Introduction: An Ornithopter

About: I have always loved the feeling of finishing the construction of an object and if I don't have something I need or want I usually give it a go to build it from what I have. Usually though, I look at a boring o…

I have made many ornithopters before and after the one I will show you how to make in this instructable, but this one is still one of my best because it is stronger than my lighter all-balsa wood ones.
This one is of the more conventional ornithopter layout, with flapping wings in the front and a birdlike triangular tail. There are other layouts which I may also decide to make instructables on, which have the elastic in front of the wings or have dragonfly wings or look like 1490s Leonardo da Vinci designs.
I make most of my ornithopter frames from balsa now because it greatly increases flight time but I doubt everybody who wants to make one of these has balsa wood, so this one is the better option for most people.

To make the ornithopter in this guide, you will require;
- Chopsticks (or kebab sticks)
- Thin wood of some kind (I use Ice-cream sticks or balsa offcuts)
- Pins or thin, stiff wire
- A thin tube (I use the insulation from a paperclip or a clutch-pencil tube) for the pin/wire to fit into.
- A plastic shopping bag/packet (NOT the stiff or thick plastic kind, only the very thin kind)
- Plastic (from an Ice-cream container or something) about 1 millimetre thick.
- A small bead to fit onto the pin/wire
- An energy-drink can (only aluminium cans will work, DON'T use a steel can)
- Sticky tape
- Strong glue
- An elastic / rubber band
- Scissors
- Pliers
- Craft knife or scalpel

I did not include measurements because (A) I don't use them and (B) Your ornithopter will probably be a different scale to mine. Use the photographs for scaling.

Step 1: The Frame

This part takes a bit of time to get right but it is pretty basic. Sorry I didn't take any pictures before these so I cannot show you how I made the parts of the frame, but I will explain it as well as I can.

The main fuselage beam (Labelled in first picture) Was an Ice-cream (Popsicle) stick which I trimmed to size and sanded. Try to keep it as light as possible without harming its structural integrity.

The part labelled "mast" is made in the same way, but it does not have to be as strong so lighten it more. The ratio between the main beam and this in length is about 2.5 to 1.

For the drive system, glue a small piece of wood under the main beam where shown and glue some kind of tube under it. I cannot be specific about the tube because I use whatever I have lying around at the time.

For the crankshaft, bend a pin or piece of stiff wire into the shown shape. Start with the hook end. Once the hook is the correct shape and balanced, put the other end of the wire/pin through the tube. Thread a small bead onto this end and bring the hook as close to the back of the tube as it will slide. Also slide the bead so that it touches the tube.
Hold the wire (in front of the bead) with narrow pliers and bend a 90* bend into the wire. Make sure the wire can easily turn inside the tube before continuing. Bend the wire again where it is shown in the picture (also at 90*). It is critical that you get the distance between the 2 bends correct and to scale otherwise the ornithopter will make either a very big or very limited flapping motion. Leave about 1.5cm (2/3 of an inch) sticking forward. Test-wind the crank to check that it moves freely.

For the tail "hook" I use Aluminium from a Red Bull can but you could also make a wire hook.
For the aluminium one, bend a small rectangular piece of can in half and trim the "open" side. Glue this to the back end of the beam after squeezing the metal around the end of the beam.

Cut a piece of bamboo from a chopstick, etc. to the right diameter (guess which diameter will be strong enough, but lightweight) for the central wing rib. It must be the same length  as the main beam. Glue it to the top of the "mast" in line with the main beam.

Step 2: Wings and Flap Actuating Mechanisms

The wing hinges and moving parts not yet mentioned are;
- Small tubes     X2
- Wire/ pins         X2
- Flap actuators X2
- Struts                X2
- Stops (tiny plastic tubes with glue works) X3
- Wing spars      X2

To make the hinges for the wings, bend 2 pins/pieces of wire into the 90* bend "Z" shapes in the first picture. Use the wing rib below them for scale, it is important that they are a certain distance out and they MUST be bent in exactly the same places or the completed mechanism won't be able to revolve. Then, insert the longer end of each into its own tube and bend the excess wire/pin to the side shown. DON'T let this part touch the tube and make sure to test that the wire part of the hinge can move easily in the tube. If it doesn't, then your ornithopter may stop flapping at an awkward time in the wing cycle and flip over and crash.

