http://img225.imageshack.us/img225/2489/minijp320dg.jpg

Do you think its possible to build a flying machine capable of carrying a person that operates with flapping wings. I've been obsessed with this idea for many years. I think Pterosaurs first built up my interest.

http://img108.imageshack.us/img108/3747/pterosaur250sz7.jpg

I tried to build an elaborate flying machine one time. Two circular wings one above the other. Each allowed air down through it but acted like a parachute trapping any air trying to go up through. Essentially large one way valves.

The idea was for them to flap up and down in opposite directions so one would always be moving upwards easily while the other dragged downwards against trapped air. The passenger would hang underneath this sturdy double parachute assembly. Unfortunately the materials proved unsuitable. Might try it again some day.

I saw an old contraption working on a similar idea in a black and white movie and got quite excited. It was clearly the same idea in the inventors head. But he only had one umbrella like fixture and a piston engine drove it up and down. Far too heavy to work.

The trouble with copying birds is that the length of the wings would be too great and the stress would snap most materials.

I had a flapping toy bird that flew when I was a kid. It was powered by an elastic band, and you chucked it, released the flapping mechanism and it would flap around happily for 30 seconds or so.

Looks like the idea has had a makeover since my youth;

http://www.gogo-gadgets.co.uk/index.asp?function=DISPLAYPRODUCT&productid=569

Whether it would scale up is another question.

It would be very inefficient I would say. Instead of generating lift by the upward pressure generated from the forward motion of an aerofoil, you would have to generate lift mechanically(that is, by flapping) Have you ever tried to flap an aerofoil? It just doesn't work, therefor the wing would have to be mosty concave shaped - like a birds. This at the sacrifice of the aerofoils more efficient method.
Also controlling the craft manually at any efficiency would be impossible, a bird makes many tiny adjustments each second to keep a straight course - Easy for the bird to have perfected over millennia of evoluton but not so easy for say a computer to emulate.
The whole thing would be an inefficient ungainly mechanical nightmare and would probably flap its self apart IMHO.

The fundamental problem is one of mechnical engineering. When scaling a device, weight goes up as the cube of the scale, while strength only goes up as the square. This puts a limit on how far you can scale up something like a flapping wing flying machine (ornithopter?).

"but not so easy for say a computer to emulate"

Au contair, a computer could emulate it quite easily... given the right programing and data. However, humans on their own would have a tough time. Ever heard of the B2 Bomber? The only reason that thing flys is because of computers. If the computers were taken out, the thing would not be able to stay in the air. It has to make thousands of adjustments for it to fly stably.

why?

You know, if you ended up in a wheelchair, I bet you could get a doctor to remove your legs. That would remove a bunch of weight.

Fasting would also help.

This technology has been addressed in sci fi often enough that a standard word has been coined for it: ornithopter. Conventional scientific Greek derivation: bird + wing. There's no reason it could not be built with today's technology. The problem with it is simply horrible energy inefficiency: the wings are not just propelling the aircraft, they are dragging huge masses of air up and down. As the incredibly slanted windshields and little spoilers that are popping up on cars remind us, pushing and pulling blocks of air wastes a surprising amount of energy.

Ornithopters are modeled after birds--duh--so we should look to birds for our clues:1. Birds are mercilessly stripped of weight. Their bones are hollow. They have no teeth. They have feathers instead of fur. Their organs are as small and uncomplicated as they can be and still work. They have practically no immune system. Weight is such a huge disadvantage that evolution has made these remarkably cruel compromises to keep them light. 2. Birds are small. Most of them don't weigh five pounds, only a few species weigh more than ten, and they spend more time gliding than flying. 3. Flying is so difficult that it limits birds' abilities to do anything else well. Birds took to the air because there was no competition for the bounty of insects flying around and they rule that ecological niche. Yet the ones who moved back to the surface managed to do very well even with the competition. The really big ones, the ratites--ostritches, cassowaries etc.--can't fly at all. They readapted to an earthbound life and are surprisingly successful at it. The other group of big ones are the penguins, who stopped flying and readapted to an aquatic life, at which they are also successful. 4. Birds eat a lot. Small birds eat something like a third of their body weight every day. Flying uses an enormous quantity of energy. 5. Wings are huge. Large birds like eagles have wingspans much larger than their bodies. Condors look like giant wings with no bodies. Jet airliners have wings about the size of their fuselages. A bird the size of an airliner would probably need a thousand-foot wingspan--and a breastbone the size of a locomotive to anchor them.So the problem with building a working ornithopter is that it would have no practical use. An ornithopter large enough to carry the pilot and an observer would weigh about twenty times as much as the largest flying bird. The wingspan would surely be as great as a jetliner, making it awkward to launch and clumsy to fly. The fuel consumption would be staggering. The power reserve for emergencies would be virtually zero, The fuel capacity would be limited because of the extra weight, so long flights would not be available.

