This instructable describes the construction of a simple solar thermal motor, made from commonly available, low cost materials.
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
The following is a list of the materials you will need:
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)