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Old Nov 17, 2011, 12:14 AM
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Kinkade's Avatar
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Idea
New RFS system

I have a new ornithopter concept but I'm not going to go into extreme detail here about it again right now. I had just spent an hour typing a long thread only to have the thread dumped in the process of logging back into RC Groups.
RC Groups automatically logs me out after a short period of time. Is there anyway to click on "keep me logged in" like they have on Facebook etc.?

Anyway, here's the basic sketch and description. I call it a "Random Flapping Stroke" system. I consists of two gear motors driven off the same battery and ESC. They each have a crankshaft that drives a single swiveling horizontal plate. The wing conrods tap off the central pivot point on the horizontal plate which rides in a slot keeping the wings in unison. The gear motors however, are allowed to go in and out of sync at random. This should result in the wing stroke going from full stroke gradually down to little movement at all and back to full stroke at random as the motor speeds will not possibly stay exactly the same.

So, both gear motors in phase = full wing stroke flapping.
Motors 180 degrees out of phase means horizontal plate toggling which means virtually no flapping..locked in a power-on glide, although temporary until the motors fall back into phase and the wings start flapping again.

I'll post more on this concept later. It could lead to something interesting.

Here's a crude sketch.
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Old Nov 17, 2011, 12:36 AM
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This idea may lend itself best to a small electric free-flight ornithopter. It would give you automatic intermittent flapping and gliding with no external inputs.
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Old Nov 17, 2011, 01:58 PM
There's magic in those wings !
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Quote:
Originally Posted by Kinkade View Post
It would give you automatic intermittent flapping and gliding with no external inputs.
This is what I had in mind when I was reading your post ... I remember seeing a similar intermittent flapping rubber powered ornithopter that was flying just like you described .. I agree it will look more natural .. more alive

If I had been something big, I wouldn't have hesitated for a second to fund you, so you can realize all those concepts .... while still producing your current SK Ornithopters... by your own self-running other company

Khaled
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Last edited by khaled_abobakr; Nov 19, 2011 at 04:06 PM. Reason: grammar mistake ...
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Old Nov 17, 2011, 02:02 PM
There's magic in those wings !
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On another note Mr Sean ...

Sometimes I tell myself you don't like making a power bird because it will lack the graceful flight of real birds which is the true magic about flapping flight .. I agree I'd like to fly an eagle that flap slow and still can penetrate high winds with authority .. something that gives me the feeling of flying your SH in dead calm day but in a windy day ... Thanks god These calm days are still available

Khaled
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Old Nov 18, 2011, 04:24 PM
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Quote:
Originally Posted by khaled_abobakr View Post
This is what I had in mind when I was reading your post ... I remember seeing a similar intermittent flapping rubber powered ornithopter that was flying just like you described .. I agree it will look more natural .. more alive

If I had been something big, I wouldn't hesitated for a second to fund you so you can realize all those concepts .... while still producing your current SK Ornithopters... by your own self-running other company

Khaled
Khaled,

Where have you seen a rubber powered ornithopter with intermittent flapping?
I've never seen one.

I appreciate the fact that you would want to fund me and my concepts if you had the means. Thanks.
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Old Nov 18, 2011, 04:31 PM
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Khaled, don't worry I WILL make a PowerBird and soon!

For starters all a PowerBird would need to be is a beefed up Slow Hawk.
I think the gears can handle a lot more load so to make it a basic PowerHawk / WindHawk it needs more weight and power, plus a wing sail with a small inner triangle section. That would mean thicker wing spars, heavier duty conrods, and a bigger more powerful motor and or more cell count on the battery.
That would probably make it fly a lot faster and handle wind a lot better. But, I did have in mind building a Slow hawk size bird with my quad gear drive which could handle twice power.
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Old Nov 19, 2011, 05:58 AM
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go for the quad imho more bullet proof and heaps of power
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Old Nov 19, 2011, 06:33 PM
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Yes. That sounds exciting!
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Old Nov 20, 2011, 02:47 AM
There's magic in those wings !
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Quote:
Originally Posted by Kinkade View Post
Khaled, don't worry I WILL make a PowerBird and soon!

