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Last few questions (hopefully) on my design

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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Last few questions (hopefully) on my design

Unread postAuthor: Hubb » Sun Feb 24, 2008 10:31 pm

I'm getting ready to start my pneumatic project, a pump action revolver paintball shotgun. In the original diagrams, I was going to use regulated CO2 to power it. Now, I'm considering going another route.

I've been looking at all the low volume / high pressure homemade pumps on here. They are some very nice (and cheap :wink: ) designs. I've never built one. What I'm thinking is making the launcher so that I can stroke it once (to work with the pump action part) and put at least 100 psi in the chamber. Now, the chamber would be about the same size (volume) as the pump, maybe 2 times as large. Is this possible? If so, any suggestions.

My next question; With a small volume pump, it's probably going to get hard to complete the pump. Is there a way to eliminate this, making it easier to stroke the pump?
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Unread postAuthor: lockmanslammin » Mon Feb 25, 2008 12:09 am

I may be way off here, as I am just a newbie in the pneumatic area, but I think if your pump had the same volume as your chamber that all you would do in one pump is double atmospheric pressure, which I believe would leave you with 14 psi in your chamber taking atmospheric pressure into account. Like I said Don't take this as a fact, I'm sure someone with way more background like Gipetto or someone will be able to give you better info. As far as it being easier to pump...... I drew a WAY simple diagram of how to use a lever to make it easier to pump...
I'm curious to see what others have to say...

Good luck, Lock
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Unread postAuthor: Hubb » Mon Feb 25, 2008 12:21 am

I like the lever idea. I was thinking of some type of pulley system, but this seems a lot easier to design.
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Unread postAuthor: Gippeto » Mon Feb 25, 2008 2:18 am

Sorry to be the one...etc.

Lockman has it about right, but it's not even that good. By the time you factor in cracking pressure of the check valve, your going to be lucky to get 10 psi in the chamber.

To get 100 psi in one pump, your pump cylinder is going to have to be roughly 7 times the volume of your chamber. That means (obviously) a cylinder which is either very long, or larger in diameter.

Do you have 7 foot arms by chance? :)

Didn't think so, the lever idea may provide enough force for the larger cylinder diameter. You'll have to crunch the numbers and see.
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Last edited by Gippeto on Mon Feb 25, 2008 6:46 pm, edited 1 time in total.
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Unread postAuthor: Hubb » Mon Feb 25, 2008 2:30 am

Gippeto wrote: Do you have 7 foot arms by chance? :)


Why, yes. Yes I do.

JK. So, to get my numbers started, I will need a pump that is about 7 times larger than the chamber, correct? I was thinking of making a smaller chamber as well, as I will want the rounds to travel at about 250fps.

I'll play with some numbers and see what I come up with. Thanks guys.
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Unread postAuthor: pizlo » Mon Feb 25, 2008 3:38 pm

If I'm not mistaken you the smaller the diameter of the pump the easier it is to finish the stroke, so even If you're chamber is very small It will be quite hard to make a single pump. If you make it two pumps before a shot then the pump can be half the size. Thats probably more feasible.
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Unread postAuthor: iknowmy3tables » Mon Feb 25, 2008 3:57 pm

I don't think a quick single or double pump is practical for any thing with a barrel over 3/4"

defiantly go with a regulated air source this only works with bbguns and even a single pump bbgun is hard to pump, I can't even imagine a single pump for a paintball shotgun
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Unread postAuthor: Hubb » Wed Feb 27, 2008 6:10 pm

You're right. With the numbers provided above, it would generate a launcher that is just too big for what I was looking for. The CO2 it is. I have my own bulk tank / fill station so it won't be too hard. I may even go with 12g or even those 88g cartridges. We'll see.

Thanks.
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Unread postAuthor: Hubb » Thu Feb 28, 2008 7:06 pm

Another.

I've contemplated backspin, however, the launcher will shoot 5 paintballs at the same time. I know, some will argue that it's not very practical. If I decide to go with backspin, would it be better to put the "spinner" near the muzzle or the breach?

Also, with a revolver design, is there a fast way of loading the cylinder that anyone could recommend? It's not going to open like a normal revolver handgun so a speed loader of that sort is out of the question.
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Unread postAuthor: Hubb » Fri Feb 29, 2008 2:33 am

bump
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Unread postAuthor: MrCrowley » Fri Feb 29, 2008 2:52 am

I would say breech for this case, because at the muzzle the front projectile may slow down enough for the one behind to bump it. I'm not sure how you're firing them, that would just be my first impression.
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