My new CPS system (Almost Done!!!)

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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Fishfan
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My new CPS system (Almost Done!!!)

Post by Fishfan » Mon Jun 11, 2012 1:36 pm

I have just built myself a new CPS water blaster, except for the LRT (that comes today). Yesterday I just got the right sized o-ring (sealed fairly well at first) and I made a few modifications to make it easier to pump(cutting a bigger groove, widening the pump cap) but now it seals poorly. I read on another post that maybe I should try to use several o-rings. I think I will try that, but if anyone has any sugestions I would really apreciate it.
P.S. The reason I chose to build a CPS system first instead of an APH was because 3-inch and 4-inch schedule 40 pvc pipe is not available where I live. I also liked how there was no pressure drop off over shot time in the water gun.
Last edited by Fishfan on Fri Sep 28, 2012 5:52 pm, edited 1 time in total.
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Andrew
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Re: My new CPS system

Post by Andrew » Mon Jun 11, 2012 2:32 pm

Welcome to WWn!

A CPH is a pretty good place to start if either an APH is harder to source parts for, and you have a fair idea of what you're doing. Have you been following the SuperCPS guide on SSCentral, the CPH guide on the WWn wiki, or just by adapting the APH design?
Fishfan wrote: I made a few modifications to make it easier to pump (cutting a bigger groove, widening the pump cap) but now it seals poorly.
When you say cut the larger groove do you mean you cut the groove deeper? The o-ring should be pretty tight to get the best seal. That is, the best seal should actually make the pump feel harder to pump, as you make it easier to pump by lubricating the o-ring and the inside of the pump housing. As you are using LRT you must avoid using Vaseline or any other petroleum-based lubricant, as it will degrade the natural latex rubber. If you cut the groove deeper, it will be easier to pump but it won’t seal properly.

When I made the first pump for my low pressure drop-off/pre-charger/super-charger homemade (still not sure what to call it :goofy: ), I used two o-rings in a wooden dowel but cut the grooves slightly too deep. If you don’t fancy starting the pump rod groove again, you can decrease the depth of the current groove by lining a few turns of Teflon thread seal tape between the o-ring and the dowel. You can then secure the edges of thread tape to the pump rod dowel with electrical (PVC) tape either side of the o-ring. If you don’t secure the tape, it will be pulled out of the groove when pumping.

That first pump had two o-rings and, to be honest, it only really improves the seal if the dowel doesn’t fit snugly inside the pump housing. In my pump one of the o-rings sealed slightly less well than the other, so if one leaked, both leaked. Using two o-rings also means more friction making it harder to pump.

The newer brass pump rod (the wooden rod snapped) fits very snugly and uses one very tight fitting o-ring (so much so it takes a fair bit of force to push it into the pump housing when assembling). I lubricated it, and it pumps pretty smoothly and holds quite a bit of pressure without leaking.

Could you post pics of what you've done so far?

Fishfan
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Re: My new CPS system

Post by Fishfan » Mon Jun 11, 2012 6:59 pm

http://imageshack.us/photo/my-images/39/sdc11201.jpg/
http://imageshack.us/photo/my-images/546/sdc11202q.jpg/
http://imageshack.us/photo/my-images/252/sdc11207.jpg/
http://imageshack.us/photo/my-images/14 ... 208tr.jpg/

I am using the SuperCPS guide on SScentral
The reason I cut it deeper is because the male screw adapter is slightly smaller than a 1/2 inch pipe, making it extremly hard to put the pump in. I can't imagine trying to have it tighter. Also, My experience with electrical tape is that whenever it is wet, it slides right off.
My dad said I didn't need to lubricate it, water would just wash the lubricant away. But if your saying it works, I might use it. Should I use silicon lubricant?
P.S. Why is everyone saying that LRT is hard to layer? It was a piece of cake for me!
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Jeffman3
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Re: My new CPS system

Post by Jeffman3 » Tue Jun 12, 2012 1:20 am

KY His + Hers is a very high quality silicone-based lubricant. Don't ask me how I know this. Water will not just wash it away. Don't ask me how I know that, either.

