned.

Sean

[bob w]

Hey guys, a real easy way to show heavy end on top balances better is to use a baseball bat , Try to stand it on one end and balance the try the other.

[Miderror]

There you go Sean thinking out of the box again.
Get back to making those birds. :D

Take care,
Don Miller

[Sean Kinkade]

Don Miller!

I got another idea along the VTOL lines.........

Imagine a big hollow cyliderical depron "rocket", about 1 foot in diameter by about 6-7 feet tall with about 8 contra rotating prop mechanisms inside doing a slow-mo lift off...scale looking like the Apollo 11. Cool huh?

The Jonny Quest hover bucket comes first though. Hide and watch.:)

Sean

[Corbin_Dallas]

Okay, based on the very first post with the 3d model and the basic Idea of controlling the counter fins.... I'm not sure if any of you have seen the Vectron ultralight or hover copter toy ufo's that are setup like this and only have 1 channel up/down control. There is a thread on/about a developing way to controll one of these.

The big issue I see with this idea is this:
The base/can with fins makes the thing lift up by useing the counter-torque from the main motor/proppeller-----THUS spinning in the oposite direction
^^now, putting the emphasis on the word SPINNING, basically the whole model is going to be in a fairly high-speed spinning motion, spinning one direction or the other (fast enough to make the thing lift off)

THEREFOR, even IF you make the counterrotating fin things controllable, the BIG ISSUE I have had/seen/know of is with everything spinning, THERE IS NO FRONT/BACK/SIDES of the thing in flight!! So yeah it might do something when you move those added servos, but it and you have no FRONT of the model for either knowing where forward is, so putting what you think of is forward input would result in it moving in a (unstable) outward spiral type motion. Because if you make a mark on then surrounding 'CAN' to mark where you consider the 'front' should be....... as soon as you get it in the air you realize that the mark is spinning360º and so forward......... yeah, an outward spiral is what I envision with a forward input to this design.

Unless this "PENDULUM" You guys keep referring to means the controllable fins are on a ballbearing type connection to everything else (not effected by the spinning) and it stays stable without spinning along with any of the rest of the model, this dangleing part could then have a designated 'front' and move forward/backward/etc. if constructed right to make possible..>is this the 'Pendulum'?

[Stef]

Check out this site http://www.phlatboyz.com/ look at "NightOwl" has video and stills. Not much action since first posted but has poaaibilities.