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Some help before.....

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Some help before.....

Unread postAuthor: Mr. Beaver » Mon Dec 10, 2007 6:08 pm

so i'ts like this i'm going to buy the stuff for my first pneumatic cannon in a day or two and it's down to this :
i already got the plans of what i want to build and a list of what i need, i'm just afraid cause it's my first cannon, and i don't wanna mess everything up, cause of the costs and/or whatever so i want to be sure of everything, so i'll just ask everything i want to know.
again i got the plans for it so here it is (more or less) :

Image

so plz i need some :help:
1. what should be the barrel's and chamber's length (i want to make it portable and the chamber chubby).
2. how i connect the barrel to the chamber as in the draw.
3. how do i connect the shcrader valveand pressure gauge to the chamber without tapping.
4. how do i connect the support thingy to the chamber without the air coming into it (glueing it from the outside wouldnot be enough), also could i attach it to the barrel using a T?
5. and last, is the schrader valve size for a hand pumd is the same with the compressor, if it is what are the size for each..

ty for all your help, if your survived reading the all damn thing feel free to reply but plz no flaming i can say myself i'm stupid i don't need you to mention it :)
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Unread postAuthor: PVC Arsenal 17 » Mon Dec 10, 2007 6:15 pm

1. I don't know much about C:B... 1:1 maybe?
2. Glue? Threads?
3. PVC is soft enough that you don't really need to tap (though I usually do) If you have 1/8" threads use a 5/16" bit.
4. I'm not sure what you're asking.
5. They are the same. To fill with a compressor you'll need a tire chuck.
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Unread postAuthor: Mr. Beaver » Mon Dec 10, 2007 6:24 pm

ty but what is the 5/16" bit and also what do u mean with me needing a : 'tire chunk'=??
:oops:
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Unread postAuthor: PVC Arsenal 17 » Mon Dec 10, 2007 6:27 pm

Perhaps this isn't such a good hobby for you... nah I'm only kidding.

5/16 drill bit.

A tire chuck is a device that connects to a compressor hose with 1/4" NPT threads and has a special head that pumps air through a schrader valve.

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Unread postAuthor: TurboSuper » Mon Dec 10, 2007 7:16 pm

Well:

-Avoid a ball valve if possible. Use a modified sprinkler valve instead.

-The chamber:barrel ratio is ideally 1:1 by volume, 2:1 is better though. Just use different diameter pipe to get the look you want.

-You can connect the support to the chamber externally with epoxy, that way no air will fow through it.

-You can get a tubeless tire valve (no threads), and pull the narrow end through a hole if you want to avoid using a threaded one. I don't see why, though.
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Unread postAuthor: Eddbot » Mon Dec 10, 2007 7:47 pm

where are you going to get 6" pipe? that's pretty rare, at least for me
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Unread postAuthor: schmanman » Mon Dec 10, 2007 7:55 pm

ummm.......

Dear Mr. Beaver,

it would be stupid to buy $40-60 piece of pipe just so you could use a piece. and my experience is that places don't usually sell it by the foot, or just sections of it, so you have to buy the whole thing.

so that part of your plan may not, or most likely will not work out.
even then, the pipe and fittings on the six inch would be many times the cost of the rest of the gun.

maybe go with 2,3 or 4 inch. the gun will look more like the diagram then, because the diagram is quite out of proportion

sincerely, schmanman.


I dont know why I just wrote that in letter form. :!: :D
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Unread postAuthor: DYI » Mon Dec 10, 2007 8:03 pm

The chamber:barrel ratio is ideally 1:1 by volume, 2:1 is better though. Just use different diameter pipe to get the look you want


Please don't hand out such horribly inaccurate information. Did you even use GGDT to get that, or did you just pull a random number out of the air?
At normal pressures, 0.2:1 C:B is ideal. After that point, lengthening the barrel will begin to have an adverse effect on performance.
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Unread postAuthor: schmanman » Mon Dec 10, 2007 8:14 pm

---------------------------------- ^
but making the chamber bigger can only help, and the only thing it will hinder is mobility.
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Unread postAuthor: Maniac » Mon Dec 10, 2007 8:36 pm

hollow out the tee and the place an endcap on the support part anthe hose clamp the tee to the suport srry if i cant explain right
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Unread postAuthor: LikimysCrotchus5 » Mon Dec 10, 2007 8:44 pm

Well schmanman thats debetable 8)

with a bigger chamber you get less pressure but more air and that is not necessarily better for a pneumatic cannon. Sometimes its better to have a smaller chamber to reach higer pressures faster.