My pump is thin-wall 3/4" tubing with a 1/2" PVC pump shaft... I run a three-layer seal just because I'm all into over-engineering things. Works well. I use automotive grade o-rings so I can get away with using Vaseline. :lol:

Andrew
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Re: My new CPS system

Post by Andrew » Tue Jun 12, 2012 7:19 am

Fishfan wrote:The reason I cut it deeper is because the male screw adapter is slightly smaller than a 1/2 inch pipe, making it extremely hard to put the pump in.
You might have to expand the adapter so it is slightly larger than the pump housing ID. That fitting won't be holding any pressure so that shouldn't be a problem. It was hard for me to get the pump rod into the pump housing without a fitting on the end of it. I haven't fitted an end-cap, I just made the pump slightly longer than I can physically reach when it's in my shoulder, and added some strips of black electrical tape to the pump rod, to tell me when to stop pulling the pump rod further (for when it's not in my shoulder).
Fishfan wrote:My experience with electrical tape is that whenever it is wet, it slides right off.
As long as the surface it sticks to is dry and free from lubricant, and it is wrapped tightly there shouldn't be a problem. The electrical tape just stops the Teflon tape from moving beneath the o-ring. As mentioned, I've used the tape on a wooden and brass pump rod with no problems. Like Jeffman3 I managed to use Vaseline for lubrication as the rubber components in my homemade are petroleum resistant. Silicon lubricant works well on stock CPS blasters so it should work well on a PVC homemade as well.
Fishfan wrote:P.S. Why is everyone saying that LRT is hard to layer? It was a piece of cake for me!
Either there is a slight gap between the OD of the inner layer and the ID of the outer layer, or your method of layering is pretty good.

You probably know this, but you'll have to put some kind of retainer ring on the other side of the o-ring in your images, otherwise it might pull off if you pump too quickly.
Jeffman3 wrote:KY His + Hers is a very high quality silicone-based lubricant. Don't ask me how I know this. Water will not just wash it away. Don't ask me how I know that, either.
:lol:

Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 9:37 am

I cut a new groove farther down the rod. I can't upload any images right now because image shack is acting weirdly. Anyways, I tested it on a separate piece of pipe and it is so hard to pump that the o-ring actually rolls out of the groove a little bit. I put soap on it to lubricate it and it went through it a lot easier. Now I just have to widen the adapter. Maybe could I do that with a 1/2 inch paddle bit? I don't have anything that big but my neighbor has a 1/2 inch paddle bit. Maybe I just should use a pocket knife. I looked online for KY silicone lubricant and $15 for a 2.75 oz container! That is outrageous! Is there any silicone lubricant that is cheaper than that?
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wetmonkey442
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Re: My new CPS system

Post by wetmonkey442 » Tue Jun 12, 2012 9:43 am

Nice CPH Fishfan! I'm glad to hear that you are focusing on your pump design, because that is the source of problems and headaches for most homemades.

Please keep us updated with pictures as the build comes together!
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Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 10:31 am

I tried to widen the hole more with a pocket knife, pump still won't go in. Sometimes when I tried to get it in the o-ring slipped out of the groove. I even lubricated the adapter with dish washing soap. Ugh, this is frustrating.
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Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 12:11 pm

I got the pump in, and now I'm having a whole slew more problems. I tried pumping it some, and it still leaks. I managed to get some into the LRT, and it is leaking at the bolted end. I am using a 3/8 inch bold with 3/8 inch LRT ID. Is that sufficient? Should I use a 1/2 inch bolt? Or should I tighten the clamp more? And how should I solve the problem with the pump?
I managed to get a small 10 foot riot blast with it. I didn't see a bump in the LRT when I fired it, and that makes me even more determined to finish this baby up.

P.S. Next time I am going to make a pump with an aluminum rod. This wood doesn't work so well.
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Andrew
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Re: My new CPS system

Post by Andrew » Tue Jun 12, 2012 12:30 pm

Fishfan wrote:I tested it on a separate piece of pipe and it is so hard to pump that the o-ring actually rolls out of the groove a little bit.
Sounds like the pump rod's a little narrow. To be fair if it was wider you couldn't use a drilled end-cap to stop the pump coming out the end of the pump housing. A few layers of electrical tape either side of the o-ring (enough so that the pump rod diameter is very slightly smaller than the internal diameter of the pipe) should help to stop the o-ring slipping out of the groove when putting the pump rod into the blaster. It also means the o-ring won't slip out of the groove when the pump is fully assembled.
Fishfan wrote:I tried to widen the hole more with a pocket knife, pump still won't go in.
How wide is the adapter hole now? As long as it's wider than the ID of the pipe it should be enough.
Fishfan wrote:Maybe could I do that with a 1/2 inch paddle bit?
It would work, but you'd ideally need a bench drill press to cut it accurately with enough control (i.e. very slowly).

EDIT:

Ninja'd! :goofy:

Yes I'd go with the larger bolt, and tighten it a bit more as-well.

