The original listing for this fan over promised and under delivered, "you can actually use it to cool down!". https://www.thingiverse.com/thing:4901910 We think it is mostly useless, but we tried to make it slightly less crappy by fixing a few things.

If you have a printer that prints the original gears accurately to the designed dimensions, then you will have loose sloppy fitting gears. These will slip and not work when you pump the handle. We reduced the id of the gear bores to leave around 1/2mm clearance. If it is too tight then friction will slow the gears while turning.

We recommend using 4mm pan head screws to hold the handle to together. This is secure and allows you to disassemble to fix the gears if needed.

We modified a fan with different blade to replace the original version. http://www.thingiverse.com/thing:2267855 This wasn’t any better, if possible the new fan design is actually worse.

I think the real problem is getting the fan to spin faster. The improved gears and metal screws helped more than changing the fan design. There may be a better fan design, but is it worth the trouble of experimenting?

Finally we drilled a small hole through the fan into the drive shaft. We added a self tapping screw to hold these two parts together. This doesn’t fix the air blowing, but at least the fan doesn’t randomly fall off.

At the end of the day, you still have a crappy fan, but what if you were not building a fan. Imagine you just built a hand exercise device like one of those old time gripper tools, see our last photo. Each time you squeeze the handle you are really building up hand strength. Any air circulation is just an added bonus.

Tips on How to Operate

First push the fan to get it spinning. I like to have it go clockwise, but you can try both directions and decide for yourself. As it spins, the gears rotate and the linkage arm to the handle will move out. Just as it goes past the max. you squeeze the handle in and speed up the rotation of the gear. Each time it rotates back around you time the next squeeze to keep the rotation going. If you squeeze too soon you can stop the fan, it is all about timing the next squeeze for maximum spin.