But with bigger cannons, you cant really pump them up to high pressure (assuming its pvc) and it takes alot longer. But the reason why big cannons are awesome (work well) is that there is more air in the chamber that is under pressure, therefore more air to project the projectile out the barrel.

So it just depends on the cannon. But essentially, you will have the same amount of air in a smaller chamber at high pressure compared to a larger chamber at a lower pressure.
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Last edited by LikimysCrotchus5 on Mon Dec 10, 2007 8:48 pm, edited 1 time in total.
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Unread postAuthor: iknowmy3tables » Mon Dec 10, 2007 8:46 pm

wow for a second I thought flame the n00b for not searching, then I realized man you are so lost you don't know were to start, at least you know about taps, as a newbie I didn't

forget the support thingy and the gauge, (thats too many fittings to size it down to the 1/8" or 1/4"npt on the gauge) you better get a tap before you plan on doing that, go buy some rubber Schraders you, go to auto shop or some place were they do tires and ask for "a Schrader valve and stem for tubeless tires" you may have to pay them if they're greedy at most is $3, if there nice $0, my mom's a Costco member and the people at the tire center will give me handfuls of schraders if I ask, it should look like something like this Image you might not get the caps with them but that doesn't mater

for your first gun and apparently your first time with reducing pipe fittings I''' recommend you a simple inline design
4 foot barrel made from 1.5" pvc-- pvc male 1.5" NPT adapter --(remember teflon tape on threads) 1.5" pvc ball valve-- pvc male 1.5" NPT adapter -- a little length of 1.5" pvc pipe -- 1.5" to 3" pvc brushing (sch40 highly recommended) -- 3" pvc coupler -- 1.5 feet or more of 3" pvc -- 3" end cap -- drill hole for the rubber Schrader and push it in from the inside, you can add silicon sealent or jb weld to improve seal, take pliers and pull the schrader into position
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Unread postAuthor: schmanman » Tue Dec 11, 2007 6:16 am

LikimysCrotchus5 wrote:Well schmanman thats debetable 8)

with a bigger chamber you get less pressure but more air and that is not necessarily better for a pneumatic cannon. Sometimes its better to have a smaller chamber to reach higer pressures faster.



not always. you can take 6 inch up over a hundred psi, but most dont.


I was talking about at the same pressure. :wink:
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Unread postAuthor: TurboSuper » Tue Dec 11, 2007 8:07 am

I remember back on Spudtech people used to always say 1:1 was the best ratio, and it kind of tapers down from there. I couldn't really figure out GGDT so I never use it, too many fancy numbers and constants for such a simple idea.

I accidentally built my pneumatic with almost a 4:1 C:B ratio, it can fire pretty much twice in one charge, haha. Anyhow, it's still very portable :)
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Unread postAuthor: Mr. Beaver » Tue Dec 11, 2007 8:40 am

ty all, but with everything you guys said i thinking of just doing it all by my own, some of the stuff you said it's just 2 hard for me 2 translate.. :roll: ....
no justkidding but i think i have much more to learn, also about the costs i didn't tought i would cost me more then 40$ at start but now i guess it's pretty expensive also i need to buy the glues and stuff so with no one to guide me in my language it would be pretty hard.

i have to start reading more books......
can someone explain me some of the terms or actually shortcuts you use plz i now the C:B ratio it's not my problem i have more of a problem in the technical part

anyway i'm hoping to still ear from you guys on this post i learned some things now in this post :)
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