It would certainly be fun, but it would cost a fortune to provide just a little bit of fun.

Au contair, a computer could emulate it quite easily... given the right programing and data.
have you ever tried to write an intelligent control algorithm? that shit ain't easy to do on a simple wheeled robot, very complex on a standard aircraft, and mindbogglingly difficult on a b2 that flaps its wings. however, you are right, it could be one.

the problem would be a mechanical one. like was said before, the strength does not scale up as much as weight. imagine you have the wings of say, a B2, you know how strong the wings/joints would have to be to flap those giant wings fast enough to make it fly?

I'm thinking that big birds don't get much lift from flapping; that flapping produces more forward thrust than anything else and they get lift from using their wings as aerofoils.

Why? [...does the B2 Bomber need continuous computer adjustment to fly]
Because it isn't inherently aerodynamically stable. A regular plane (or glider, or paper plane, or a dart, or a shuttlecock, or a well thrown discus, javelin, or frisbee) will fly a reasonably straight path with the controls fixed the central position. I think (I'm no expert and I'm talking off the top of my head) this is mainly because the centre of drag is behind the centre of mass, meaning that the air moving past the plane tends to align it nose-forward, and because the mass of the plane is distributed in such a way that it sits solidly on the wings (the support point).

A plane with a different design, eg with centre of mass behind the centre of drag, and precariously balancing on the wings, would not fly straight with the controls fixed. It would tend to fall over like a pencil standing on end, and flip around like a shuttlecock thrown tail-first.

Some modern planes have unstable designs. This means that they are pretty much impossible to fly manually. It would be like reversing a caravan at 100mph - one tiny misalignment, and you're jackknifed and upside down! But they can be controlled by computer. Essentially the pilot tells the computer what they want the plane to do, and the computer drives the control surfaces in the right way.

The advantage of doing this is that it makes the plane incredibly maneuverable. The plane wants to spin around, flip over, or whatever... all the computer has to do is let is (and get it immediately back under control, of course).

know how strong the wings/joints would have to be to flap those giant wings fast enough to make it fly?The giant wings would not have to flap as fast as we might assume. Large birds don't flap their wings nearly as quickly as small ones. Extrapolating from what I see in eagles (never seen a condor in flight), I would guess that a bird the size of an airplane would flap less slowly than 60bpm.

"why?"

"Fly-by-wire means that you are flying the computers (four of them, in this case), not the control surfaces themselves. Quadruple redundancy means that, in effect, the four computers "vote" on the result of any given control input by the pilot—at least three must agree, and any anomaly is automatically thrown out.

The beauty of a system like this is that all sorts of conditions and compensations can be programmed in. For example, the B-2’s bomb doors set up a huge amount of drag when they are opened. When a heavy bomb load is dropped, the plane will want to jump, yet the flight controls automatically compensate for both of these effects, and the pilot has only to operate the throttle. "

http://www.edwards.af.mil/articles98/docs_html/splash/jan98/cover/page_5.html

I'm thinking that big birds don't get much lift from flapping; that flapping produces more forward thrust than anything else and they get lift from using their wings as aerofoils.


Have you ever even looked at the a birds wing? It is not an aerofoil!

they gain lift combined with forward motion due to flapping. Ocassionaly they use thermals to gain lift also. How would you suggest they would generate the forward motion to gain any significant lift from a rigid aerofoil anyway? Beak propeller? WAFD!

