This a simple worm gear mechanism. It requires a 6mm wide rod for the axle and a 608 ball bearing for the gear. The model could be easilly adapted to use differently sized ball bearings or rods.
The worm gear itself is a bit tricky to print, it requires a small layer height and needs to be printed in upright position. Supports are necessary but should be pretty easy to remove.
Assembling should be pretty straightforward. It is best to first glue the handle to the end of the rod used as axle, fill the inside of the worm gear with a bit of glue, put it into place on the base plate and push the axle through. The regular gear should be glued to a 608 ball bearing which should be glued to the base plate.
Most parts were designed in blender. The worm gear was created using a screw modifier and the regular gear using the extra objects addon. The teeth of the regular gear are a bit askew to compensate for skewness of the worm gear.