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Large Cannon Valve Ideas

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: bigbob12345 » Fri Dec 21, 2007 10:51 am

I say you should make the chambers 6in and the barrel 3in
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Unread postAuthor: DYI » Fri Dec 21, 2007 11:57 am

6" pipe and fittings are expensive, and difficult to obtain and assemble. As long as the barrel is 4" or less, a 4" chamber is fine, and cheaper.

Also, with a 4" porting valve, a 4" barrel gives higher performance than a 3" barrel.
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Unread postAuthor: bigbob12345 » Fri Dec 21, 2007 12:19 pm

How would a 4in barrel give higher performance. If you put a 3in barrel on it at the same ratio as the 4in barrel the projectiles in the 3in barrel would be going a decent bit faster. My rule with any cannon is that the barrel should be at least 1 step down in size from the chamber. And what can you even launch with a 4in barrel.With a three in barrel you can launch baseballs an if you have sch80 pop cans an pop bottles.
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Unread postAuthor: MaxuS » Fri Dec 21, 2007 1:06 pm

BigGrib wrote:
MaxuS wrote:
mopherman wrote:i Thing duel 2' sprinklers would be more than enough fro even a 4' barrel


I don't think that they make 2ft sprinkler valves.
I think two 2" sprinkler valves will do it, I've got one and the power is incredible, you could pilot them both with a 1inch version.


are you saying duel 2" sprinkler valves triggered by a 1" sprinkler valve triggered by a qev or a blowgun??


Duel 2" Sprinkler Valves, piloted by a 1" Sprinkler Valve, piloted by a blowgun.
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Unread postAuthor: Zippster » Fri Dec 21, 2007 3:02 pm

One trend I've noticed with all these valves and what-not is that the fastest are all practically different incarnations of the same thing: the chamber remains sealed off as long as pilot air at similar pressures is present. What is the real difference between the sprinker/piston/QEV's, in terms of lost pilot air, opening speed, affordability, and just general practicality? And does a modded sprinkler fill through the pilot just like a QEV/piston? That's a lot to ask, but some clarification would definitely help.
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Unread postAuthor: BigGrib » Fri Dec 21, 2007 3:11 pm

Zippster wrote:One trend I've noticed with all these valves and what-not is that the fastest are all practically different incarnations of the same thing: the chamber remains sealed off as long as pilot air at similar pressures is present. What is the real difference between the sprinker/piston/QEV's, in terms of lost pilot air, opening speed, affordability, and just general practicality? And does a modded sprinkler fill through the pilot just like a QEV/piston? That's a lot to ask, but some clarification would definitely help.


i believe, and now i have only made a sprinkler gun, that a sprinkler is the most affordable, a qev can be used to pilot faster than a blowgun, a piston is faster than both but more difficult to get to work right, i'm pretty sure
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Unread postAuthor: MaxuS » Fri Dec 21, 2007 5:03 pm

Yup thats right, I've made all three.
The Sprinkler Cannon was the easiest and most affordable to get working, and of course worked first time round with great results.
The QEV Cannon was a little more tricky because of all the threaded connections, but ended up working very well indeed.
The Piston Cannon was an utter f**king female dog to get working, if it wasn't one thing, it was another, and then if it wasn't that, it was something completely different.
So, for ease of use, go with the Sprinkler (and modify it).
For increased opening time, go with the QEV (a 3/4" one).
And for total satisfaction and increased performance, go with the Piston Valve (but do be warned that it can be exceedingly difficult to get working and may cause many sleepless nights).
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Unread postAuthor: Zippster » Fri Dec 21, 2007 5:31 pm

Again this is definitely one of those ultimate n00bish questions, but how much faster would a 1" modded sprinkler open compared to a 1" ball valve? And how much of a performance increase would it be to invest in a 3/4" QEV rather than the sprinkler? All I've ever had to compare to was that lubed ball valve - which I can get to open in lets say 3 tenths of a second - so arbitrary times compared to that would be fine.

