Pumps Guide - SuperPiston MK I and MK II

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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HBWW
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Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Apr 15, 2013 5:05 pm

UPDATE: Obsolete information redacted/struck out. Outdated images have a red subtitle. Added a tips and flaws section to the bottom.

Homemade pumps. Two words that can make anyone cringe with horror stories of pump designs failing; pumps that leak/squirt or simply don't seal and cause massive problems.

After I've gone through homemades pump hell myself, I have come across the right way to build them. The key is all in the O-ring socket, which must be perfectly straight, and must be sturdy, or it will not work. Expanding wooden dowels don't do the trick, tape doesn't do the trick, and epoxy alone doesn't either. In addition, my design doesn't require any special precision tools to file/grind out any grooves, as we all know that doing so by hand doesn't work half the time. (It's also annoying and tedious to do.) You need every part of the pump seal to be made with precision, not cut by hand. Sure, those nice skirt seals used in stock blasters would be ideal, but until we can find a viable supplier in the U.S. for them, they're not a real option. (Short of buying cheap piston pumper knockoff blasters everytime you need a new pump, but you end up with a LOT of scrap parts, assuming the blasters' pump seals are even the right size.) So with that said, I present a full guide on pumps, all from scratch. The SuperPiston is very customizable and uses durable parts, although there's a few weak points in the design that I'm working to resolve but have not found any truly alluring solutions to yet.

This guide does not cover the rest of the homemade blaster, only the pump. This design in particular is for 1/2" sch 40 pipe; if you want a larger pump, you will have to figure something out, adapt this design with different components, and/or wait for me to come up with a solution for 3/4". This guide is for the MK II, but the MK I will be explained in the end.

Tools Required or Recommended:
- Hacksaw
- Drill
- Epoxy (The kind that works with stainless steel and aluminum; I use Devcon's Plastic Welder.)
- Epoxy Putty (It seems that any putty will do, but obviously steel ones are the best)
- Duct Tape (Optional; May actually be a bad idea; see rest of guide)
- Silicone Grease

Keep in mind that the pump consists of the following components: Seal assembly, Seal, Rod, Stopper, Cap, and Handle.

Parts:
- 1/2" Hollow Aluminum Rod (I can find these at Lowe's. You may be able to substitute this component with something from McMaster, but be absolutely sure that the OD does NOT go past 1/2"!)
- 3/8" ID 5/8" OD O-ring (I got mine at McMaster Carr, but they should be available at any hardware store. Your Sch. 40 pipe's ID will vary, so check. Ideally you'll want looser pipe ID.)
- 1/2" Sch. 40 PVC (This is the pump shaft. As mentioned, check the ID of the pipe for something looser. Looser pipes may need 2 O-rings, tighter pipes should have only 1. You can substitute this component with Sch. 40 1/2" clear PVC [can be found at McMaster], if you want some class.)
- 3/8" Socket Head Screw, Stainless (This component is key to the whole pump design. Length does not precisely matter as long as there's enough to go into the dowel for the epoxy to hold it in place, but make note of the differences in where the threads end near the head of the screw. Must be stainless steel for obvious reasons, although if you find one that's some type of plastic, it should work too.)
- Nylon Spacer; I used .375" ID, .562" OD, 1/2" Length. The spacer should be long enough to be stable on the socket head screw, but should still be short as possible. The ID must fit well on the socket screw (keep in mind that the threads complicate things and you won't really need an exact ID value, although a snug fit is best) and the OD must be enough so that it can hold the O-ring on while still fitting into the PVC pipe pump shaft. Do not use this component as it will result in leaking. Instead, make sure your aluminum rod is cut well, with a square end. I kept this for reference purposes, so just ignore it.
- Spacer/Stopper: You do not want to use the seal itself as the stopper, or disaster may happen. Make an additional one yourself along the rod. I used duct tape rolled up, but this seems to be making the water all nasty-colored. Epoxy putty would work well, but bear in mind that it will have to be grinded (with a Dremel or with sandpaper) if you carelessly make the spacer too large so that it doesn't fit in the pipe.
- 1/2" Endcap: The classic homemade pump cap. Alternatively, you can attempt a 1/2" male adapter and 1/2" threaded endcap, but I haven't tried this and can't vouch for it. Never, ever solvent weld any pump caps/adapters to the end of the pipe or you'll very likely regret it later. (And will likely need a hacksaw to fix problems.) This endcap requires a 1/2" hole drilled in the center and goes on the rod between the handle and seal.
- Handle. Do whatever you want here as long as the handle can stop the pump from going in too far. (You will need to measure things out and make sure of that.) One of my pumps simply uses duct tape wrappings, but if you want something more elegant, you can use PVC pipe, nuts and bolts, and drilled holes. See pictures, be creative too!

