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Homade Cps?


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#1 texmustache

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Posted 22 July 2004 - 02:15 PM

Okay i had an idea for a home made constant pressure system, which would be good for semi-autos so you don't lose power.

Materials

For the CPS System

Rubber tubing with high durability and pressure
Hose clamps
1" PVC coupler
1" PVC
1" Endcap
1.5" PVC
1.5"-1" Reducer
PVC Glue
Tire valve

What you do first is you take one coupler and cut a 4-5" piece of PVC. Glue them together. Drill a hole in the endcap for the tire valve and stick it in. Then take another 4-5" piece of PVC and glue that to the endcap. Next, put the bick tubing over either piece of PVC. Take multiple hose clamps and clamp it real good. Then take the 1.5"-1" reducer and look inside. You should see a lip that keeps the 1" PVC from going to far back. Sand that down read good. Then, glue so 1.5" PVC to the big end. make it a foot or so longer that your bike tube/coupler assembly. Then, glue some 1" PVC to the 1" coupler on the open end, and slide the 1.5" reducer+1.5" PVC over it.

Now you have your CPS system.

To make it semi auto, take to valves(ball or solenoid, solenoid would really speed things up.) attach one to the 1" pvc, add a little pvc, then add the next one. finally, add your barrel on.

to fire you hit the back one, then let it go and hit the front one.

What i want to know is...
Is this reasonable to make.
Is it SAFE?:
would the clamps keep the tube on
would the tube provide much pressure?
http://www.freewebs..../cps system.jpg
i wish the image worked...ill try and get it up.

Edited by texmustache, 23 July 2004 - 10:46 AM.

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#2 Jangadance

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Posted 22 July 2004 - 05:35 PM

Is this reasonable to make.
Is it SAFE?:
would the clamps keep the tube on
would the tube provide much pressure?

My speculation is YES to all. You'll have to try it for yourself though.

The PSI of the bike tire is listed on the unit, check for specifications. I personally don't think a bike tire will have very much resistance alone, it's far too thin. Maybe multiples or a thick tire tube. Good luck.

edit: also, www.sscentral.net, Doom's website has some great CPS homemade technology items. Check that out.

Edited by Jangadance, 22 July 2004 - 05:37 PM.

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#3 Doom

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Posted 23 July 2004 - 09:10 AM

Bike tube: high durability and pressure


Please, don't even joke about that. A single bike tube will never get too much pressure. I only will reccomend what I call CPS tubing, latex rubber tubing from McMaster. That stuff is much better, I admit is more expensive and you have to wait for it to arrive, but you can practically specify the thickness.

If you want to see a "Homade CPS", look no further than this: http://forums.sscent...?showtopic=1261. 63 foot range isn't too bad for a water gun (effective range is 58 feet). Saying that a modded CPS 2500 which shoots water maybe 45 feet at most gets over 200 feet in range, one can only imagine how well that gun would perform shooting a Nerf dart.

I have made a Nerf homemade with a tube that is 3/16" thick just to test it (Note: it wasn't cemented together because the tubes are so low pressure). That performs similarly to my recent air pressure Nerf homemade. Actually a little bit worse, but that may have been due to leaking because I didn't cement it.

I actually have been working on a semi-auto system using a CPS tube I have. I'm making it out of leftover parts and now I don't think I'll be able to finish it. If you have the money, I will recommend making an air backpack and using a regulator to save you a lot of time. The CPS tubing stuff is constant pressure, but it's too much of a hassle to work with. I've seen it all happen to the homemade stuff, bursting off the barbs even with tubing clamps on tight, popping, the fact that it gets thinner with use, it's only for water guns. Maybe as a cost effective solution you could use it, but a regulator with an air backpack set-up should hold more air and be more powerful.
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#4 Techno-Dann

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Posted 23 July 2004 - 02:13 PM

Well... I've done a little bit with bycicle inner-tubing. The inner tube I had fit fairly well over 3/4 in. PVC pipe, but was a little loose. It's possible to get a good seal with a few hose clamps: Squirt lots of hot glue around between the inner tube and the pipe, and then put the hose clamp directly on top of the hot glue, and make it really, really tight. That's how I held the valve stem onto my homemade.

I don't think that inner tube would make a good pressure tank, though. It strikes me as being much to soft and elastic. *points at Doom's post* Try that instead.
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#5 Doom

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Posted 23 July 2004 - 03:40 PM

Ok, since everyone seems to be really clueless when it comes to CPS tubing I'll explain what I know that applies to Nerf.

First, you never, ever attach any tube to straight PVC, or even a male threaded adaptor. Doing so is like asking to have your gun fall apart in your hands. You should only use barbed fittings, they have an end for tubing and another threaded male end that will screw into your female threads. You also are required to use tubing clamps, because if you don't then after one or two pumps your chamber will pop off. If they aren't on tight enough, especially in a water gun, the stuff could pop off at a very high velocity, and you don't want to get hit by that.

The CPS tubing should be smaller than the barb you are using. That will let you stretch the smaller one over the larger tube. In my gun I didn't do that, but that was because I made it out of leftover parts.

The site for all your CPS tubing needs is http://www.mcmaster.com. Go there and search for latex rubber tubing, what it is actually called. The thing will list all the info you should need to know. I think the PSI actually is the amount of pressure it takes for the rubber to expand. Just get the thickest you can get, and then get something to put over that, something where the ID is slightly larger (not the same) and the OD of the smaller tube. That will let you make it thicker, and not spend hours trying to get something with and ID the same as the OD on. Don't make that mistake.

The Elongation of the tubing is 850%, which means that if you multiply the ID by 8.5 and then add the thickness of the tubing times 2 you'll get about the size of the tubing when expanded. For multiple tubes, just add up the thicknesses. Don't make any jokes about how you can order this stuff in black and how it gets 8.5 times longer either, that is just silly comparing this stuff to that.

http://www.sscentral...to/DSCN0102.JPG

There is my gun so far, if you want more info about it I'll make a new topic (it is far from finished). You can see the CPS tubing at the bottom, both ends sealed, one with a barbed fitting and one with a big screw because I ran out of barbed fittings and threaded endcaps. ou can't see it, but the clamps literally are cutting into the tubing, when it gets to that point you should stop. I've considered covering the ends with electrical tape and then putting the clamps on so that it's cutting into the tape instead. You should house this thing is some PVC about the same ID as the OD of the tubing. This stuff gets about 3 inches and 1 sixteenth big, which is close enough to 3 inches that I'd use some of the 3 inch PVC I have so much of. If it's like 3 1/2 inches then you should use 4 inch because it's not close and it's better to have more air.

If you've got any more questions about CPS systems just ask, I probably know it.
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