Wednesday, November 14, 2007

Status Report: Pump Plans

The blog has begun receiving requests for plans for the treadle pump from individuals and organizations.

The status of the CODEP treadle pump is that we have a prototype in the field in Haiti where it is being evaluated. Jim is traveling this week to Haiti and will be getting the results of a month of field trials. When he returns in a couple of weeks, we will incorporate any changes needed in the prototype and begin to create documentation for building one.

Jim and I are keeping contact information on file for those who have requested plans and will be in touch when we get our plans drawn up. Our experience has taught us that there are several subtle aspects to such a pump that need to have a great deal of attention; otherwise its' performance can greatly suffer. We want to fully document these hard learned lessons before we put out plans for people to follow. Readers are encouraged to keep up with our progress on this blog and feel free to contact us in the meantime for any reason. Jim and I thank you for your interest and we look forward to seeing this version of a treadle pump being built by many people, anywhere that there is a need.
Again, photo credit to April Leese.

Sunday, September 30, 2007

Pump Photos from April

The prototype pump has been in Haiti for some weeks now. Here you see Rick Land and a helper operating the pump on one of the first days there. This photo was provided by April Leese whose livejournal documenting her activities in Haiti can be seen at Readers are invited to stop over at April's to see what she's doing from time to time.

More of April's excellent photos of the first day of pump operation can be seen at

So, what's left to do? A lot. The pump is after all a prototype. Rick is using the pump, as are others, and Jim and I are receiving periodic updates as to what needs to change and what needs to be improved. Once we have the design more tuned than it is now, we intend to publish pump plans, and make them available to anyone. There is already talk under way about how to introduce the pump in Haiti, but that is still far from settled, and a much more difficult undertaking than designing the pump.

Tuesday, September 4, 2007

Pump Assembly On Site

Here we have Jenner, Winston, and Jobert standing in front of the disassembled pump. Winston is holding a photo of the assembled pump, I think. At Jenner's feet are the suction hose and 130 feet of garden hose that will be used to deliver water. Winston and his group hand carried the pump in it's suitcases and duffel bag through airports and customs.

In the second photo Winston provides instructions in the finer points of pump construction.

Next we see Jobert studying photos. Jim took photographs of the pump at each stage of disassembly. Viewed in reverse order, they form our instruction manual. That was the intent, anyway. Somewhere along the way, the guys hit a snag, and Kathy was called in to provide translations and what looks like a drawing. That's Rick in the right foreground.

Things are straightened out now, and the pump is almost finished. Jenner is installing a piston and it's seals into the cylinder. The last photo show Jobert and Jenner priming the now assembled pump by filling the cylinders with water.

Tomorrow, plans are to try the pump out at one of the project areas in the hills. Thanks to Kathy for the photos, and many thanks to Winston and his group for hauling the pump all the way from North Carolina.

The Pump is There and Assembled

I'm happy to be able to report that the pump was assembled Monday, and tested. That says that all the parts got there, nothing got lost, and those responsible for managing this have done a great job. Many thanks from Jim and me to all. It was reported that the pump when tested was estimated to produce ten gallons a minute. That's as it should be, for a low lift situation.

It's hoped that today, the pump will be moved to one of the project areas further up the mountains, and used there. We're also promised some photos, and I'll upload those and publish them as soon as they arrive.

Sunday, September 2, 2007

OT, sort of : Terraces and Vetiver Grass

This post is a little off topic, but this photo begs to be published. I've said this before, but readers should know that to enlarge photos for better viewing, they can click on the photo.