If the pump is still leaking, then either the seal still isn't tight enough or water is leaking past severe imperfections in the grooves or o-ring itself. A thin layer of Teflon tape between the o-ring and dowel can actually help the o-ring seal as-well as making the seal tighter. It reduces the effect of some imperfections in the groove.

I must admit, the brass pump rod (had to use brass, aluminium would corrode in contact with the copper pipe) is sturdier (the wooden rod snapped in the end) and if cut well seal better. The only problem is you need a lathe to properly cut a groove into aluminium or brass. A file won't cut it as accurately, but is useful for finishing the groove. I managed to improvise a lathe with a clamped drill, the pointy end of a paddle drill bit (the bit was vertical to give a square-ish bottomed groove which was rounded with a file) and a block of wood clamped to a workbench (to support the end of the pump rod). It didn't do the drill much good (hence only one groove was cut).

Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 1:11 pm

I can't seem to get the larger bolt in there. I tried melting an ice cube on the bolt but I didn't get it on there. The 3 layers doesn't help either. Maybe I should take the duct tape off the LRT and and roll the outer layers back. Oh and by the way, on My LRT The smallest layer has the same outer diameter as the inner diameter as the 2nd layer, and same with the 2nd and 3rd layer.
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Andrew
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Re: My new CPS system

Post by Andrew » Tue Jun 12, 2012 1:22 pm

Three layers of LRT is fairly thick (which won't help sealing the bolt). You'll need that pump to seal very well to pressurise that. If you can't fit the bolt in, then rolling back the layers is a better option than trying to force it into the LRT.

Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 1:25 pm

I'm thinking maybe I should cut off the screw-on adapter alltogether. My dad sugested I put it there so I could replace the o-ring when it wore out, but I am just thinking when that happens just cut the endcap off. Should I do that? Because this is getting so frustrating.
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Andrew
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Re: My new CPS system

Post by Andrew » Tue Jun 12, 2012 1:30 pm

You don't really need an end-cap at all, it's just a nice addition that makes the blaster more user friendly (by stopping you from pulling the pump rod out of the blaster). If you really want an end-cap I would strongly suggest you persevere with the adapter. When you cut the end-cap off you'll shorten the pump housing slightly. The o-ring won't wear out for a long time, but it is possible for your pump rod to snap, or something else might happen, and you may need to disassemble it to fix the problem.

Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 2:40 pm

Okay, I guess I'll keep the screw on adapter. I have put the bolt in the LRT. Now I have to get the clamps on and pray to the water gun gods that it seals properly. :lol:
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Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 2:58 pm

Great. I am one happy camper. The entire pump housing came off when I was trying to pull the pump out.
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atvan
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Re: My new CPS system

Post by atvan » Tue Jun 12, 2012 3:06 pm

Did you not solvent weld the PVC together?

As a general note, don't double post unless you are adding something useful and relevant to an old thread (not reviving old threads from inactive members mind you), but instead edit your posts.
DX wrote:In the neanderthal days of K-modding, people would lop off the whole PRV
Well, not that much soakage.
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Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 3:44 pm

Ok. I will be more aware of that in the future.
I used PVC cement. I actually was expecting it to come off because I didn't get the pump housing all the way into the tee when I was cementing it. Anyways, I'm still stuck with the pum stuck in the pump housing. Maybe I'll play tug-of-war with my dad when he gets home. I can't wait to get this thing working so I can do this: :cps2000:
Edit: it also seems like my o-rings are disapearing. Whenever I pull it out of the housing, they aren't there anymore. They aren't in the pump housing. Oh and also I got the pump out of the housing
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atvan
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Re: My new CPS system

Post by atvan » Tue Jun 12, 2012 4:16 pm

Look inside the gun.

You must have done something wrong when you solvent welded- it is supposed to dissolve th plastic and then evaporate, forming a single piece. Are you not woried that what is essentially a pressure vessel is falling apart?
DX wrote:In the neanderthal days of K-modding, people would lop off the whole PRV
Well, not that much soakage.
Beware the Purple

Fishfan
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Re: My new CPS system

Post by Fishfan » Tue Jun 12, 2012 4:28 pm

I didn't push the pvc pipe all the way into the tee when I cemented it.thats the reason why it came out. I don't understand what you mean by solvent welding. Are you talking about using PVC cement to put it together? Anyways, that's the only thing that was creaking when I was working with the pump and LRT.

I'm thinking of getting an aluminum rod from home depot. The only thing is it that it is $8 and my parents will not be happy about me spending more on this water gun.
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