This device operates by harnessing the ability of certain polymers (in the case black plastic bags) to shrink when exposed to heat, and relax back to their original length when cooled.
Normally, this shrinkage occurs in all directions within the material. However, the material can be stretched, causing its polymer strands to line-up, and directionalizing the shrinkage.
The solar thermal motor operates by using bands of stretched black plastic bag to continually pull a flywheel off-center as it rotates on an axle. The strips are heated by sunlight on one side of a drum/flywheel assembly, pulling the flywheel toward the sun-side. As the strips rotate to the back, they cool in the shadow of the drum and relax. This makes the flywheel continuously off-center on the sun side, causing it to rotate.
Step 1: Tools and Materials
1x Black plastic trash bag
2x Styrofoam cups
1x 1/8" wooden dowel 12" long
1x Styrofoam freezer tray
2x Sewing pins (Forgot these in picture)
1x Plastic yogurt (or similar) lid approx. 4" dia.
1x Scotch tape
2x Tin cans
-Single edged razor or xacto knife
-Felt tip marker
-Ruler (forgot this in picture)
Step 2: Cutting Bag
You will probably need about 10-15 bag length strips, but it depends on how careful you are at stretching the material in the next step.
Cut each bag length strip into 8-12 inch sections.