There are several points of interest. The first is the terrain itself. It's usually decscribed as mountainous. These aren't the rockies, but if you're carrying water or anything else on your back, or as is the custom there, on your head up these hillsides, they qualify as mountains. You'll also notice that there are no trees. The trees that used to cover these mountain sides have been cut and used for the most part to make charcoal. Much of Haiti's population, estimated to be as high as 8.7 million, uses charcoal to cook three meals a day. That's a lot of people demanding a lot of charcoal, in a small country, resulting in mountains denuded of any vegetation of any size. Haiti also enjoys periodic torrential rains as a result of passing tropical weather systems, ranging from tropical depressions to hurricanes. Over the years, these rains have carried away feet of topsoil, flushing it into the Caribbean Sea. One of the activities pursued by CODEP is erosion control in the form of terraces, or contour ditches. You can see one new terrace in the left foreground of the photo. The basin in the center of the terrace catches and conserves rain. The berm that forms the downhill lip of the terrace has been planted with Vetiver grass. This grass can form a dense hedge along the contours that hold and stabilize the soil, and filter the the rain water, preventing further erosion.

Photo Credit: Rick Land

Sunday, August 19, 2007

Going Somewhere?

Yes, we are. Or I should say the treadle pump is. After such good results from the testing described in the previous posts, it was decided that the pump is ready for field trials.

We've located a group going to the CODEP project (, in early September and they have agreed to take the disassembled pump as part of their luggage. A member of the group helped to number the parts and disassemble the pump so he'll know how to reassemble it when it gets to Haiti. As you can see, the pump and hoses are packed in three suitcases and a duffel bag. The only part that has to be made there is the mast, which is 60 inches long, and won't fit in the bag. We still have to collect a few parts and fittings, so there won't be problems attaching the pump to the hoses on site when it arrives. We also have to burn a CD with all the pictures Jim took during the disassembly process. So, the next post will hopefully show the treadle pump being reassembled and used in Haiti.
Update: I've received word that the suitcases made it through the various airport security checks, and customs in Haiti. So far, so good.

Tuesday, August 7, 2007

Pump Plumbing as of 8/6/07

In earlier posts both Jim and I have written that there were issues with the green vinyl suction plumbing that had been used to plumb the pump's valves. The plumbing worked just fine. The problem was that it was near impossible to install, and impossible to remove in order to maintain the check valves. The green hose was just too tight and inflexible for the fittings we have been using. We tried black poly pipe too, which was easier to install, but required additional fittings and hoses, because it was so rigid. This increased parts counts and costs. It was no easier to remove than the green vinyl.

Finally, we hit on ordinary automotive type rubber heater hose. It's flexible enough to install and remove easily, readily available, and cheap enough. The only problem is that it collapses under vacuum. This little conundrum was solved by making a coil out of galvanized 14 ga steel wire. Almost any wire of sufficient stiffness will do, even if it wants to rust. A wire coat hanger would work. The coil was made by winding the wire around a 3/4 inch steel rod. Again, what one uses for a mandrel is not critical. As long as the result fits inside the heater hose fairly closely, and prevents it from collapsing under the vacuum produced by operating the pump, it's all good. Only the hoses on the vacuum side of the pump need to have a coil installed.

We tested our cheap and dirty vacuum hose arrangement on 08/06/07. It works. We'll be posting the results of the testing later, probably with more videos. We're still looking for a cheaper substitute for the pretty stainless steel hose clamps we've been using to secure the hoses. They're kind of expensive. There are a number of possibilities, and as soon as we know what we're going to do, we'll post it here.

Saturday, August 4, 2007

Test of Treadle Pump to Longer Distance and Higher Elevation

With the success of pumping a distance of 160 feet at a height of 25 feet and with an improved strainer, we wanted to try for the maximum distance and height. We ran out of pipe long before we reached the pump’s limitations. The previous 160 feet run was with 1 inch Poly Pipe which was all that we had on hand. So we decided to extend it with standard ¾ inch garden hoses. By using all the hoses I had and borrowing some neighbor’s hoses, we came up with a total of 260 feet. Add to this the 10 feet of suction hose into the pond, we had a total of 270 feet. We also wanted as much height as possible, so we continued to run the pipe up a long hill. At the very end, in order to add more height, we threw a rope over the limb of a tree and hoisted it up an additional 30 feet over the height of the hill itself. To determine the total elevation, I waited until dusk so that my cheap laser level’s red dot could be seen and used it to shine onto lower trees. By making several steps down and measuring the distance from the dot to the base of each tree, then repeating several times, I was able to find the total elevation. The elevation of the end of the run as it was hoisted up to a tree limb was easy to find in that I simply measured the length of rope needed to hoist the pipe all up to the limb. The total was 60 feet from the surface of the pond to the open end of the garden hose in the tree.

