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Design question

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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Design question

Unread postAuthor: EGOed » Wed Sep 26, 2007 4:59 pm

Well , I have been contemplating making a decent size cannon using 2 sprinkler valves similar to the configuration of the "Nuker II " that is being be sold for $750....... As I was looking at the picture of this cannon I noticed something that didnt make any sense to me......He is using two 1" sprinkler valves , yet he tees off the discharge of the valves using 1" piping ....Why bother using 2 sprinkler valves if you are only going to restrict flow back to 1" going into the barrell.....Shouldnt you upsize your discharge piping into the barrell when you run 2 valves to get increased flow rate ? I figured on using at the very least 1 1/2" tee and pipe with two 1" valves.
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Unread postAuthor: goose_man » Wed Sep 26, 2007 5:07 pm

Well, it's said that 3/4" QEV has better flow than a 1" sprinkler. Therefore, being generous and giving the 1" sprinkler a 3/4" flow rating, two would have a "flow area" of: 2 x (3.14(1.5/4)^2) = 0.883575 in squared.

Which means that if a 1" barrel is used, the barrel is not restricting the flow, the valves are.

-goose_man
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Last edited by goose_man on Wed Sep 26, 2007 5:08 pm, edited 1 time in total.
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Re: Design question

Unread postAuthor: jrrdw » Wed Sep 26, 2007 5:08 pm

EGOed wrote:Well , I have been contemplating making a decent size cannon using 2 sprinkler valves similar to the configuration of the "Nuker II " that is being be sold for $750....... As I was looking at the picture of this cannon I noticed something that didnt make any sense to me......He is using two 1" sprinkler valves , yet he tees off the discharge of the valves using 1" piping ....Why bother using 2 sprinkler valves if you are only going to restrict flow back to 1" going into the barrell.....Shouldnt you upsize your discharge piping into the barrell when you run 2 valves to get increased flow rate ? I figured on using at the very least 1 1/2" tee and pipe with two 1" valves.


What valve's of yours are going to be 1"?
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Unread postAuthor: LikimysCrotchus5 » Wed Sep 26, 2007 5:11 pm

Well it would be better to use a bigger sprinkler valve and you would have more airflow. Its best to go from bigger to smaller. For example, depending on what size of projectile you are shooting you would have a bigger barrel or smaller barrel. But it would also be good if you would have interchangable barrels. If you go from a big tank to a valve the same size and then a smaller barrel. More air would be forced into the barrel and would come out quicker because it opens faster and has more air so push into the small barrel and therefore you would have more air and more power into the barrel with a sufficient amount of speed. But also in a sense it can decrease the power by using a smaller barrel. It depends on alot of factors. Ammo is definately one of them and there are plenty more. Hope this helps
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Unread postAuthor: EGOed » Thu Sep 27, 2007 6:58 am

Well, what I am looking to do , instead of going to a single larger more expensive sprinkler valve , is run two 1" in parallel since I already have (15) 1" valves already modified for the various props and cannons that I use on my paintball field......Chambers are not an issue since I have several SCBA tanks that have been drilled and tapped to 1" , so I can run 2 of these in Parallel with a 1" sprinkler on each tank going into a single barrel.......My goal is to shoot mini 2" tennis balls as far as possible , so I will be using a 2" sch 40 pvc barrel which is a good fit for the ammo........Basically I am trying to figure out what size T to use to tie the (2) sprinkler valves into the barrell for optimum flow rate .... Should I just dump the (2) 1" sprinklers into a 2" T coupled to the barrel or downsize slightly to an 1 1/2 " T coupled to the 2" barrell.......Seems like I will have a little less dead space if I downsize the T slightly but I dont know how this will effect performance .
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Unread postAuthor: goose_man » Thu Sep 27, 2007 7:56 am

What you really want to do, in my opinion, is make sure that your barrel is the smallest flow point. In other words, with a 2" barrel, make sure that no part of the cannon before the barrel is less than 2".

Also, I'm not sure if you know this (forgive me if you do) but two 1" valves have less flow than one 2" valve. The reason is that the area that's opened with an ideal 1" valve is: 3.14(0.5")^2 = 0.7854" squared.
The area thats opened with an ideal 2" valve is 3.14(1")^2 = 3.14" squared.

Therefore, you would need four 1" valves to match one 2" valve. It doesn't scale linearly.

One more thing, those mini tennis balls that fit 2" sch40, are they the kind you get at a pet store? If not, where can I get some?

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Unread postAuthor: williamfeldmann » Thu Sep 27, 2007 8:30 am

You would need 4 valves to equal one 2 inch valve. But you can buy 4 valves for less than a 2 inch valve so why not.

I actually went through the work once of trying to find 2 inch valves and Lowes and Menards would actually order them for me for less than the internet, but I would still save like 10 bucks buying four 1 inch valves. You already have the valves = CHEAP.

If you really want power with the setup you have, use four tanks dumping into four valves. Tee the valves in pairs into 1.5 inch tees and tee the tees into a 2inch tee and your barrel. How many tees was that? :? Three

If you want a monster, buy yourself a 3 inch tee and make a piston (probably barrel sealing seeing your tanks). You are going to be limited by the flow out of your air tanks since they port 1 inch.

@Goose
You should be able to find those smaller tennis balls at a place like Petsmart, ask for small dog fetch balls. They are very popular for people who have smaller dogs like rat terriers. I have also found them at Super Walmarts, but you can buy them in bulk at Petsmarts.
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Unread postAuthor: EGOed » Thu Sep 27, 2007 9:32 am

Great , thanks for the help guys......You know I was thinking I would be better off going to a piston valve , but I wasnt sure how well they would last with frequent usage and can they be made to easily replace worn parts like rubber sealing gasket . I see some piston valves are made with screws holding the back pilot bushing into the T ..... Is this so you can access the internals to replace parts or is it solvent welded here also................. I bought the dog fetch balls at Wal- Mart.
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Unread postAuthor: williamfeldmann » Thu Sep 27, 2007 9:50 am

A piston valve will last almost indefinetly with maintenance. The back cap is almost always screwed in instead of glued, this provides easy access to the piston for replacing parts or cleaning, or whatever. They use orings to seal up the back inlet/pilot port area, and teflon around the screws.

There are quite a few piston valves out there to look at. Some are longer than others, some you can buy. Unfortunatly, no-one has posted a detailed planset on here for making one, or I haven't found it yet.

One of the best built valves I have seen on here is a 2" called the Slayer Valve by Noname, the post has good pics.
IPaintball has another seen here with pics. There a quite a few valves on here. Check them out.

The good thing about a 2" tee is you can get all the parts at your Lowes, etc. store instead of going to a plumbing specialty store.
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Unread postAuthor: goose_man » Thu Sep 27, 2007 11:35 am

williamfeldmann wrote:@Goose
You should be able to find those smaller tennis balls at a place like Petsmart, ask for small dog fetch balls. They are very popular for people who have smaller dogs like rat terriers. I have also found them at Super Walmarts, but you can buy them in bulk at Petsmarts.


Thanks!

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