Curved Spoke Flywheel
I found the instructions for this wagon wheel in a woodworking book for boys, if made from metal with a hub it would make an excellent flywheel.
The drawing is done with a compass, the measurements given are for a 3 1/2" diameter wheel. These are basic instructions and simple enough that they could be cut by hand with a jewellers saw and cleaned up with a file. If you have a lathe and milling machine quite an elaborate flywheel could be made.
To divide a circle in thirds.
The sides of a hexagon inside a circle are equal to the radius AB, with your compass set at the length of the radius strike six arcs around the circumference.
Draw a line from every second arc to the center of the circle.