simple homemade cps gun help

[Commander Soakage]

ok, the price for the aph was listed at about $58, killer7 told me the price for the cph was about $150. gee I wonder which price I'd rather pay (rolls eyes)

[Drenchenator]

A CPH can be very cheap. Just because Killer7's one cost so much doesn't mean that yours needs to. If you just keep it simple and don't do anything excessive, I can see a 40 USD CPH. The most expensive part is the LRT; the rest can be picked up at Home Depot or Lowes for under 20 USD. And from what you said, getting LRT was no trouble. Is 40 bucks too expensive for you?

[Ben]

That was for his CPH, not the one I built or the one you could build. And he said that a large part of the cost was spent on rubber tubing that he didn't use. Read his post here.

Also, you're comparing prices in December 2004 to prices today. Inflation and gas prices makes the 2004 prices cheaper. I'd imagine an APH today could cost 25% more.

Regardless, I'm still confused as to how your design is significantly different from my own. Again, I'd like to point out that the ONLY difference between your design and SuperCPS is the position and orientation of a few pieces. That means that it will cost the same as SuperCPS.

[Commander Soakage]

I think I just thought of another idea. i think i'll put the check valve in the handle to avoid needing 2 elbows and an extra pvc pipe
kind of like thiscph1.jpg

[Ben]

That would be fine. You'd need to move the pump up so that the end of it is where the check valve is, but other than that it would work.

Be warned that check valves don't make the most comfortable handles.

[Commander Soakage]

to solve the handle problem i'll simply put a piece of thin pipe insulation

could I use PETG for the pc casing?

[Drenchenator]

Yes, it's only a structural element, so you can pretty much use whatever cylindrical object you want. Ben used some clear PETG tubing in his Arctic Blast PC expansion. It worked well.

[Ben]

Sure you can use PETG for the PC casing. There's nothing stopping you. It should work great and look great. The only problem would be that PETG doesn't come in sizes larger than 3.5 inches in diameter (at least on McMaster-Carr), but local places might have a better selection.

[Commander Soakage]

this may sound silly, but would an old coke bottle work

[Ben]

Sure. As Drenchenator said, any cylindrical object would work. With a soda bottle you have the advantage of having an end built in. You also are recycling a bottle, which saves money and helps the environment. However, it might be too flexible, but that might not matter to you.

[Commander Soakage]

so a modified cost value. if I replace the pc casing w/ a 2 liter coke bottle and take simplify the section i mentioned in post #34. how much would it cost considering i already have the LRT.

a couple more questions though: how much does it cost to make a backpack resivor and would it be effective to use a coke bottle for a resivor

[Drenchenator]

I'd say you could likely get the rest of the parts for 20 to 30 USD. The valves would be the most expensive parts, at probably about 5 USD each. The dowel for the pump would probably be 3 USD, which odds and ends maybe 10 with pipe--assuming you are using 1/2" PVC of course. But this all depends on what's available in your area though. Prices can vary and there's nothing anyone can do about it.

A 2L bottle could work as a reservoir, but it wouldn't provide a lot of water. I'd recommend using several and making a simple backpack arrangement from there. Don't forget the vinyl tubing to connect the gun and backpack though.

[Commander Soakage]

20 to 30 dollars is F***ing cheap for the performance it gets. I'm going with that. i think I solved the problem of pvc by buying scrap and leftover pvc. which would probably be even cheaper since i'm buying it used.

[Drenchenator]

I gonna have to be forward and give you a tip. If you really want performance, don't worry about the cost. I'm not saying that you can't built something that's cheap and good; I'm just saying that it's not going to be easy.

There's an old adage in engineering. Good, fast, cheap--pick two. It means that when you have a project, you probably don't want go make everything good, fast, and cheap because it would be a true hassle. You seem to be going for fast and cheap. Don't expect for the final product to be that "good." It could have decent performance, but don't built it thinking "This should shoot 60 feet no sweat!" You get out of a project what you put into it.

[Commander Soakage]

i'm going for good and cheap and it doesn't matter to the performance if the pvc is leftovers as most of the piping are short pipes. I just need a little more clarification on the topic of the pc. ben says that 1/8 inch will only hold 25 psi. I'm going for about 40-50 psi. what can I do (short of ordering from mcmaster carr) that would help. ben said to use a bike inner tube, but I don't have one that fits tightly over it. the tube has an outer diameter of about 1/2 inch. I was wondering if you could cut the inner tube lengthwise like so:
tube.jpg
and tape or glue the cut line back together after making it overlap to make it 1/2 inch inner diameter.