Assembly:
- Place O-ring(s) on the socket head screw; move it to the end until its flush with the screw head.
- Cut aluminum dowel to length as needed for your pump.
- Go to the end of the dowel that's cut straight. Unless you're able to cut it perfectly straight, used the end that was cut before it made it to the store shelves. (You may want to buy shorter lengths if possible for this.)
- Put epoxy on the exposed end of the screw, as well as on the opening of the rod. Place the seal assembly in, rotating as you go to spread the epoxy.
- Make sure the seal assembly is as centered and straight as possible with the rod! If the end of the rod you're using is cut perfectly, you shouldn't have to worry about this much or at all. On the other hand, if the cut is rough, sandpaper (or grind with Dremel) until its straight as possible, and use care when epoxying to ensure the seal assembly stays straight with the rod.
- Wait for epoxy to cure. I'd give at least 24 hours to be safe no matter what epoxy it is.
- Build/assemble/place the stopper on the rod itself, near the seal.
- Drill the 1/2" endcap, place on the dowel.
- Assemble/build your handle.
- Make sure the open end of the pump shaft is easy to insert the new pump into. File/sand the inner edge of it to create a curve. Apply some silicone grease (not too much) to the O-ring before inserting. (That's what she said.)

Pictures!

Hardware store socket head screws (stainless steel):
1.jpg
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Hardware store nylon spacers:
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MK II seal assembly parts:
3.jpg
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MK II seal assembly put together (no epoxy yet) Do not use the nylon spacer pictured, just use the O-ring and place the seal assembly all the way in. Adding the nylon spacer will result in a leaky pump.
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MK I seal assembly parts (and shows why stainless steel is needed; don't use the crappy, rusting screw depicted) next to PVC and duct tape handles, and drilled endcap:
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MK I seal fully assembled including epoxy (and this one uses the proper stainless steel screw) next to a failed epoxy putty O-ring holder experiment:
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PVC handle (obviously needs shorter screws):
7.jpg
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Unrelated, a disassembleable component on my homemade piston pumper that, when detached, makes a great war horn thanks to the check valve:
8.jpg
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High resolution photos in a zip:
http://www.mediafire.com/?r5bljozhouceccl

Happy building. Also, any feedback on how to improve this guide and/or the pump design is welcome. I may try to push this off to HBWW's Workshop homemades section later if I have time.

Tips:
- Make your pump removable! Before the pump attaches to the rest of the homemade, add a threaded adapter and set up your homemade so that it can be detatched. I attached the other end of the pump shaft to a 1/2" male adapter that goes directly into a threaded tee.
- Use an internal pump rod stopper! I was able to find a screen that works very well as a stopper (which I placed between the pump shaft pipe and the 1/2" male adapter when solvent welding them) to ensure nothing gets stuck too far, should the seal assembly detach somehow.
- After epoxying the seal assembly to the pump rod, you can remove the seal assembly using an appropriately sized allen wrench (if using the socket head screw I suggested). Rotate counterclockwise to unthread it from the epoxy, but beware that this may weaken the epoxy itself. Never do this until the epoxy is fully cured. (Give it 24 hours in summer or 48 hours in winter to be safe.)

