It is a self supporting rubber band powered engine shaft and blade. It is designed to fit a specific type of balsawood aircraft sold at Michael's craft store, but im sure it will fit any old thing you strap it to. Now you can play with the r-band powered craft as much as you want, and when it breaks, you can simply switch the prop over to a new plane! Here's how to make it....
1 proconstructed balsa wood airplane (I got mine from MIchael's crafts for $1)
1 long and one small rubberband
1 or 2 Lego propellers (the bigger the better)
a small paperclip
less than a foot of 1/4" dowel rod (use poplar or pine)
certain common Legos, pictured below
a dremel tool or something with simiar drilling and sanding capabilities
silicone spray makes it much faster
remove the nose weight
Step 1: Making the Rotary Shaft
1. get out your long rubberband and the three other legos pictured. A black ridged rod about an inch long, a gray friction nut, and a cylindrical hollow uni-bumb.
2. cut your rubberband and slide the ends through the top of the black uni-bumb.
3. slide the black uni-bump with the band in it onto the black ridged rod in such a way that the rubberband is also attached to the rod. Slide the gray friction nut onto the shaft, and put superglue between the nut and black uni-bump to help permanently attach these items to the black ridged rod.
4. (note in the photo i used a cylindrical unibump for this part, you should use two cubic unibumps)
get two cubic uni-bumps. you can lego lock them and glue them together to that the holes are facing the same direction.
5. Now get your propellors ready, and assemble the whole thing as shown in the first photo.
Step 2: Assemble the Balsa Airplane
the plane has a weight on the nose, take it off and keep it until the end. If your finished plane isnot balanced right and adjusting the main wing doesnt fix it. You can use this nose weight to rebalance it.
Step 3: Build the Support Shaft
1. cut the dowel rod to 4.75 "
2. use your dremel tool and a cuttoff wheel to cut a groove to half the depth of the rod, for the entire length of the rod. I set my rod onto a boxtop with a corner to help support it.BE CAREFUL. at one end cut a little deeper for about a 1/4"
3. use your dremel small sanding bit to make the groove wider. Choose a sanding bit which will allow the plane to fit into the groove. Also sand the 1/4" deeper end out so that it has extra room for the next part.
4. get your paperclip nad make it straight first. Now bend it around the rubberband (the one you glued to the propeller rotor earlier) and back onto itself. Now twist the two free ends together a bit and superglue it to the inside of the 1/4" deeper groove. Make it strong, glue it twice if you have to, but make sure you leave enough room for the plane to fit in behind it.
5. when that dries bend the paper clip into a hook or 90 degree angle. This is to bring it away from being too close to the shaft, you want the rubberband to stretch from the loop to the propeller without touching anything else.
6. Now just slide the dowel rod through the gray frame pieces you glued together earlier. It happens to be the perfect size to keep the gray pieces from sliing around on the rod.
7. When everything is dry you should be able to wind up the propeller and watch it spin when you let go. Use the silicone where the spinning rotor rubs against the gray frame pieces.
you can bend the paperclip to achieve this desired affect, you want the rubberband to be almost loose when it is not wound up at all.
now your porta-prop is done. To attach it to the plane, just push the plane up to the groove as close to the prop as possible. Take off the propeller and put a small doubled up ruberband over the shaft and plane to attach them better. Also, slide the main wing towards the tip of the plane, this will make up for the addition of the weight. your done have fun!