We were expecting the pump to be much harder to operate with this increased length and elevation. Instead, it was about the same; just the strokes per minute were slower. It is not necessary to use leg muscles to force the treadles down. Your body weight provides the force. At the end of each stroke, you just have to raise your body weight high enough to step up on the other treadle. To accommodate people of different weights, one can just move their feet position further away from or closer to the pistons to change the mechanical advantage. We measured the volume of water per minute pumped and knowing the total lift, we could calculate the work required. Rate was 4 gallons per minute which is about 50 watts. According to several studies by others, this an easy output for people to maintain almost continuously. Larry operated the pump for 2 hours on a very hot day and was not excessively fatigued. Realizing that we probably weigh more than the average person who will be using this pump, we decided to add several additional inches to the treadle length to accommodate people that weigh less. We feel that except for some minor changes in the way we interconnect the piping so that it is more easily disassembled for cleaning, we have arrived at the final pump design. The following video is about 2 minutes long and shows the pump being tested at the stated pipe length and elevation. There is a short video following the first one that shows Larry operating the pump at this length and elevation after he has been at it for 2 hours. These test results were very encouraging. Our next step will be to get a prototype pump to our CODEP project in Haiti and begin creating drawings and instructions for how copies can be made by others.


Prior to the testing in the last video, all of our tests had been done using potable water. That's with no mud, and no sand or rocks. It occurred to us that when we started pumping pond water, we would need a strainer of some sort to keep such material out of the pump. Our check valves were designed so they would probably tolerate particles smaller than 1/8", allowing them to pass through. One of the first things we did with the new valves was to allow the pump to ingest a lot of sand. As expected, it clogged things up and required the disassembly of the pump to clear out the sand. What this taught us was that our Delrin ball check valves were as robust as we could expect, as they experienced no damage for the abuse they received, and that as expected, particles of sand or rock slightly larger than 1/8 " would jam the ball in the valve open. It also taught us that the green suction plumbing we were using had to be removed with a hacksaw. Not good. Plumbing changes are underway as I write.

The photo shows two of our homemade strainers. The thing at the bottom was an idea we abandoned. It's a lateral for a swimming pool sand filter. It most likely would have done a good job, but there aren't just lots of pool supply stores where this pump is going, and they're expensive.

The other two strainers are just pieces of PVC pipe. One was drilled with 1/8" holes and the other slotted with a bandsaw, although it could have been done with a hacksaw, or a carpenters coping saw just as well. Both strainers were tried, and both worked. The second photo shows what happened to the strainer with holes after a few minutes of pumping. The same particles that would have stopped the check valves clogged the strainer. What we finished with was a slotted strainer about twice as long as long as shown in the photo, to provide more slots and accordingly reduce restriction to flow. We pumped for two hours, with no appreciable clogging. There will be more on our test results with the next post, and another video.

Sunday, July 29, 2007

July 29, 2007 - Treadle Pump Test at Jim's 160 Feet Long and 25 Feet of Height

Update by Jim: On Saturday, July 21, Larry and I decided to bring the pump to my house where I have a pond that we could use as a source of water and a fairly long and steep hill to run pipe to simulate how the pump will be used in the CODEP project in Haiti. Some things we've learned: Saturating the piston-seal leather in melted paraffin did not work very well. The leather did not seal very well and there was a lot of friction as it rubbed on the cylinder wall. So far it appears that the best lubricant is Crisco; not the liquid vegetable oil but the solid product, much like old fashioned lard. We first set up the pump beside the pond and connected the output to 160 feet of 1 inch polypipe that was run up a hill for a distance of 160 feet and to an elevation of 25 feet. The following video shows a view from the exit end of the pipe looking downhill where Larry is operating the pump. Effort was quite easy and rate of flow was about 5 gallons per minute.

