Sunday, June 24, 2007

Treadle Pump as of June 23

Today we tested what I'm going to call our first prototype pump, with the new molded leather seals I described earlier. If you've been watching, the first thing you notice is that the pump has grown quite a bit shorter. That's a good thing. The operator can now climb up on the pump without getting altitude sickness. The vertical supports for the treadle and the mast are now trimmed down to seventeen inches high. The pistons are shorter as well. The mast now has one crosspiece instead of two, and the nylon rope we used earlier has been replaced with steel cable. We decided we were wasting a lot of energy stretching the rope. There's little stretch now with the cable, and better performance as you might imagine. The new molded leather seals worked just great. They provided a superior seal compared to earlier seals, and did not lose their shape as I had feared when they got wet again. The pump is quite a bit lighter too with much of the unnecessary wood trimmed away. The reason you still see a lot of holes that don't need to be there is that we're reusing the wood from the earlier test frame. So, today was another good day. We still have a lot to do before the pump is ready to ship. We have to make it lighter, and easier to build, with fewer materials. We have to decide what to do about the check valves, which are the most expensive parts of the pump. At this point, the giant green loopy plumbing you see can also be reduced in size as well.

Thursday, June 21, 2007

More About Leather Seals

Until now, we've been using leather that was on hand, left over from other projects, to make our pump seals. About a week ago I went to a local Tandy leather store. I explained to the gentleman running the store what I was trying to accomplish, and he showed me the type of leather that he felt would better serve to make seals. This post is about our first attempt at making seals using the new leather. I've also received a comment, which was really a question, about how we make our seals. I'm going to try here to illustrate what we're doing and how the pistons, seals and seal retainers go together.

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

New co-author

I've been in the background since the beginning of the idea of designing a treadle pump suitable for Haiti Fund, Inc.'s project in Haiti. I've finally achieved status of co-author on this blog and you will see a new link to my contact information that has been added. Thanks for your interest as the design evolves. Jim S.

Treadle Pump video, Four Inch Pistons

Saturday, June 16, 2007

Testing is Done.

Today, we tested our four inch cylinders and pistons. We were concerned that the forces required to lift water 28 feet would be too great with four inch pistons for a smaller (100 lb.) person to manage. It turns out that it is workable as long as the pump provides enough mechanical advantage. What happens is that the smaller person just has to move down the treadle towards the mast and away from the pumps. When they do so, and take the same size steps at the new location, the pistons travel a shorter distance in the cylinders, and the pump just moves less water. It means that a smaller person can still lift the water as high, just not as much water as fast. It makes sense if you think about it. We also learned a number of other interesting things as well. For example, it's much more comfortable to operate the pump if you're facing away from the pistons than if you're facing towards them. As the treadle travels downwards, if you're facing away, your toes point downhill. Turned the other way, you find yourself standing on your toes, with your calf muscles under strain, which causes fatigue very quickly. It's also very helpful to have an adjustable stop for downward treadle travel to accomodate different sized people. If there is a solid stop at the bottom of the treadle's travel, it's much easier to keep your balance and actually have a little rest at the bottom of each step. That's the reason for the steel rod you see sticking out of the right hand side of the treadle frame in the photo. It was our quick and easy adjustable treadle stop.
I should also say somewhere that this pump moves a lot more water without much more effort.
So, what has to happen next is that we have to disassemble our frame, and cut away everything that doesn't have to be there, and make some of the parts more durable and rigid.
The frame will probably shrink in height by about seven inches, which is good from the users standpoint. The cylinders and connecting rods will also be shortened by about three inches. Oh, yes, we have another video which will follow as soon as we can upload and link. Stay tuned.

Wednesday, June 13, 2007

Four Inch Pistons

After our last pump was built and tested and videos had been made, Jim and I put our heads together and after much thought and discussion it was agreed that four comes after three. So, we have built four inch pumps as you can see. Actually, the idea is to see if the forces involved with lifting water to a height of 25 feet with four inch pumps are greater than a 100 pound person can manage. The new pumps will be installed in the treadle frames shortly. We'll see how they work, and how hard it is to pump what we hope will be still larger quantities of water to the top of my rain gutter. I promise another video so you can see as well. The photo also shows the pistons and leather seals. One set has already been formed. The other is still just as it was cut.

Wednesday, June 6, 2007

Treadle Pump Video, Part 3

Treadle Pump Video, Part 2

Treadle Pump Video, Part 1

Second Treadle Pump, Three Inch Pistons.

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.

Tuesday, June 5, 2007

Friday, June 1, 2007

Our First Treadle Pump

The results of the 2" hand operated pump were encouraging enough that the decision was made to build a foot operated treadle pump with two inch cylinders, and an eighteen inch stroke. The long stroke was chosen to enable the pump to move about a quart of water with each foot stroke. This time commercially maunfactured check valves were used. The first photo shows the cylinders with their check valves, and one of the pistons and piston rod. The check valves were installed by boring a hole directly into the side of the PVC cylinder cap, and tapping the hole for a 3/4" pipe fitting. It works just fine.

The frame of the treadle is made of wood. Yes, I know, it's a tall overbuilt monstrosity. It's been made so that it will accomodate cylinders up to four inches in diameter, with strokes of up to eighteen inches. It can also be easily changed to provide different locations for the treadles, pumps and the pulley support mast so we can experiment different configurations that provide different mechanical advantage to the user. That's the reason for all the holes you see in the verticle supports in the third photo. So, think of it as a test fixture that will allow us to determine the best configuration for the finished design, and it won't look so ugly. We had to start somewhere. The good news is that this thing pumps water. Lots of water, to a head of 25 feet, with little effort. We spent the better part of the afternoon pumping water, changing the stroke, and moving up and down the treadles to try to determine the practicle limits of foot stroke length before fatigue and discomfort set in. In other words, a human can only step so high for so long before he gets tired and sore. We're trying to design so as to minimize discomfort and delay the onset of fatigue for as long as possible for the user.

We collected a lot a of data which has to be number- crunched. That's Jim's department. My department is building three inch pump cylinders for the next step in the design. I don't have a video to post this time. There was just too much going on this day. I'll promise one the next time we have the pump up and running with three inch cylinders.