New cannon

[schismatized]

Yeah so this is my first post here at this site, but i have been building spud guns since '02. I was a member and lurker of the spudtech forum for a long time. Anyways.. Ive decided to build a new gun and i haven built one in about 6 months or so. Itll be my first **hopefully** successful piston cannon. Here are the rough specs:
10' x 1.5" barrel
6' x 4" chamber
The valve will be built in a 4" tee and be triggered by a 1" sprinkler valve. I was thinking of using this valve construction but i am open to suggestions really. The valve is the whole point of my post.. Im just kind of winging it. Anyone got any ideas or pictures of their piston valves that i can see? That thread wasnt too clear but i get the general idea. Im having trouble finding the "rubber donut" to go in my tee.

[jrrdw]

Welcome to spudfiles, it's nice to see new member doing research before asking. I know you said you are building in a tee, but maby you can get a good idea out of mine -- The Basterd, it's ugly but works good. Click on 'action' below the pics to see a short video.

[schismatized]

Wow you got a nice cannon there man. The only reason i was building in a tee is bc i really dont want to do much "customization" to my fittings.. I just want something that can pretty just glues together but thanx for the idea haha. BTW you better be careful shootin that thing in your shop haha.

[schismatized]

Oh BTW i was wondering what do you guys think of this: So i set this gun up on GGDT. It has the 4 in valve and everything. So when i have a 1.5" barrel on it, with a 200g object, its says 471 fps and the external ballistics says 2203ft and it says Barrel is chokin flow. SO i up it to 2.5" and keep the rest of the stats the same (i correlate the projectile size). NOW it reads a higher fps:628 but a lower distance at 1344ft. How come? My barrels are going to be interchangeable but all i have the money for right now is one and IMO 1.5" is all around good for spud shootin and random things. Should i change to a larger one?

[Velocity]

If you are using a 1.5" barrel... then you definitely want to reconsider your cannon.

For one, I would build the piston valve in a 2" tee instead of a 4" tee. It will be much cheaper and it will yield much greater performance as well.

A 3" x 60" chamber will give you a 2:1 chamber to barrel ratio, which is very good. Using a 4" x 72" chamber will give you a 4.27:1 chamber to barrel ratio, which is very inefficient. It will not increase your performance significantly, and it will just be a huge pain to fill up.

[schismatized]

well i can buy all the fittings for the valve for about forty dollars. but i do see your point on being a pain to fill up. Also, a 3 in cap fits inside a 4 in tee- pretty good piston. Last time i tried to manufacture my own piston it didnt turn out well. any suggestions on how to build a decent piston? last time i tried to build it out of would and ran into a whole slew of probs...

[frocksie]

House the piston in a 2in Tee, and buy some solid PVC stock. It is pretty heavy, but if you drill material out of the back, it is a great piston that is very easy to use. It was my first piston valve, and worked on the very first shot.

[schismatized]

House the piston in a 2in Tee, and buy some solid PVC stock. It is pretty heavy, but if you drill material out of the back, it is a great piston that is very easy to use. It was my first piston valve, and worked on the very first shot.

that rod is reaaallly expensive. wheres the cheapest place to get it? also, anyone other suggestions for pistons.. i may go with a woody like jrrdw said. Basically, this cannon will just be made to shoot things a long distance. i really dont care about velocity..

[schismatized]

anyone got any other suggestions? I think i am going to be switching to a 3in tee and a 2 in barrel. i crunched the numbers and it looks very nice

[Bubba05]

Yeah that sounds kewl mate just got to get the reducier down pat

Bubba

[spudthug]

bubba what the hell are u talking about!! your going around making stupid ass posts about nothing! u dont even read the whole thread u jsut read the last post and post something useless!!! freeking post whore!

@sch- is this cannon going to be handheld??

if it is its going to be pretty hard to shoots without falling down

you could use a 4" valve to a 2" port? that wont decrease performance will it? it will probably increase it..plus you have access at an easy piston

(3 inch end cap)

[rednecktatertosser]

If you use a 2" tee a 1.5' endcap works great as a piston.

[schismatized]

anyone know what would make a good piston for a 3in tee?

[schismatized]

also, how much better performance would i get by using a 3in x 2in Reducing Coupler instead of a bushing for the barrel?

[schismatized]

anyone? surely somebody has some input here? or is that question worthy of its own post? in the past, i have always used bushings, but a 3" x 2" reducing coupler seems like it would have much better flow. is it worth and increase of like 10+ dollars?