Glue the two of them on opposite sides of the top end of the "mast" with the wire end sticking out forward. Ensure that the tubes are glued parallel to the rib and main beam (see picture 4 for reference). DO NOT GET ANY GLUE INSIDE THE TUBES OR ON THE WIRE PARTS.

To make the 2 wing spars, cut/shave two kebab sticks to the same approximate thickness as the wing rib. Both must be about twice the length of the rib and they MUST be the same size as each other or the ornithopter will go in circles.
Hold one over the wire part of one of the hinges and mark where a hole will be made for the forward-sticking part of the wire hinge will go through. Repeat on the other spar. Use a sharp knife or pin or small drill bit to make a hole in the spot you just marked, the hole must just be able to slide onto the wire and it must be made all the way through the spar.

Slide each spar onto the wire part to make sure both fit, then glue them both in place (as shown in picture 5).

Now, the difficult time consuming part, the flap actuators. The shape is pretty basic, just a strip of plastic (from an ice-cream or yogurt carton) with a small hole made on both ends. You will need to make 2 of them so once you have made one, just trace it onto the plastic and make another exactly the same size.

Finding the correct length is the tricky bit and I always have to try a few different lengths to get one that works nicely. Do this by trial and error by holding a strip of plastic over the crank and piece of wire sticking out of the wing. Flap the wing  slowly by hand to estimate where the points should be. The flap upwards from horizontal should be about 30* and below horizontal about 20*. Once you get the length right, test the mechanism by manually winding the crank and check that the cycle is smooth and that the flap angle is correct. If it is, then glue stops onto the 3 pivot points (wire bits) to stop the actuators from coming off.

On this model, there is a small strut behind the base of the wing attached to the "bent-round" part of the wire in the hinge and the back of the wing spar (see the last picture in this step). Here it is also made of lightweight wood, but most of the models I have made since this one have a longer piece of wire behind the hinge and I just bend that to the wing and glue it there. Having a strut of some kind behind the base of the wing is very important because otherwise the ornithopter would be rendered un-flyable if the wing hinge bent back after a wing-strike.

Step 3: Tail, and Surface Covering

There are two main types of tail used on birdlike ornithopters, a flat 2-dimensional 2-sparred type and the type shown here. This one is slightly heavier but makes the craft fly in a more stable manner.

To make the tail shown here, cut some more bamboo sticks down so they are thin and lightweight. They can be a little bit thinner than the wing spars because they are less likely to be damaged in a crash and lightness is important. Three tail spars are needed, each about 3/4 the length of one wing spar. The outer two spars must have an angle between 30 and 60 degrees between them.
The middle spar must be evenly placed between the two outer ones, and a small piece of bamboo glued underneath to keep the angles correct and strengthen the structure. Once all of this glue is dry, snap the small piece of bamboo in the middle so that the tail now forms a wide "V" shape when viewed from behind. Add glue to the place you snapped it so that it keeps its strength. Now glue all 3 spars to the back of the main fuselage beam and make sure the back of the tail is slightly higher than the base.

To cover the wing surface for flight, hold the ornithopter upside-down on a thin plastic packet (Or tissue paper if you prefer) and draw the basic curved outline of the trailing-edge of the wing onto it. Draw a line a little bit in front of where the spar is so that it may be folded over the spar once cut out. Fold the shape of the one wing over and cut the shape out so that when you are done cutting the plastic bag you will end up with the shape shown in picture 4. Glue or tape this shape onto the top of the wing spars and rib. use the pictures after picture 4 for reference.

To cover the tail, draw cut out a triangle a bit bigger than the tail from the plastic packet. Put it over the tail and trim the edges down,  then glue or tape it to the top of the tail frame parts.

Your Ornithopter is now complete! To fly it, wind the crank in either direction until the whole elastic you are using looks knotted. Then release the mechanism to spin the other way and give it a light toss forward. It will usually travel in a circle as it flies so you don't have to fly it in a huge space. Watch out for any cats in the area that might steal it when it lands! =)

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