SpudFiles

So I'm just getting into making spudguns, and so far have only made two.
This is my second one, and I tried using an electric valve instead of a manual one.







It uses a sprinkler valve, but I didn't mod it or whatever, i just wired a circuit for it. The barrel is mainly 2 inch Sch 40 PVC. The tank is 3 inch Sch 40 PVC which reduces to 3/4inch to fit the valve. It has a safety toggle switch to prevent accidental discharge, and uses a "soft-touch" button for the trigger. the whole circuit uses three 9v batteries for power, and has a built in pressure valve rated up to 100psi.
I have two interchangable barrels for different sizes of ammo. I use the 1-1/2 inch barrel to shoot easter eggs and pingpong balls filled with various things like rocks or airsoft BBs, and i use the 2 inch barrel for nerf rockets.

I'm posting this on here to see if anyone has any ideas for improving it to make it shoot straighter, farther, more accurately, or anything else to just make it a better spudgun in general

Also, there's a leak somewhere, because i fill it to 70psi and its usually down to 50psi in a minute or two. I'm not sure if this could be the sprinkler valve leaking, or if I should check all my connections.

Thanks for any suggestions for improvement, and if you want to see more pictures or anything, just let me know.
keep in mind this is my first post, i just joined today!

Not bad for your second. As for that leak, use water, or hand, your ear etc to find exactly where it's coming from. If it's a PVC joint, you can use glue or epoxy to seal it up. If it's the sprinkler valve, you'll have to troubleshoot it to find out why it's leaking:
http://www.spudfiles.com/forums/sprinkl ... t8780.html

As for better performance, try modding your valve:
http://www.spudfiles.com/forums/modding ... -t305.html

Or maybe even replacing it with a 1" valve, but you may as well leave that for your next cannon. A longer barrel always helps as well, you just need to find your your line between performance and practicability.

If you find some 1.5" SDR 21 (AKA Class 200) PVC, you can shoot golfballs with that. If you can't, you can always buy it online or just use a 2" barrel with wadding.

thanks, its been awhile since my first so i wasnt expecting this one to be all too good.
I'll definately try finding that leak tomorrow, and I should, with luck, be able to seal it up one way or another

as for modding the valve, thats out of the question because this is my dads valve, and he may need it back sometime so i dont want to completely ruin it.

and for barrel length, the longer the barrel the farther it should shoot and the more accurate it should be, correct? I'm mainly using this in airsoft games as a rocket launcher, so im just shooting nerf rockets. golfballs would be fun tho, i should definately try that (not in wars tho!)

also, i was wondering if there was any way i could charger this thing in the field whithout a bike pump or an air compressor. i have been researching 12 gram CO2 cartridges used with portable bike tire inflators, but it usually just fills the tank to between 40 and 50 PSI. if i were to make another tank, but make it smaller, would a CO2 cartridge fill it up more? possibly to 60 or 70?

thanks again for your help, im still new to this

Lots of ways in which you could improve this.

For starters, there's too much flow restriction for such a large calibre barrel. If you're stuck using the same valve, you should consider going to a smaller, longer barrel.

I would just get a larger valve and mod it if you're really after better performance. As to filling, nothing wrong with a good track pump, it will take you to 150 psi without much time or effort. Remember, a smaller chamber with higher pressure is always better in performance terms than a large low pressure chamber.

If you're feeling adventurous, you might want to attempt a piston valve. Not that difficult to build, will work out cheaper than a large sprinkler valve and offer vastly improved performance in terms of flow.

I have a 1-1/2 inch barrel that I also use. The problem for me is that I don't know what ammo to use with a smaller barrel that works for airsoft games. Thats the primary focus of this cannon for me; airsoft wars.

In the future I will definitely be attempting to mod a sprinkler valve, i just can't mod this one because, like i said, its my dads. I'll definitely look into a track pump. What stores would carry them? And about how much to the run cost-wise?

I really want to try a piston valve, but I don't exactly know how they work or how to put one together. Is there a forum somewhere on here that would help me out with putting one together?

>> all you need to know about piston valves <<

Good track pump, dirt cheap. Check cycling/sport shops if you don't want to buy online.

Wow I thought a piston valve was way more complicated then that!
I think I might start with a coaxial piston valve, because I already have two wrap around cannons.

But what do you think i should use for a piston in a cannon that has a 3 inch chamber and a 2 inch barrel? and how to i make the barrel go into the chamber, but still make it airtight?

Well it turns out I already have a pump like that, my parents ended up having one because they do triathalons and have all the expensive gear.
Whoops my bad, i should checked

If you want to know more about your valve, check the link in my sig.

As far as the launcher, I am definately a fan of the over/under with an anti-siphon valve. Just be cautious of the DWV on there.

I'm going to toss in my 2 cents worth.

First is a minor point. You don't need 3 batteries to fire the cannon. 1 or 2 work fine. The why is with AC you have inductance limiting the current. In DC you only have resistance. Lower DC voltage will provide the same current at much less voltage.

The second is in regards to piston valves. Yes they are simple with one moving part, but from there, it becomes an art to get them to work properly. A piston valve either leaks, sticks, has the seal blown down the barrel, or works. Sticking can be either friction, valve seat diameter to piston OD ratio, and/or eq port flow problems.

As mentioned earlier, the valve is way undersize for the barrel size. Much better performace can be had with a much larger valve.

i use a paintball regulator and tank but the last 2 times i tryed the glue was either wet still or there was no glue on one joint so it shot apart, now im scared that it will explode all my pvc is pressure rated to at least 280 and im only aiming for 120, but im really scared now

Hmm thats a good idea. maybe i'll re-wire some of the circuitry for just 2 battery's. thanks for the tip

i believe i have enough knowledge on piston valves, I've been researching some designs and i think i have a design that would work. I'm just really stumped on what to use for a piston. does anyone have any experience with a 2inch barrel and a 3 inch chamber? i have all the parts i need to start a piston valve launcher, minus the piston. so any tips on what to use would be greatly appreciated

Yes i knew from the beginning the valve would be too small for my purposes, but it was all we had around the house and I'm tight on money, so i just went ahead and used it anyways. if i had a choice i would've gone 1 inch or bigger (do they make those?)

But to everyone so far thanks for the advice, it really will help in the future when i make some more cannons. i plan on making at least 3 more