Sunday, June 24, 2007
Thursday, June 21, 2007
To make the seals I first marked five inch circles on the leather using an ordinary compass. The circles were cut out with a sharp knife, and a 3/8 inch hole cut in the center. The leather circles were then soaked in warm water for about half an hour. I used the pump pistons and seal retainers to hold the seals, and forced them into two short sections of four inch PVC pipe of the type we're using for the cylinders. The first photo shows the seals in the molds. The edges of earlier seals were convoluted, or accordian shaped. This leather is much more pliable than what we've been using, and I was able to smooth out the humps and bumps using my fingers.
In the background of the second photo (click on the photos to enlarge them for better viewing) you can see a piece of the leather that I used, and the short sections of PVC that were used for molds. In the foreground are two of the now cup shaped seals , dried and with their edges trimmed, more or less. In the middle are the two pistons. One has the new seals installed, and the other is positioned to show as best I can the piston and seal retainers. The piston is machined to a close fit to the cylinder. The retainers are quite a bit smaller than the piston, with generously radiused edges. Their purpose is to loosely hold the leather seals without forcing them against the walls of the cylinder. Pressure or vacuum in the cylinders formed as the pump operates forces the seals against the cylinder walls. If all goes well, tomorrow we'll try another version of the pump, with these very seals.
Sunday, June 17, 2007
Saturday, June 16, 2007
Wednesday, June 13, 2007
Wednesday, June 6, 2007
In the last post I promised another treadle pump with three inch pistons. Here it is. If you compare it with the first version, you'll see the cylinders are larger in diameter, shorter, and installed at a different location in the treadle frame. The treadles and treadle stops are lower too. The purpose for locating the pumps where you see them was to provide greater mechanical advantage to the operator. The pump works great. The larger piston diameters required the mechanical advantage we built in this time as expected. This time I talked my wife into acting as one of our test subjects. One of our concerns is that people shorter and lighter than Jim and I must be able to operate the pump. My wife fits the small size requirements, and she had no problem moving water to a height of 25+ feet.
The second photo shows one of the three inch pistons. The commercially manufactured check valves can be plainly seen. The pumps are mounted to the treadle bases with short sections of all thread rod secured under the bases with "t" nuts and passed thorough plywood donuts made to closely fit the outside diameter of the cylinders. Nuts and washers tighten down the donuts against the pump bases and hold everything secure and upright.
Last time we were too busy and disorganized to make videos. This time, due to popular demand, we have videos to post, which I will do as soon as I can get them uploaded.