Gate Plastic
The gate for the valve is made from 1 inch thick HDPE or Polypro, or other plastic of your choice. It should be a resin that can withstand sunlight since it will be used outdoors. The gate is 13 inches wide and about 16 inches tall, in order to fully cover the opening in the flat plastic plate when closed. Slots are milled in each side as shown. I used 5/16 wide slots, 1/2 inch deep to slide on the 1/4 thick angle iron without binding. Note that the slots are angled 1 degree relative to the front surface of the gate so that when it slides upward on the angle iron, it also moves away from the flat sheet as it opens. This prevents binding, and when closed it pushes the gate close to the plate. Note that in the exploded view there is a spacer also tapered by 1 degree that fits between the angle iron and the flat plate. This combination results in the gate moving parallel to the flat plate as it moves away when opening the valve. There is a groove machined into the non-sealing surface of the gate that I filled with black paint. This line is approximately through the center of the circular radius on the bottom of the gate, and helps with calibration of the water flow as explained on the photo of the assembled valve. Additional holes shown in the part are for mounting the lead-screw attaching block and wedges described in the photo of the valve.