Video - 160 Feet Long/ 25 Feet of Height

Sunday, July 15, 2007

Latest Tests, Mixed Results, Mostly Good

Well, the pump described in the last post was hooked up and wrung out a few days ago, with mixed results. I have mosly good news though.

The new plumbing worked just fine, as did the new check valves. I was holding my breath about the new valves. The easy up-and-down mast worked too. The new plywood braces were plenty rigid. That leaves the paraffin valves. Results there were less than stellar. Without going too much into the gory details, the paraffin seals were almost impossible to prime, and once primed, the upper seals, the ones that should provide a seal on the vacuum stroke, were excessivly leaky, and wouldn't hold their prime. After a half hour fighting with the balky seals, I retreated to the older molded seals, primed the pump, and everything else worked.

Except the pulleys. The pulleys that hold the cable that raises the treadles on each vacuum stroke have been something we've sort of neglected till now. We were using a pair of old brass pulleys that I had lying about from an attempt to hang a bird feeder where the squirrels couldn't get at it. That endeavor failed by the way. Anyway, the pulleys were too small for the task we had applied them to, and they didn't survive. All the vigorous jumping up and down I did while trying to use the paraffin based seals didn't help any.

The pulleys have since been replaced with three inch diameter pressed steel pulleys with a ball bearing in the center, intended to help raise a garage door. If you click on the photo, you should be able to see the new pulleys and get a better look at the metal bails that hold the mast.

We still have a working pump. In fact, plans are to take the pump to Jim's house, plumb it to his pond, and try to pump the pond dry. No, really, we're going to take advantage of the water his pond can supply to work the pump for as many hours as he and I can make ourselves pump, so as to identify any part that is prone to premature failure. We're also going to play some games involving feeding the pump sand and mud to see how the seals and check valves handle that. We've got some strainers to test as well. Until now, we've been pumping clear water.

There's been some preliminary talk about shipping this pump to Haiti. Should all this testing we've planned work out with no big setbacks, I hope this can happen. The sooner the better. The sooner we can manage to get a pump on the ground in Haiti, the sooner we'll know what works, what doesn't and what needs to be changed.

Saturday, July 14, 2007

Treadle pump as of July 12

The pump has been rebuilt again. I think this is the fifth time. Fortunately, it's starting to look a lot more practical. At least I think so. This iteration incorporates some new features I have talked about in earlier posts, and some I haven't.

The seals, which are sticking out in front of the cylinders to dry are molded using melted paraffin. The pump cylinders have new homemade check valves. The valves are installed both on the same side of the cylinders, which allowed us to reduce the amount of plumbing required, and simplified the routing. The plywood braces have been cut down, to minimize weight and save materials. A cleat has been added on the left end of the pump, to act as a treadle stop, and keep the treadles from beating the plywood brace on the end of the pump to bits. A lot of the extra holes have diasappeared. We needed them earlier so we could change the position of things easily. The design has firmed up now to the point that those adjustments are not needed any more. One last feature that was Jim's idea was to mount the mast with metal loops that allow it to be raised and lowered without tools or any hardware. That's the mast lying across the top of the pump. If you look closely, you can see the metal bails that it slides through. The one on the left rotates with the mast to a vertical position, and allows the mast to slide down and seat on a bracket between the pump bases that you can't see, but is there. In the lowered position, the mast projects past the vertical supports and provides a carry handle on each end. How handy. More tests coming soon.

Redesigned Plumbing

Somewhere in an earlier post, I remarked that we were going to have to get the loopy green plumbing under control. We have. Instead of drilling the pump bases on opposite sides, we decided to drill and tap for the check valves on the same side of the pump, with the holes spaced 36 degrees apart. 36 degrees happened to be the magic number that placed the valves close enough together to fit inside the bases, but didn't cause them to interfere with each other when they were screwed in. Some geometry was involved. The photo shows the result on a partially assembled pump. I guess this is a good time to say that the pump has been torn completely to pieces and is being rebuilt from the ground up. That's one reason I've gotten a little behind in the blogging. Anyway, the result is greatly simplified plumbing. It's going to be quite a bit cheaper too, because there's a lot less of it, and because there are no short radius curves, so a cheaper type of tubing can be used it, even though I'm not using it in the photo. One thing at a time, please. The astute observer will also note that the new check valves have been installed. The new pump will incorporate a number of new features. Details later. Oh, I should also say that the 2x4 in the middle and the little pieces of plywood back by the pump cylinders won't be part of the finished pump. They're just there to get the spacing right.

