(No video because I ran out of bands in prototyping, and I need to get this posted before the deadline.)
Step 1: Materials and Tools
- Three paperclips. I used large ones that opened out to 15cm long, but I see no reason why this wouldn't work with ordinary clips.
- An elastic band, sized to match your clips (the ones I used were 6cm long).
- Paper - stiff and light for preference.
- Pliers (two pairs could make life easier).
- Glue or tape.
- Scissors or craft knife.
Step 2: Making the frame
Bend one clip to an angle of 90o - this will support your front wings.
Bend the second clip 90o as well, but then bend the wire back 45o on each side of the first bend, making a straight wire with a V notch in the middle - this will support the back wings.
The third clip is much more complicated:
- Turn a small loop in the middle of the wire (I wound it round the handle of a small paintbrush).
- Bend the straight sections so that, when the loop is held horizontal, the straight legs point vertically down.
- Bend the ends of the legs into an L (on the same side as the loop) and then bend the bottom of the L into a small V.
Step 3: Building the frame.
Place the V between the two bent parts of the L you made, and use the pliers to clamp the Ls tightly over the wing-clip. Make sure that the point of the V is pointing up into the frame.
You are now ready to add the band and the wings.
Step 4: Design the wings
I lay the frame on the paper, and sketched roughly what I wanted the wings to look like. When I was happy, I firmed up one side of the butterfly in marker pen, allowing for tabs to fold over and glue.
I then folded the paper in half to cut it out, thus making two identical-but-mirrored sets of wings.
Step 5: Add power
Attach the band to the rear wing-clip with a lark's head hitch, then thread it through the loop at the other end of the frame, and thread the front wing-clip through the band.
Step 6: Add wings.
Make sure that the wings do not foul the frame or each other when they turn.
You could, of course, decorate your wings, but I would use ready-decorated paper (if I had any), such as the colourfully-marbled origami papers you can buy.
Step 7: Winding and flying
Hold the butterfly flat between the palms of both hands, and toss it into the air as if releasing a dove.
Both sets of wings will spin in opposite directions (if one set is larger, it will spin more slowly than the other pair), and the flat wings will bend, forming a pair of crude propellers - they work together, even though they're spinning in opposite directions.
The loop you made at the top of the frame is like a section of a helix; the front wings might catch on it, so you might find that the butterfly works better if you wind it one way and not the other.
Step 8: Oh, no!
Unfortunately, accidents during prototyping reduced me to just one last band. After test flying the final model, I decided to wind it just a little tighter to make it fly really well in the video.
I snapped the band.
Still, here it is, ladies and gentlemen, for your consideration - the rubber band powered butterfly.
Double oh no! - this isn't as original as I thought. I was just googling for some images of butterflies, intending to draw on my finished wings, when I came across an existing rubber-band powered butterfly make. It's not exactly the same as mine, but identical in the flight mechanics. I hope this doesn't preclude me winning, but if it does, it was a fun make anyway.