If you look closely at the vertical gear mechanism, you'll see a small red ball bearing on the back side of one of the gear "teeth." This bearing, and another identical one attached to the piston on the water pump are what allow the connecting piece between the windmill and the water pump to move freely, transferring the wind's horizontal force into the up-and-down force of the water pump. The connecting "rod" itself is made out of PVC. I painted it to look rusty (see step 4
in the the outdoor chandelier project for details), and later inserted some bicycle spoke nuts into the plastic by heating them over a gas stove.