Sunday, July 8, 2007

Shop Made Check Valves

For some time we've been operating the pump with commercially manufactured check valves. They work great, but they're expensive. One of the first posts here was about an attempt to make check valves for an early pump using standard PVC fittings, and kid's toy glass marbles. These did in fact work, but clearly we had to make improvements. We're also trying to keep the cost of the pump as low as possible, and four of the most expensive parts are the check valves. The problem was finding a source of some sort of sphere that would serve to replace the glass marbles. There are lots of companies that make all sorts of spheres, balls and bearings out of every material you can imagine, from the mundane to the exotic. They're also very happy to sell them to you, in lots of thousands. We needed eight or ten for our purposes. Fortunately, we were able to locate Salem Specialty Ball Co. in Canton, Connecticut. They were very helpful, and very accomodating to sell us Delrin balls in sizes and quantities that met our requirements, for a reasonable price. Thank you, Salem Specialty Ball Co., and special thanks to Deloris. In case you're wondering, Delrin is an acetal resin similar to nylon. It is said to have excellent abrasion resistance, which is important if you're trying to pump water that may carry considerable quantities of sand and mud, does not absorb water (it shouldn't swell), and is advertised as an excellent choice for check valves. It's also cheap in quantities, which we hope to be buying, if one day this pump is well accepted. So there. As usual, I've provided a photo showing four check valves ready to be installed, and some of what's inside. You can click on the photo to enlarge it and get a better look at what I'm talking about.
The valves are made from one 1 1/4" coupler and two 1 1/4" x 3/4" flush reducers. A 7/8" delrin ball fits nicely in the throat of one of the reducers, and stops flow in that direction. When flow reverses, the ball would travel back to the other reducer, and stop flow in that direction too, except that it's stopped by what I'm going to call a spider, which is what those two complicated looking star shaped objects are in the front of the photo. One is made out of aluminum, which I didn't like too much. The other is made out of a piece of the PVC that both spiders are sitting on. The PVC came from a short section of PVC pipe that was slit down one side, and heated in a 300 degree oven for about five minutes. At that temperature, PVC is as pliable as putty, and can be flattened between two boards and held till it cools. After that, it can be cut, filed and drilled. The spiders look complicated to make, but they're not. You cut a square the right size, and drill a half inch hole in the center. Then you use a half round bastard file such as you see in the photo to file the half round recesses in the four sides of your PVC square. It's easy, and it only takes a few minutes. To the left you see a Delrin ball sitting on it's spider, inside a spacer cut from a piece of pipe to provide space in the valve for the ball to travel back and forth, and retain the spider. The second photo shows a cut away copy of the valve so readers can see how all this goes together inside. In quantities, the cost of this valve should be less than three dollars each. I'll let you know how they work as soon as I can get them installed in the pump.

Paraffin Molded Seals

Early on in this project, while we were studying treadle pumps in general, and leather seals in particular, we ran across several references to making seals by soaking leather in melted paraffin(candle wax) and pressing the still hot leather into a mold. In an earlier post I wrote about making molded seals using the pump pistons and a section of PVC pipe after soaking the leather in warm water. Since then we've made molds for making paraffin seals, which you can see in the first photo.