Flaws with this design:
- Having to use epoxy is not ideal. Your seal assembly won't be centered perfectly because of this which may cause problems. Be careful when epoxying the seal assembly to the pump rod.
- Plastic parts would cost less and be less prone to rust than stainless steel or even aluminum. I will investigate making a plastic version of this pump when time and money permit, but you will likely need to order parts from McMaster for that.
- Rubber grommets (same dimensions) may be a better choice of seal than O-rings. I need to test that.
- Schedule 40 PVC's ID varies wildly (they only care about making the OD fit into the fittings). Clear PVC may be made to tighter tolerances but I cannot verify this. However, it is a lot more stylish, albeit expensive and I'm not sure how well it solvent welds with regular PVC. (If not, you will need a clear PVC male adapter.)

You can experiment with 1/2" PVC pipe nipples instead, which seem to have better tolerances to ID. Beware that their ID's are different though, and you may need to cut the pipe nipple to length if it's too long. Once cut, the cut end behaves as a typical slip connection for PVC. Pipe nipples are usually in Schedule 80. Don't get metal ones unless you don't mind the extra cost and weight, or unless your entire homemade is metal.

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Andrew
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Re: Pumps Guide - SuperPiston MK I and MK II

Postby Andrew » Mon Apr 15, 2013 6:05 pm

If you can find one long enough (and cheap enough :goofy: ), an internally threaded tube would work, and you could just thread on a pump handle at the other end!

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Apr 15, 2013 6:28 pm

That's a good find actually. The original idea I had was to tap using the screw, but the dimensions aren't right. Also, 9/16" (the diameter required of the screw in order to tap the aluminum rod) socket head screws do not fit in sch. 40 1/2". Socket heads are the best I can find for our application.

I will see if the threaded tube can be found on McMaster.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Wed May 22, 2013 11:35 am

Long story here, but I fixed the problems on the MK II. The solution was right in front of me, but I don't want to spend too much time getting into this, so I'll just give the bullet points:
- Take allen wrench, unthread the socket head screw.
- Remove nylon spacer, replace O-ring.
- I used two O-rings this time for good measure. One may be sufficient however, due to the additional friction caused.
- Re-apply silicone grease, place back on APH, rock n' roll.

I've learned a few things along the way.
- Sometimes, you just need a night's rest and you'll be thinking better the next day.
- (From chats with DX and forum discussions): Schedule 40 PVC ID varies enormously, possibly even amongst the same short tube of pipe. OD stays more consistent for obvious reasons. (Fittings.)
- Came up with solution to that: Use PVC nipples instead. However, I found that I did NOT need to do this, since the pump shaft I already cut sealed perfectly earlier from the outside of the O-ring. (It was the pump rod itself that didn't seal.)

All I really needed to do was get rid of that nylon spacer and get the O-ring(s) pressed tight with the screw.

Now, today I will need to head back to ACE to return probably $10 worth of parts, then buy a Schrader valve for Soakemore. *wink

What that means for this thread is that I'm going to scrap out the MK II for the time being. However, all that epoxying is here to stay, because it's been working so far, but the problem is that you'll still need a perfect cut on the end of the metal dowel for it to secure the O-ring(s) nicely.

On the other hand, the nylon spacer may not be a culprit at all. Perhaps all that was needed was to push the screw inwards to compress the O-ring seals, so that they seal against the rest of the seal assembly. One could argue that if I just used a nylon spacer with a groove cut in, I wouldn't have to worry about any of this. However, I don't have the tools for that. 3D printing revolution, feel free to join us anytime now.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby isoaker » Wed May 22, 2013 6:29 pm

I completely missed this post when it was created. This is a great write up; up for pushing it also to the wiki?

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Wed May 22, 2013 6:32 pm

I'll have to get to that after Soakemore, but I also have some APH documentation on the way. In the meantime, those who want a first look at the SuperPiston in action on my CPH and APH should definitely come to Soakemore this weekend. :goofy:

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby cohnhead » Sun Jun 09, 2013 9:49 pm

Hi. I am new to building. I just completed building the APH design http://www.sscentral.org/homemade/aph/.