For starters all a PowerBird would need to be is a beefed up Slow Hawk.
I think the gears can handle a lot more load so to make it a basic PowerHawk / WindHawk it needs more weight and power, plus a wing sail with a small inner triangle section. That would mean thicker wing spars, heavier duty conrods, and a bigger more powerful motor and or more cell count on the battery.
That would probably make it fly a lot faster and handle wind a lot better. But, I did have in mind building a Slow hawk size bird with my quad gear drive which could handle twice power.
I'm so interested in seeing how the wingsail will look like .. I'm sure there will be more than just altering the area of the inner and outer triangles .. maybe bridging thrust battens, thicker battens ... m or maybe a larger flapping amplitude by increasing the crank length .. I don't know you're the master

Khaled
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Old Nov 20, 2011, 02:53 AM
There's magic in those wings !
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Originally Posted by Kinkade View Post
Khaled,

Where have you seen a rubber powered ornithopter with intermittent flapping?
I've never seen one.

I appreciate the fact that you would want to fund me and my concepts if you had the means. Thanks.
Hi Mr Sean ..

The video is on youtube somewhere .. I just couldn't find it, it was you who commented on how it was intermittently flapping/gliding during the end of the flight where there is no enough energy stored in the rubber band to make it flap continuously ... I'll post the video here once I find it ...

Khaled
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Old Nov 20, 2011, 02:52 PM
There's magic in those wings !
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Here it is ...

Free Flight Ornithopters 1993 1997 (1 min 59 sec)


Isn't it amazing how it locks in a perfect glide for a moment then resume flapping , then glide and so on ... ...

Khaled
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Old Nov 20, 2011, 03:14 PM
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Yes, I remember this now! I also remember liking this but I had completely forgot about it. That's a neat bird. Now see how it glides like that between flaps? Maybe my system would also do that. I think it needs to be built and tried.

From what I see of this modified TIM bird, although cool,I don't think that the intermittent flapping effect was neccessarily intentional. It looks to me to be more of a by-product from installing over size wings that overload the rubber band. The porpoising motion of the bird causes the wing loading to change and that causes the flapping drive to lock up temporarily.

I also installed a set of oversize (membrane) wings onto a TIM bird back in the mid 1990's but while the loading slowed the flapping down, it never did lock up the flapping like this other one. It's the long moment of the wings that's causing the lock up effect. My wings were not so long. Mine had straight carbon rod spars and ripstop fabric wings like my larger RC birds. It flew great too and it's amazing just how strong the TIM bird flapping mechanics are. My problem however was with the special elastic bands that came with the TIM bird. No rubber bands I tried would work properly yet the elastic bands which did work would not last under the additional loads. I would get a few nice long flights and then the elastic would break. I knew of no way to remedy this so that ended the project. I still don't understand why the Van Ruymbeke's never made larger slower flapping wings for their ornithopters...something I personally find more aesthetically pleasing than fast flapping wings.

But anyway, yes! The RFS system has promise I think.

That was Steve Morris right? He's done a lot of neat stuff.
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Old Nov 20, 2011, 03:24 PM
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Actually in the RFS system the motors could run in the same direction or oppositely. I guess it wouldn't really matter. It's just the fact that they are not mechanically coupled and can fall in and out of sync that makes it work.

After seeing that modified TIM bird again, it makes me think maybe a more built up glider style wing may benefit a lot from the RFS device...something with a good glide ratio will cruise along during the fixed wing periods instead of just losing altitude.

One good thing you can see in my sketch is that when the output cranks do go out of phase the wings have no choice but to place the central piviot point at center which puts the wings in a flat glide. So as long as you have power on and the motors fall out of phase, you WILL have a guaranteed glide lock. It would be great if you could throttle down at that moment to retain the glide lock position indefinitely but unfortunately at this point I don't think that will work because once the power is shut off the wing forces can still pull one motor crank or both to top dead center which would mean a pigeon glide. It's only the fact that power is on during the out of phase toggle that prevents the wings from going to pigeon mode. Maybe there is a way to make a ratchet lock device on this too. I'll have to see.
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Last edited by Kinkade; Nov 20, 2011 at 03:40 PM.
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Old Nov 20, 2011, 03:29 PM
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Yeah, mlbco.
Steve still visits this forum from time to time. But I guess between his drones and gliding, he doesn't experiment much with ornis anymore.
Then again, I don't know him personally, so I shoudn't say that - just because he hasn't shared anything recently doesn't mean there aren't a couple of projects he's been hiding.
I thought his old projects were pretty cool. Like von Holst.
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Old Nov 20, 2011, 03:30 PM
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I saw him often enough. He's busy with his own UAV company
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