Solar Thermal Motor

Step 4 Makeing the cylinder 1

Measure the diameter of one of the Styrofoam cups, and use your compass to draw an equal-sized circle on the freezer tray. You can trace the circle directly off the cup, but it will make it difficult to locate the center of the circle, which you will need to do.
Cut out the circle, and make a hole the size of your dowel at it's center.
I used my glue gun to melt the hole.