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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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Unread postAuthor: theBOOM » Mon Aug 23, 2010 9:29 pm

Rag is write, bigger is not always better.. or in this case too big isn't always better, plus the fill time on a 60 gallon chamber wouldn't be pretty. I'm sure you'd be more than fine with a 30 gallon chamber.
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Unread postAuthor: velocity3x » Mon Aug 23, 2010 10:36 pm

Jimmy K wrote:For a chamber I was thinking of an old 60 gallon vertical air compressor tank. So you're saying that would be too big? I want power and it just seems like a 30 gallon tank wouldn't do it for me. Am I wrong?


I think a 2 gal. chamber would be more than ample for a 5" x 10' barrel.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 7:00 am

Ok so far:

10' SCH 10 aluminum barrel;
11 gallon chamber;
2 2" Mauler valves;
1 Hydraulic cylinder;
And some random junk that I have in the barn.

Am I missing any crucial parts?
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Unread postAuthor: c11man » Tue Aug 24, 2010 9:24 am

velocity3x wrote:
I think a 2 gal. chamber would be more than ample for a 5" x 10' barrel.


remember what kind of pressures we are working with. low pressure needs higher volume. i use a 8 gallon chamber with a 3inch by 15ft barrel
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Unread postAuthor: skishoot » Tue Aug 24, 2010 9:24 am

You are going to modify the chamber to have a bigger output right because if you don't it will be equivalent to having a 1/4in npt valve and it wound decrease range a ton, and it would deplete the purpose of having 2 2in valves.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 9:53 am

skishoot wrote:You are going to modify the chamber to have a bigger output right


Yes. I am going to cut out a large circle and have a friend weld in a pipe and flange for mounting.

And c11man: what kind of pressure are you putting in that chamber?
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Unread postAuthor: Technician1002 » Tue Aug 24, 2010 10:03 am

c11man wrote:
velocity3x wrote:
I think a 2 gal. chamber would be more than ample for a 5" x 10' barrel.


remember what kind of pressures we are working with. low pressure needs higher volume. i use a 8 gallon chamber with a 3inch by 15ft barrel


I use a 3 gallon chamber with a 7 foot 3 inch barrel. At higher pressure, the chamber is a little large. It is most effecient at about 35 PSI. I'm planning an 8 gallon chamber for a future 4 inch launcher with a 4 inch port valve. I would go with a larger chamber if considering very soft projectiles and pressure under 30 PSI.

I do agree that using a larger port on the chamber is worth the effort. :D
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 10:19 am

4" valve? They make those?
I just did a little math, and 2 2" valves is still only about half of the cross sectional area of the barrel. So it seems like I won't be able to get maximum flow through the barrel unless i had a 4" ball valve squished between the chamber and barrel. But then it's super gradual release compared to the Mauler valves.
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Unread postAuthor: Ragnarok » Tue Aug 24, 2010 10:36 am

Technician1002 wrote:I use a 3 gallon chamber with a 7 foot 3 inch barrel.

Which, we have to remember, is only 40% of the volume of a 10 foot 4" barrel.

~~~~~

I think an 11 gallon chamber will do the job very nicely - it's about ~1.6:1, which is probably about all you can really hope to really make use of.
Like you've just said, even with two valves, flow is going to be reasonably limited compared to the 4" barrel - however, that's not a huge problem. It means you wouldn't be able to make much of a larger chamber, but in this kind of cannon (large bore, reasonably heavy projectile) having maximum flow isn't as important as it normally is.

And no, they don't normally make 4" valves. I imagine Technician1002 will be making it himself.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 11:10 am

Ragnarok wrote:but in this kind of cannon (large bore, reasonably heavy projectile) having maximum flow isn't as important as it normally is.


By your same logic, could it be said that a quarter turn 4" ball valve would be as effective as 2 2" valves?
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Unread postAuthor: Fnord » Tue Aug 24, 2010 11:11 am

4" valve? They make those?
I just did a little math, and 2 2" valves is still only about half of the cross sectional area of the barrel. So it seems like I won't be able to get maximum flow through the barrel unless i had a 4" ball valve squished between the chamber and barrel. But then it's super gradual release compared to the Mauler valves.


Did you guys even look at the link I posted on the last page?

If you still want to buy mauler valves to support the site that's good, but if you're concerned with power go with the irrigation valves.

Edit: If I were you I'd message the guy selling them on ebay and ask for more pictures of the broken one.
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Last edited by Fnord on Tue Aug 24, 2010 11:53 am, edited 1 time in total.
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Unread postAuthor: Ragnarok » Tue Aug 24, 2010 11:45 am

Jimmy K wrote:By your same logic, could it be said that a quarter turn 4" ball valve would be as effective as 2 2" valves?

Ha ha. No. I'm talking more about flow area, than valve speed. When valve speed is involved, I'd never choose to skimp on it.
Also, a quarter turn on a 4" ball valve doesn't add up to the flow area of two 2" valves.

You could do well to chase down something like Fnord linked, but I'd personally reckon on two Maulers having the edge on that one. (Piston valves tend to have a higher flow efficiency than irrigations valves, so even though they have a slightly lesser cross sectional area, they'd probably still pass air quicker.)
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Unread postAuthor: Technician1002 » Tue Aug 24, 2010 11:55 am

Just for those who think 2 2 inch valves will replace 1 4 inch valve, Draw a 4 inch circle on paper. Now draw 2 2 inch circles side by side inside the 4 inch circle. Now paint the area inside the 4 inch circle that is not inside one of the 2 inch circles. Lots of black? you bet. 2 two inch valves have half the cross sectional area of one 4 inch valve. The 4 inch valve will have less surface area to drag on the flow for a better flow coefficient and won't have to use a couple of t's with the bends to further restrict the flow.

This ends my valve 101 class for today. I plan on building my 4 inch valve. In those sizes for speed and flow, butterfly valves or piston valves are common and either will outperform 2 mauler valves in parallel. A single 3 inch valve has a great chance of being better. A 4 inch orifice piston would be killer.
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Unread postAuthor: Fnord » Tue Aug 24, 2010 12:13 pm

Technician1002 wrote:...This ends my valve 101 class for today.


So, in conclusion, 2+2 = 2.828427...

There. It's settled.
:)
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Unread postAuthor: Technician1002 » Tue Aug 24, 2010 12:22 pm

2inch valve 3.14 sq inches
2 2inch valves 6.28 square inches
3inch valve 7.065 square inches
4inch valve 12.54 square inches

I vote for a single 4 inch valve to feed a 4 inch barrel. :D
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