Here is the final redesign of the wind pump including many of the suggestions made by readers (thank you!). Let's see if I can list them: * Substitute...
Step 5: PVC Water Pump
Here is the drawing of the PVC water pump gun I made for my visitors. I made no changes except to add an eye hook to the top of the piston and secure the second ball bearing to the hook.
And here also is the video of how I put it together.