The giant wings would not have to flap as fast as we might assume. Large birds don't flap their wings nearly as quickly as small ones. Extrapolating from what I see in eagles (never seen a condor in flight), I would guess that a bird the size of an airplane would flap less slowly than 60bpm.
unless you take weight into consideration. even aircraft aluminum would be quite heavy, requiring faster flapping, which would make it need to be stronger, which would add weight, which would make it have to flap faster, which... you get the idea. anyway, 60bpm would require some seriously strong material, not to mention the wear the joints would take.

My question was why would you want to make a flapping flying machine, but I thought of why. It could be useful at a small scale. Unmanned vehicles would appear to be birds, and thus achieve a higher degree of stealth. At a very tiny scale, they could look like insects.

have you ever tried to write an intelligent control algorithm? that shit ain't easy to do on a simple wheeled robot, very complex on a standard aircraft, and mindbogglingly difficult on a b2 that flaps its wings. however, you are right, it could be one.

the problem would be a mechanical one. like was said before, the strength does not scale up as much as weight. imagine you have the wings of say, a B2, you know how strong the wings/joints would have to be to flap those giant wings fast enough to make it fly?
They can get 'Asimo' to walk, but can they get him to run ?

Plenty of other robots have mastered running. Asimo may be famous, but there are many other research bots out there with better walking abilities. Specifically, the amount of energy/distance used in Asimo is horrible. Humans shift their weight and basically are in a continual fall when walking. This saves a lot of energy.

-AntonK

Plenty of other robots have mastered running. Asimo may be famous, but there are many other research bots out there with better walking abilities. Specifically, the amount of energy/distance used in Asimo is horrible. Humans shift their weight and basically are in a continual fall when walking. This saves a lot of energy.

-AntonK
There has been much experiment in it, but I believe you are wrong. There has never been a robot that could stably and sustainabally run unaided. If there is cite it please.

Have you ever even looked at the a birds wing? It is not an aerofoil!
:bugeye: Do you know what an aerofoil (http://en.wikipedia.org/wiki/Aerofoil) is? A bird's wing is the classic example of a natural aerofoil. Try googling bird airfoil (http://www.google.com/search?hl=en&lr=&q=bird+airfoil&btnG=Search).

they gain lift combined with forward motion due to flapping. Ocassionaly they use thermals to gain lift also.
Like I said, I'm thinking that for large bird, flapping is more for forward motion than anything else. Yes, they obviously get lift from flapping as well. For large birds, I think that thermals are used much more than "occasionally".
How would you suggest they would generate the forward motion to gain any significant lift from a rigid aerofoil anyway? Beak propeller? WAFD!
Ever heard of a glider? :D
Ever watched a large bird fly?
Ever heard of flapping to generate forward motion? I think someone mentioned it in this very thread :rolleyes:

My question was why would you want to make a flapping flying machine, but I thought of why. It could be useful at a small scale. Unmanned vehicles would appear to be birds, and thus achieve a higher degree of stealth. At a very tiny scale, they could look like insects.

If you could get them to move in random or pseudo-random motion, like butterflies, it would be extremely difficult to shoot them down.

http://images.google.com/imgres?imgurl=http://www.global-defence.com/2000/images/uav2jpg&imgrefurl=http://www.global-defence.com/2000/pages/uav.html&h=97&w=155&sz=7&hl=en&sig2=3fwCU2tw871s0DUzI5oO_Q&start=1&tbnid=9GT9CrmQCc26MM:&tbnh=61&tbnw=97&ei=mB4jRan5O5vwiQHBj4mBCQ&prev=/images%3Fq%3DMicrostar%2Buav%26svnum%3D10%26hl%3De n%26lr%3D%26safe%3Doff%26sa%3DG

:bugeye: Do you know what an aerofoil (http://en.wikipedia.org/wiki/Aerofoil) is? A bird's wing is the classic example of a natural aerofoil. Try googling bird airfoil (http://www.google.com/search?hl=en&lr=&q=bird+airfoil&btnG=Search).


Like I said, I'm thinking that for large bird, flapping is more for forward motion than anything else. Yes, they obviously get lift from flapping as well. For large birds, I think that thermals are used much more than "occasionally".:
Yes but I meant the ocassional species uses thermals dumb ass. Most birds dont use them and/or are not species that glide.
Hes an true aerofoil TYI:
http://en.wikipedia.org/wiki/Aerofoil
Ever seen a humming bird or any small birds for that matter? they dont keep the wings still enough to use as an aerofoil. Even if it was shapes in a significant enough shape to be a worth while option.