On the same note, what would be the increase of adding an additional sprinkler/QEV to pilot rather than just a blowgun?
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Unread postAuthor: LikimysCrotchus5 » Fri Dec 21, 2007 6:13 pm

Well now noob :D , just as i was told before on this website and i have experimented with this, but not on purpose, a 1inch sprnkler valve compared to a 1 inch ball valve is this.

Ball valve - high flow rate, low opening speed
Sprinkler valve - low flow rate, quick opening speed

a 3/4 inch ball valve compared to a 3/4 inch modded sprinkler valve, a ball valve was better only because it had more flow when i used a 2 inch barrel. But generally sprinkler valves are better because of the quick opening times.

QEV opens faster than a spirnkler valve and its used as a pilot because the faster the pilot the faster the main valve opens.
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4SPC, My 4" piston 3" porting cannon
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Unread postAuthor: Zippster » Fri Dec 21, 2007 6:30 pm

Would I be wrong to assume that the whole low-flow issue could be easily remedied with simply getting a bigger valve? Or is there some other random 'who-the-hell-would-ever-think-of-that?' factor that I haven't heard of yet.

Edit: Victory dance - 25th post LOL! Least not a 1 star noob anymore...
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Unread postAuthor: LikimysCrotchus5 » Fri Dec 21, 2007 7:04 pm

no you would not be, but you can modify a sprinkler valve further and achieve higher flow rate and a stronger diaphragm as well.
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4SPC, My 4" piston 3" porting cannon
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Fix up copper cannon
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Start Stirrup pump
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Unread postAuthor: DYI » Fri Dec 21, 2007 7:51 pm

How would a 4in barrel give higher performance. If you put a 3in barrel on it at the same ratio as the 4in barrel the projectiles in the 3in barrel would be going a decent bit faster. My rule with any cannon is that the barrel should be at least 1 step down in size from the chamber. And what can you even launch with a 4in barrel.With a three in barrel you can launch baseballs an if you have sch80 pop cans an pop bottles.


You don't have GGDT, do you? Making the barrel an inch smaller than the valve porting with a reasonably fast valve wastes power by choking flow.
You can create durable Pykrete slugs for any barrel size you want, using materials that are essentially free (except the mould itself).

3" is a good barrel size (disposable oxygen cylinders filled with ice/concrete, pop bottles wrapped in tape, rutabagas, etc...), but having a cannon with a 4" valve, a 3" barrel is a waste of power. Certainly convenient, but as long as you have interchangeable barrels (which are absolutely necessary for continued enjoyment), you can always add a 3" one later.
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Unread postAuthor: Hotwired » Fri Dec 21, 2007 9:09 pm

:lol:

Remember, before you get carried away with ideas of massive (as in large mass) projectiles that you'll need to cushion the heck out of whatever the cannon is recoiling into.

That or make the cannon so incredibly heavy it barely moves on firing :)
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Unread postAuthor: MrCrowley » Fri Dec 21, 2007 9:21 pm

Hotwired wrote::lol:

Remember, before you get carried away with ideas of massive (as in large mass) projectiles that you'll need to cushion the heck out of whatever the cannon is recoiling into.

That or make the cannon so incredibly heavy it barely moves on firing :)


Something the mythbusters completely ignored with their grappling hook gun :D
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Unread postAuthor: DYI » Fri Dec 21, 2007 9:38 pm

Can't forget the recoil...
I don't really have to worry with the SCTBDC because the gun weighs >50lbs fully assembled, plus another 50 or so for the stand. The stand has started to loosen though, so I guess the recoil is getting to it.

A good idea if massive recoil forces are anticipated is to simply put wheels on the stand, so that the whole thing moves back on firing. That, combined with weighting it down with steel and/or concrete, should provide all the recoil absorption you need. Also remember, there are handheld rifles that put out >10k ft/lbs muzzle energy with no recoil absorption but the shooter.
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