Questions on ram pumps

Hey all, I know several of you guys have made ram pumps before, so I thought I would see if I could get some input. I ordered parts to tie into my hydro penstock, which is usually shut down in the summer due to lack of water (I have not measured the flow yet, but it is quite a lot, just not enough to generate much power).

Here is the basic layout

I might have slightly more than 8 feet of head, should I use as much as possible, or will the pressure get too high if I overdo it? Also, since the penstock is closed for a long distance back up to the source, I am thinking I will need a standpipe to help the shock wave dissipate at the top of my 2" drive pipe?

I have started laying out my pump body, which is made of 1-1/2" iron pipe;


I made a custom T at the far left, onto which I will be affixing the waste valve. This is my thought for that (forgive the crude MS-Paint CAD drawing )

Basically there will be a restriction that the valve plate can shut against, and then in the upper section I will mount an inch of bushing to guide the shaft. How much clearance do you think I should leave around the edges of the plate? Should there be enough travel for the plate to drop all the way down into the perpendicular section? I will probably drill some holes so the water above the waste valve can drain out, but I have head some people say that water above the valve helps to make it self-priming by adding a little weight temporarily. I am thinking the shaft will be all-thread, so I can easily adjust the travel length and also add some weights to dial in the waste valve cycle.

I made my check valve out of 1/4 rubber sheet I had from another project.

The threaded end on the right of the pump body will go into a T, where I will connect the expansion tank, and a reduced down drive pipe. Inside the pressure vessel (old fire extinguisher) I put several sections of closed cell foam from some pipe insulation.

I will probably also include some robust mounting feet to bolt it down to a little concrete pad. Does anyone have any input before I start welding? I am hoping it will come together with a minimum of bought parts. I need to get going too, as summer has finally arrived, and it will be time to start irrigating soon!

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After assembling everything, it dawned on me that the height of my T adds quite a bit of travel to the waste valve. I am not really sure how much water will flow until the flap drops down into the perpendicular pipe:

That means the flap needs to be raised like an inch and a half to get it to seal against the restriction.

I am not sure if that is too long of a stroke or not, or if I will be able to fine-tune the travel distance and weight to get a good frequency. I have heard people say anything from 60-150hz is what I am aiming for.

I guess now I need to get some pipe and actually test it out!

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Many years ago I picked this up in Mexico city.

The rest coming in the following message.

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Sure enough, the first attempt was not a success. Here is the assembled pump:


I did get the penstock set up, and it seems to be working well. I decided to just add a valve to my 4" pipe and fill a tub at the top of the hill. I think I have almost 10 feet of head. When I open the valve at the top I get a torrent of water, which filled a 6 gallon bucket in about 6 seconds. I am not sure it could keep up that flow rate, but I will easily have 15 gpm, which is as much as I think my 1-1/2" pump will be able to use.

It was a nice sunny day, so I did spend some time just playing with it, and if I kept pushing the plunger down it would pump. I got it up to 21psi, and there was a tiny bit of water at the the outlet. There is just way too much travel, so the plunger goes to the top and just stays there. If I had several pounds of washers, it might have worked… I think I am going to take it back up to the shop, chop down the height, and switch it to a spring-loaded waste valve like the one above.

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One thing to consider aside from excessive travel of the plunger: when the it goes to the top and stays there, it is (in part) being held there by pressure against it. In other words, the head pressure from water in the drive pipe doesn’t let the plunger drop.

Immediately after a power stroke, when the check valve closes, a water hammer pressure wave is reflected back up the drive pipe. When it dissipates, there is a moment of equal pressure on both sides of that waste valve plunger and it should fall at that time. If for some reason, that moment of equilibrium is too short, or the weights atop are too light (etc), the plunger won’t drop. However, you can cheat and give it a fighting chance by considering the use of a riser open to atmosphere in the drive pipe (a place for the pressure wave to go) and/or by increasing weight.

I think I made a few posts and pasted some links on this subject in kristjanL’s homestead thread.

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Okay, I gave the waste valve another go. The Mexican design was super easy to make, and was really easy to adjust the tension to get it running on its own.

Here is my current setup.


The sandbags do a pretty lousy job of securing the pump, so it tries to jump around a bit with each stroke.

At the top of the hill I have a tub, and you can feel the pulses come flying up the pipe and dissipate.

Here is the outlet.


I am only pumping about a gallon every 3 minutes, so it should move about 480 gallons per day. I estimated that I was putting something like 6-10 gpm into my tub, so my efficiency is not good.

I added a rubber gasket to my waste valve after the first picture was taken, but it seems it was too small. The edges are not staying flat, so the seal it makes with each stroke is not very tight. Edit: Rewatching the video I can hear it hiss after each “clunk,” which is probably the sound of the water I should be pumping escaping out the gasket. I am hoping that between fixing that and casting a heavy base to bolt it to, I can squeeze a little more flow out of it. I took a short video of it running, I will post it in a few.

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Got to love a simple machine doing real work. There is another variable, the pressure vessel, it would be interesting to see how that influences performance, I would think a larger vessel will slow down the stroke rate, but maybe increase the efficiency at low head?

The valve sealing should improve performance.

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There is also an issue of friction and water surface tension in that equation.

Amen Garry. I think you are right about the bladder tank.
Also, that manual you posted is excellent. I really like that series of pamphlets. I have used a couple of them. There is a whole series, I wish I could find a complete set.

Looking great Carl.

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