Wind-driven whirligigs are simple machines that take wind energy and transfer it into propeller movement. Whirligig propeller hubs have to be wide enough to hold the propellers in place perpendicular to the shaft. They must be securely attached to the shaft to prevent wobbling. Balance is the main objective when designing whirligigs. Being at the center, the hub needs to be cut so that it will ensure stability in the whirligig operation.
Cut a hardwood hub measuring 4-inches by 4-inches and 1-inch in thickness.
Draw 2 lines across the center and at right angles to each other, on one face of this wooden piece.
Carry these lines around the edge of the hub and saw them at a 45 degree angle. Make them 1 inch deep. The whirligig blades will go in these slotted spaces.
More propeller slots can be added at equal intervals between the original two lines.