The problem I am having is with the pump made out of a wooden dowel and an O ring. Either the O ring falls off, or the pump mechanism leaks. I found this coupling at Home Depot. Its is called an EZ span coupling. It seems to have everything needed to hold in pressure. I am just going to add an end cap so that it works properly. Does this look like a good idea, or am I doomed to fail?

Here is a picture of the coupling assembled:
8x6 whole.jpg
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And here it is taken apart:
8x6.jpg
8x6.jpg (51.79 KiB) Viewed 1181 times

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Jun 10, 2013 9:11 am

As long as the outer diameter (OD) of the O-rings fits in the pump shaft you chose, it should work. This does mean that you may need to have designed the pump to be adaptive to the rest of the blaster, a problem that SS's APH design does not adequately address with threaded parts.

A lot of the material on SSC is, unfortunately, outdated. It's still good reference, but lots of information needs to be rewritten. Unfortunately, there's little that can be done about it at the moment; I was working on an APH guide myself but ran into too many things to do.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby marauder » Mon Jun 10, 2013 10:17 am

Cohnhead, I would PM Drenchenator or Ben. I have never made a wooden pump, I've only ever used wooden dowels to reinforce plastic pumps by gluing them inside the plastic. I would also consider building an aluminum pump. PM GJIV if you want information on that.
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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Jun 10, 2013 1:33 pm

You could also wait until I finish revising and updating this guide. For now, best solution is the MK II without the nylon spacer but I will detail that a bit more later.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby cohnhead » Mon Jun 10, 2013 4:36 pm

Where can I find a guide for building the MK II or the MK I?

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby the oncoming storm » Mon Jun 10, 2013 5:35 pm

I have had good success with homemade pumps, Just take a dowel cut a small grove for your O ring and use Electrical tape on both sides of it to hold in place... Oh and don't forget to lube it.


How much did you spend on the APH you put together ?
If you ever bother reading these, I worry for your mental sanity. :oo:

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Jun 10, 2013 6:32 pm

Electrical tape will last you a few pumps before it starts getting displaced. Dowels have to be plastic or non-rusting metal (the wood leaks slowly and rots quickly because, well, you know, WATER?!?!?) and grooves have to be cut absolutely perfectly (need special tools for that; a good lathe perhaps?) or the O-ring won't seal at all. (Or will seal for a few pumps before leaking.) I still don't have the slightest clue how Ben got any of that stuff to ever work. (As in, lasts for months or years.) Meanwhile, my MK I pump for the CPH is still rockin' out. I brought it to Soakemore and it worked just fine. They're not as great as stock blasters' skirt seals, but they do work and last, and that's what I need.

It goes without saying that I build strictly for water warfare. I want things that are useful for it (or at least help lead to something useful for it), but a lot of homemade designs out there just aren't cut for the job.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby the oncoming storm » Mon Jun 10, 2013 7:32 pm

Well it may only last a year or two but it only costs $1 and about 5 Minutes to make basically unless you plan to your homemade for 10-12 years wooden pumps make more sense.
If you ever bother reading these, I worry for your mental sanity. :oo:

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Mon Jun 10, 2013 7:52 pm

Yeah, it lasts a year if you use it once or twice, and you still need a lathe to make it properly. (Although I could most certainly adapt a version of the SuperPiston that also uses a lathe, but it'd be about the same design as the one Wetmonkey made earlier.) Stainless steel and aluminum are pricey, but it's the cost of making the thing actually work. (And unfortunately they don't seem to sell plastic-based dowels at the correct OD's we need.)

All seals will eventually rot out anyway, particularly O-rings in general. I'd give mine a few years before having to replace it. Even pump seals from CPS's are failing now since they've been around for a long time.