Ever heard of a glider?
Ever watched a large bird fly?
Yes and a glider uses thermals only to gain lift, it manages nothing more than to minimalize descent with its forward motion through non thermal areas. You try and get a glider to climb in non thermal airspace and it will just stall. :rolleyes:

Ever heard of flapping to generate forward motion? I think someone mentioned it in this very thread
:rolleyes: Yes it was me that first mentioned it dick, but how to you take advantage of the areofoil effect if the wing is in motion? You cant!. Study the aerofoil effect and you will see that it requires a static surface not only that it needs to be prone with a leading edge higher than the trailing, to gain lift.

Yes but I meant the ocassional species uses thermals dumb ass. Most birds dont use them and/or are not species that glide.
Hes an true aerofoil TYI:
http://en.wikipedia.org/wiki/Aerofoil
Ever seen a humming bird or any small birds for that matter? they dont keep the wings still enough to use as an aerofoil. Even if it was shapes in a significant enough shape to be a worth while option.

Yes and a glider uses thermals only to gain lift, it manages nothing more than to minimalize descent with its forward motion through non thermal areas. You try and get a glider to climb in non thermal airspace and it will just stall. :rolleyes:


:rolleyes: Yes it was me that first mentioned it dick, but how to you take advantage of the areofoil effect if the wing is in motion? You cant!. Study the aerofoil effect and you will see that it requires a static surface not only that it needs to be prone with a leading edge higher than the trailing, to gain lift.

Makeing ad hominem attacks like that adds nothing. Especially considering that even if you may disagree with his statements, Pete made no attacks on you. While I have no formal authority on this site, I think most people would agree that your presence here is not necessary if you want to make unwarranted personal attacks.

-AntonK

Ad hom petes ass!

Hi Imaplanck,
I'm sure you're a bright person, but taking offense when someone thinks you're wrong might not be a clever thing to do.

I'm sorry for any perceived insult. Please understand - I'm not attacking you, I'm attacking your idea. Perhaps I'm wrong. Perhaps you're wrong. Perhaps neither or both of us are wrong, and we're misunderstanding each other. But we'll never find out if our discussion degenerates into calling each other names.

In this thread, the question is whether flapping is any use for lift at large (human size) scales. In my original post, I extended the question to birds, and considered whether large birds flap their wings more for thrust or for lift, and whether they get more lift from flapping or using their wings as aerofoils.

I think that you and I both understand the cases in which bird's wings are and are not aerofoils:

Bird flapping - wings aren't aerofoils.
Bird gliding - wings are aerofoils.

We also understand how small and large birds use these cases differently:

Small birds - flap more, glide less
Large birds - flap less, glide more

In summary, I think that you and I agree that:
Small birds flap mainly to provide lift.
Large birds flap mainly to gain or maintain airspeed.
Bird wings are aerofoils only when they are gliding.
Flapping for lift is OK at small scales (insects and small birds), but the energy efficiency drops off as scale increases.
The largest flying birds are probably about the upper size limit for useful flapping.
Human scale flapping would be very inefficient.

Pete

http://img225.imageshack.us/img225/2489/minijp320dg.jpg

Do you think its possible to build a flying machine capable of carrying a person that operates with flapping wings. I've been obsessed with this idea for many years. I think Pterosaurs first built up my interest.

http://img108.imageshack.us/img108/3747/pterosaur250sz7.jpg

I tried to build an elaborate flying machine one time. Two circular wings one above the other. Each allowed air down through it but acted like a parachute trapping any air trying to go up through. Essentially large one way valves.

The idea was for them to flap up and down in opposite directions so one would always be moving upwards easily while the other dragged downwards against trapped air. The passenger would hang underneath this sturdy double parachute assembly. Unfortunately the materials proved unsuitable. Might try it again some day.

I saw an old contraption working on a similar idea in a black and white movie and got quite excited. It was clearly the same idea in the inventors head. But he only had one umbrella like fixture and a piston engine drove it up and down. Far too heavy to work.

The trouble with copying birds is that the length of the wings would be too great and the stress would snap most materials.


Of course it is possible. Your question is incomplete. You may have had in mind to mention something about its efficiency. Why don't you ask it again?