My first attempt was simply boxes rotated around a central point. multiplying both the length of the box, and the number of boxes by the same amount to produce compatible number of teeth. These teeth jammed far too oftain, i believe due to the sharp corners.
on the suggestion that more rounded gear teeth would be in order, i took this to the extreme with cylinders, added and subtracted from the outer edge of a large disk. again, i multiplied the radius of my disk and number of surrounding cylinders to achieve compatible gears.
In an attempt to keep the fan from flying off prematurely, i created gears with a slant to the teeth, in hopes that it would pull the blade back on while power was applied, but allow it to freely fly off once power ceased.
gears get slightly sideways(will need to add guides, especially to gear with handle at bottom)
gears want to move apart(will need to add some sort of keeper at top of shaft)
gears hit each other(will need to lengthen smaller gears in relation to larger gears, or add some other method of spacer)
fan hits top of opposing shaft(will need to adjust shaft lengths to match gear heights)
fan will not fly(will need to redesign fan for greater lift, less weight)