My first CPS

Build a homemade water gun or water balloon launcher and tell us about it.
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Titan
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Joined: Mon Jun 28, 2010 2:08 pm

My first CPS

Post by Titan » Wed Jul 07, 2010 6:57 pm

hey guys, n00b here, I've done a lot of reading on the site and I'm almost complete with my first soaker

regarding the hose barb size for CPS bladder, does this really need to be larger than the tubing ID?

I have 2 layers of 3/16" wall LRT 3/8" diameter and plan to use a 3/8" hose barb

My nozzle is a 3/16" hose barb, being 1/2 the size of my bladder hose barb the only issue I can see is that it will take a fuzz longer to fill anything before the nozzle after the firing valve, but we're talking miliseconds here aren't we?

Thanks for the help, I'll post pictures tonight, according to UPS my tubing is on the porch :D

I used cheap hardware store LRT just to try it out, I got too anxious while waiting for my order with the holiday weekend, 2 layers of 1/16" wall thickness obviously did not hold up but it did fire about as far as my XPS150 with a much more layered stream

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Killi101
Posts: 89
Joined: Sun May 30, 2010 11:30 pm

Re: My first CPS

Post by Killi101 » Wed Jul 07, 2010 7:38 pm

well i dont make cps' or know much about them but i think it should be bigger as the rubber should have a tight seal on the barb, and the rubber would be able to strech on the barb because its strechy!
Water:
dont like drinking much
like to throw it at people

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C-A_99
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Joined: Tue Aug 01, 2006 11:09 pm

Re: My first CPS

Post by C-A_99 » Wed Jul 07, 2010 7:47 pm

The purpose of having a larger hose barb is for better flow, while a smaller tubing ID is so that the tube can squeeze out more water. You'll want a hose barb at least 3/8";1/2" will provide good flow. However, with a tubing ID at 3/8", you'll need to stretch the tube over the barb. There should be some tricks on how to do that listed around the site but it's not as easy as just slipping the tube on, which is only possible if both the tube's ID and the barb's diameter are the same. If you prefer to do it that way, you'll have to sacrifice flow (by using 3/8") or quantity of water that can be squeezed out (1/2").

As for the area between the nozzle and ball valve, usually that spot is partially filled, but you want to minimize the volume there if possible to avoid excess "leaking". Unless you have some 10ft long barrel, just a few inches of extra nozzle space won't affect the time from the valve's opening to the stream coming out significant enough to be noticed. Stream velocity is the real issue as it affects how long the stream takes to reach a target, thus determining how easily it can be dodged. Hose barbs make somewhat decent nozzles; they perform fairly well but conical nozzles (such as well-manufactured water balloon fillers) can do a better job.

If you need more power, it's possible to buy more tubes to stack over the initial ones; buying extra tubes whose ID's are barely larger than the base tube's OD may not be a bad idea, but I'm not entirely sure on this. Supposedly, if an extra tube's ID matches the base tube's OD, it gets difficult to put on but that's my guess. Either way, you'll want to cut the new tube to the same length as the old one, slip it over, and use larger hose clamps to clamp down the new tube. It's a good idea to wrap electrical or duct tape around the area you're clamping so that the clamps do not cut into the tube. (However, this is a one-time solution.)

You may also be able to use crafting balloons to layer over the base LRT tube, which would be cheaper but has not been tried before.

Keep in mind that LRT is not the only option for CPH's. Stacks of party balloons have also been tried in the past, but it's a bit trickier to make a case/container for them. You need a case for the bladder to prevent it from wiggling around annoyingly and causing problems with ergonomics. A case also protects the bladder.

Good luck with the project.

Titan
Posts: 11
Joined: Mon Jun 28, 2010 2:08 pm

Re: My first CPS

Post by Titan » Wed Jul 07, 2010 7:57 pm

I'll give it a shot with the 3/8" hose barb, if it's too wussy, I'll go buy a new hose barb, I bought 2' of LRT, I'm planning to only use like 10" of it and keep the rest for spare or the next soaker

I built a APH first and wasn't happy with the design (It was super hard to pump) so this one has threaded fittings everywhere so I can re-use parts if I change the layout/design at all

after layering 2 pieces of the cheap 3/8" tubing of the same size the LRT I bought should be much simpler 3/8" ID, 3/4" OD and 3/4" ID, 1-1/8" OD

I plan to use corn starch as the lubricant to "layer" them

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C-A_99
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Joined: Tue Aug 01, 2006 11:09 pm

Re: My first CPS

Post by C-A_99 » Thu Jul 08, 2010 1:42 am

Buying extra LRT is pretty typical since the tubes do burst eventually if overpumped.

I never built a standard APH actually. I'd think that if the pump seals properly and if the PC's aren't too big, it shouldn't be that difficult to operate.

Titan
Posts: 11
Joined: Mon Jun 28, 2010 2:08 pm

Re: My first CPS

Post by Titan » Thu Jul 08, 2010 12:35 pm

C-A_99 wrote:Buying extra LRT is pretty typical since the tubes do burst eventually if overpumped.

I never built a standard APH actually. I'd think that if the pump seals properly and if the PC's aren't too big, it shouldn't be that difficult to operate.
I went 1" on the barrel and check valves, so I'm sure it was too big ;)

I can post a pic of this one as well as a "Don't build this!" example, it did fire a fair distance but I didn't think I was getting enough out of the amount of work I was putting into pumping it



anyways, the 3/8 tubing barb doesn't grab the 3/8" ID tubing at all, I'll have to pick up a larger one

using corn starch to "lubricate" the tubing worked fantastic, I pushed a 1/2" dowel about 1" into the smaller tubing, made a mess of the corn starch on it and then put a fair amount into the larger tubes as well and it pulled right thru on the first shot

the stream is not very well laminated with the hose barb nozzle but that could be due to the smaller hose barb connecting the bladder, I'll test with the new one before posting pics

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Silence
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Re: My first CPS

Post by Silence » Tue Jul 13, 2010 8:01 am

[quote="C-A_99"]a smaller tubing ID is so that the tube can squeeze out more water.[/url]
Not exactly. It's obvious that more thickness means more pressure; but the maximum outer diameter of tubing that McMaster-Carr sells is 1.5 inches. Thus you need to decrease the inner diameter in order to increase the rubber's thickness. Obviously, this will then start to restrict the flow...

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