An ornithopter is a lot like a model airplane, but it flaps its wings like a bird or an insect, and is a lovely sight to watch in flight.
This is pretty easy to build; you really only have to make sure the bearings are all parallel. Everything else can be crooked and this will STILL fly just fine. It is also VERY sturdy and can take many, many crashes without breaking. As an added bonus (and due to my personal tightwaddery) it is CHEAP. You can make this ornithopter out of household items. Mine cost about $1.30 to make.
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Bamboo Place Mat -- $1 at the local dollar store. We bought one too many for our table.
Gel Super Glue -- $1 for a 3 pack at the dollar store. Found it in a cupboard.
Plastic Grocery Bag -- Usually use them for tying up stinky diapers.
Coffee Filters -- Free from work (I don't drink coffee). And, no, I didn't steal them.
White School Glue
Clear Tape -- All free stuff I found lying around
CA accelerator -- $4 at the local hobby store. Sets super glue almost instantly.
Step 1: Assemble the Body
Start by removing some flat bamboo strips from the place mat and laying out the body shapes. I made some triangles. Using a pencil, carefully mark lines where they overlap. Cut along the lines with your dikes. Carefully clean up the edges with a knife. Glue together with a bit of superglue and spray with accelerator.
Continue for all the joints.
Step 2: Assemble Crank Supports
I made some thin support pieces by cutting the bamboo in half lengthwise.
Step 3: Add Bearings
When you have three bearings, make some bearing support pieces as pictured. Glue a bearing to the bottom of the body. This is the main crank bearing. Glue two bearings to the top, side by side in the channels created by the support pieces. These are the wing bearings.
I found it helpful to slip a couple straight pieces of paperclip inside the bearings as I was positioning them. This helped me ensure they were all parrallel.
Step 4: Reinforce Your Joints
Step 5: Finish the Body
After flying and crashing my ornithopter for several days, it broke right at the weak point between the triangles. So I added a third spar high enough to avoid the rubber band motion. I recommend you add one as well, as pictured.
Step 6: Make Wing Spars
You can make a drill by squishing the end of a paper clip and cutting it at an angle with dikes. Bend into a stepped shape and hand crank away. I made a motorized drill for this project from a VCR motor I had lying around and a thumbtack. Super glue the tack to the motor, squish the tip with pliers, and cut at an angle. Attach to 9-volt battery. I found the VCR lying beside the road a few years ago and scavenged it for parts before I threw the case away.
Form two wing cranks from paperclips as pictured. The little "jog" in the left wing crank allows good wing movement. Insert cranks into wing spars and superglue in place. Reinforce with a layer of tissue. Take two smaller pieces of bamboo and drill several holes at regular intervals. These will be the adjustable arms.
Insert the left and then right wing spar and slide the adjustable arms onto the wing and main cranks. Test wing movement. You might have to add a piece of Bic ink tube as a spacer to one of the wing cranks for easy movement.
Disassemble wings and adjustable arms.
Step 7: Make a Crank
Make a bead for the crank from a Bic Pen. Pull a Bic pen apart with pliers. Cut off a few rings of the ink tube. Fill the rings with super glue and let dry. Slide one onto the crank handle and glue in place with super glue. Be sure not to get any glue on bearing.
Step 8: Make the Tail
Using similar techniques as before, cut and glue two bamboo pieces together at an angle for the tail booms. I also thinned my tail booms to cut down on weight. Glue a large, straightened piece of paperclip as a tail boom. Cut a small circle out of tissue and reinforce the joint with it. Carefully cut the tail out of the grocery bag with a sharp knife. The tail should be about 6.5 inches long. Super glue the tail to the tail spars.
Step 9: Attach the Wings.
Insert the left wing into the left wing bearing. Insert the right wing and make sure that the wings can move freely. You might have to add a bit of ink tube as a spacer. When you have them moving well, remove the right wing. Glue the left wing to the the "spine" of the body. Add the right wing and just tape the centerline of the wing flaps to the left wing.
Step 10: Final Assembly
Hook a rubber band onto both hooks.
Step 11: Test Fly and Trim
Here's my second test flight:
If your ornithopter zooms upwards and stalls, try adjusting the tail boom down a bit. If it still stalls, you may need to tape a coin to the front of your 'thopter.
If it turns in a slow circle, you can tape a piece of wire to the wing tip on the outside of the turn. I left my wing spars long, and so I just cut off excess from the wing tips on the inside of the turn to fix that.
Experiment with different arm lengths (you know, the adjustable arm) and different rubber bands. I found that two or three narrow rubber bands gave me more consistent torque than one thick band (and also lasted longer).
Now go play with it! My daughters love watching this thing.
I've added a couple pictures to show where to attach the rubber band (actually, I use four regular rubber bands at once) and where you wind it up.