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby DX » Tue Jun 11, 2013 12:00 am

2000/2500 pump seals are failing because they are thin and suck. The 1000 style seals are virtually indestructible and seal perfectly even without lube. I'm still going to hold out for future designs. For now, I am cutting up the pumps from broken guns and future-proofing the pump shafts with threads, so the pump can be changed out if a 100% perfect homemade design pops up.
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Re: Pumps Guide - SuperPiston MK I and MK II

Postby HBWW » Tue Jun 11, 2013 12:43 am

Let's define "100% perfect", just to get things started:
- No leaks under any circumstances (no duh).
- Easily reproducible, anyone can build with widely available parts/suppliers/tools.
- Durable, must stand up to regular combat use long term.
- Should not require any lubrication, yet operate smoothly.
- Should be within reasonable cost.
- Should be adaptable: easy to build to different lengths and even give choice of diameters for high volume pumps.

Essentially, we want the precision design and perfection of the right stock pump seal with the durability and design flexibility of a proper homemade pump.

So far, the SuperPiston lacks in low cost (those aluminum dowels cost about $10 these days) and requires lubrication to get started. The O-rings must be worn out to the ID of the pipe, whatever it happens to be. After that, things operate much more smoothly. (However, since no one really checked out my homemades in detail in Soakemore, you guys wouldn't know lol.) The main challenge to the SuperPiston design is if you get a really odd ID of the pipe, in which case you ought to be measuring it anyways to ensure it's within 5/8" of the O-ring's OD. There's a small possibility that you may need 9/16" OD if the pipe is very tight, but I've gotten 5/8" OD to work with two different pipe ID's so far. (Although the variation between them isn't as crazy as what DX has experienced.)

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby Drenchenator » Tue Jun 11, 2013 8:08 am

Image

I've posted about my design before. To me, it's a 100% functional pump design without any glaring flaws. I think it addresses most of those points.

I'll address the points in order:
- With two grommets, the design doesn't leak. One grommet will leak slightly, but two grommets seal extremely well.
- It doesn't require any fancy fabrication techniques or materials. It's just a dowel (wood or plastic can work), a #8 screw and washer, and two 5/8 inch OD rubber grommets. Screw them all together and it's a pump rod for 1/2 inch PVC pumps. In all, that's about 5 minutes of work, and unlike my previous design, no sanding or stretching is required.
- I've used the same design since I build Riptide in 2009, so it's fairly durable.
- The pump does require lubrication since the seals are slightly larger than the pipe's ID. I think requiring lubrication is a good thing, since removing it would just wear parts down more and make the pump harder to use.
- The cost is about as low as possible.
- The design could be abstracted a bit more, and can be adapted to other diameter pumps. I haven't found a good set of rubber washers for 3/4 inch PVC yet, but I'm sure they are out there.


The problem I am having is with the pump made out of a wooden dowel and an O ring. Either the O ring falls off, or the pump mechanism leaks. I found this coupling at Home Depot. Its is called an EZ span coupling. It seems to have everything needed to hold in pressure. I am just going to add an end cap so that it works properly. Does this look like a good idea, or am I doomed to fail?

This will work, but it won't work well. If I remember correctly, they don't move much water in a single stroke. But what's worse is that the inner diameter is very high, so you wouldn't be able to build up a lot of pressure before it becomes difficult to pump. I would not suggest using it for those two reasons.
The Drenchenator, also known as Lt. Col. Drench

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby cohnhead » Tue Jun 11, 2013 8:42 am

the oncoming storm wrote:I have had good success with homemade pumps, Just take a dowel cut a small grove for your O ring and use Electrical tape on both sides of it to hold in place... Oh and don't forget to lube it.


How much did you spend on the APH you put together ?


All together, it probably cost me around $100

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Re: Pumps Guide - SuperPiston MK I and MK II

Postby cohnhead » Tue Jun 11, 2013 8:50 am

Drenchenator wrote:
This will work, but it won't work well. If I remember correctly, they don't move much water in a single stroke. But what's worse is that the inner diameter is very high, so you wouldn't be able to build up a lot of pressure before it becomes difficult to pump. I would not suggest using it for those two reasons.


That is exactly what happened. I tried it before I saw your post, and it is really hard to pump. Does your grommet design build up a lot of pressure? I will have to cut it off and try it with a dowel.


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