The base and and piston are made out of old countertop material. They could be made out of anything, even wood. The rings are short sections of the same four inch PVC pipe that's being used for the pump pistons. There's a large 45 degree bevel at the top of the rings to help ease the leather into the mold without tearing it up. Today, I finally got around to molding seals. Five inch diameter leather circles were soaked in melted paraffin, and placed in the molds. The bolt through the center of the mold was used to tighten down on the leather and force it into the mold. It worked like a charm. The only problem was that I made the rings a little too short. I improvised by taping the rings together with masking tape, and using one mold at a time. I'll make taller rings later. The second photo shows one of the seals out of the mold, and one of the seals still wrapped around the piston, waiting to be trimmed. I trimmed the edges of the seals with the razor knife to the left, using the top of the piston as a guide. I have no idea how well these will work. We've read that these seals will be self lubricating, and less prone to rot and swell from absorbing water. We'll try these seals the next time we take the pump out for a walk, along with the new check valves we made today. That's what the next post is about.

Pump Video as of June 23

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.

Wednesday, May 9, 2007

Pump Video, Second version

New Seals, New Pump

Since the last video, there has been an improvement in the pump seals. The original piston was machined to squeeze the leather seals against the cylinder walls to make them seal. This worked, but the result was high operating force to move the pump handle. This was improved by making a new piston machined to a close fit to the cylinder wall. The original pistons were turned down to allow the leather seal a much looser fit between the cylinder wall and what are now just seal retainers. Differential pressure between the inside of the seals and the outside of the seals act to force the seals against the cylinder walls to seal in the water, while allowing the seals to flex to accommodate the irregularities in the cylinder walls. The result is a seal that follows the cylinder wall, seals in the water, and requires much less force to move the piston. This afternoon I built a new pump, with the new type seals, check valves installed directly in the bottom of the pump cylinder, and a handle so I could move the pump up and down without tearing my hands up on the piston rod. Then I got my fit young son to operate the pump while I made the video in the next post. As you can see, things are much improved, and we have a good enough pump to use to make some measurements so that calculations can be made to further the design of a treadle pump. Good progress for a day's work.

Monday, May 7, 2007

Experimental Pump Video

Check Valves

We made a pair of check valves from standard PVC plumbing fittings available at a local hardware store. The fitting in my hand is a 3/4" solvent to 1/2" pipe thread reducer. The check ball is a glass marble. The check ball was caged by cross drilling a piece of 3/4 " PVC pipe and installing two pieces of welding rod. In actual practice, a ball bearing would be used in place of the marble, but one the right size wasn't available. This contraption was pressed together, and we had a check valve. The valves were assembled with a tee to our test piston and cylinder, as you can see in the second photo. The next post will show a short video of our made-in-a-day hand pump in operation. The results were encouraging. The voice you hear in the video is my wife who obviously isn't comfortable operating the camera, and is a little confused about the recent goings on in the back yard. Understandably so.

Sunday, May 6, 2007

Cylinders, Pistons and Seals

In the introduction, I said that treadle pumps needed cylinders and valves. They also must have pistons,and seals to keep the water from leaking out around the pistons and the cylinder walls. One of the things we are trying to do is to find a way to make these pumps without having to have a full blown machine shop, using materials available in Haiti. Early on it was decided to try to fabricate as much of the pump from PVC and standard plumbing parts as possible.

What you see is an experiment with using leather washers to make a piston seal. Two washers were used, one to seal against vacuum, the other to seal against pressure. The cylinder is a piece of 2" PVC pipe, with a cap on the end. The cap was drilled and tapped for a ball valve so that I could vary the resistance to flow. Long story short, the seals worked, surprisingly well. The addition of vegetable shortening to the leather improved the seal, and greatly reduced resistance to motion.

The results of the piston seal experiment was encouraging enough that a search for check valves was begun.


The purpose of this blog is to document the development of a treadle type irrigation pump. Our efforts to accomplish this are currently funded by the Haiti Fund Inc.

So, you may be asking, what's a treadle pump? It's a foot powered water pump used for irrigation. It usully has two pedals, called treadles, that the pump operator stands on and operates with a walking motion. These treadles are connected to two cylinders with valves at the bottom that comprise a pump. There are two basic types of treadle pumps, lift pumps, and pressure pumps. Lift pumps have a practical limit to the distance they can lift water of seven or maybe eight meters. In Haiti, crops are grown on terraces at greater distances above the water source than that, so a pressure type pump is what's required, and that's what we're trying to design and build.