Yes, I know. Don't start a new thread as your first post, but I searched and could not find any info on my question. Well, I designed a bolt action pneumatic spud gun, with a bolt that moves back, instead of the whole barrel moving forward (the designs for that can be found with a google search), so that I can quickly change barrel sizes without switching out the entire bolt. I'm planning on using an extra CO2 tank from my paintball gun as the air source, eliminating the need to pump up the tank after every shot. My only problem is that I need an electric valve strong enough to withstand the pressure of CO2. I believe the psi is somewhere around 1100 on a full 20 oz. tank. The valve needs to be fairly small so I don't have to completely re-design the layout of the components. Something in-line and smaller than a standard 1" solenoid sprinkler valve. Any comments/suggestions would be greatly appreciated.

1100 psi sounds like a lot of pressure for a spud gun. Copper pipe only takes around 850 psi with liquids and 200 psi with gases. Why not use a regulator to take the pressure down, and then use a solenoid valve that will work with lower pressures?

You could also take a look at http://cambriabike.com/SALE/pumps/index.htm

They sell a 40 gram CO2 tire infalting device that will fit onto a schrader valve. This way, you can use the cartridge to pressurise the reservoir on your gun inbetween shots. Also, as the CO2 system can be turned off between shots, so that you don't lose extra gas when the solenoid valve is opened (although this depends on the timing of your valve system).

While we're on the topic of spud guns, what sort of ammo do you use? I find that an empty 7.62 mm cartridge that has been refilled with lead :D requires only minimal wrapping with masking tape to form a good seal in a 15 mm barrel. It also has a fairly good amount of power (although the rounds tend to tumble through the air but that's what you get from a smoothbore barrel).

There is an existing topic on this subject at http://www.roguesci.org/theforum/showthread.php?threadid=725

I agree, you don't want to be putting full bottle pressure into your gun, get a reg!

High pressure solenoid valves are not easy to find, to the point where people have found it easier to make them from scratch than source them. Hydraulic solenoid valves can be used, they're fairly cheap and will easily habdle the pressure, but being designed for viscous liquids, not gases, they can leak all over the place.

Thanks. I decided to use a Palmer reg (paintball) on the tank so I could use a Rainbird solenoid, they hold up around 120 psi. As for ammo, I usually get a length of pipe the same diameter as my barrel, sharpen the edge of one end, cut slugs, and freeze them. If you get a pack of cheap pencils, and pull the eraser/metal part off, get one of those pins with the little ball on the end, and put about 10-15 peices of yarn on it, and shove the needle through straight, starting from the bottom of the eraser up, it makes a nasty little dart that flies pretty stable, they fit 1/2 in. barrels. And thanks for the link to the other thread. I had pretty much figured out that using CO2 to charge up a PVC tank was probably a bad idea in the first place though, so I went with the idea of just hooking up a paintball tank to a high-rated solenoid, but didn't think of a reg. Now all I have to do is wait until I have enough money...

The other way to do this is to use a reg to produce a low pressure supply, then use a low pressure solenoid valve to drive a high pressure pneumatic valve. Its a common industrial master/slave arrangement.

Hmmm this master/slave valve setup sounds intresting but totally confuses me on how it would work. Tuatara can you explain in a little more detail how this type of setup works? I will do some research into this as it sounds very intresting as I have always wanted a high pressure pneumatic cannon to play with :D

I have thought of making the popular piston disign that is used with most high pressure pneumatic spud guns but these require a ball valve and I want one that uses a high pressure solenoid valve. I haven't disigned my gun yet but if at all possible I want to run it off of somewhere around 200psi maybe 250psi but if I go that high I will need some serious equipment to manufacture it as it will need to be Al.

I'm hopeing to get this thing designed and build by spring so I can do some fun testing with it.
If I can I might even see if I can get a rifled barrel attachment made for it along with some other barrels for different purposes.

Any help would greatly be appriciated Ideas are always welcome as I really haven't been working on the design much lately. Any suggestion and/or tips would be very helpful.

Well, my last post was a little terse, I admit.
What I'm trying to describe is a system in which there are two gas supplies, one high pressure and one low pressure. The low pressure supply is used for control gear. In a pneumatic system it is possible to do everything with air pressure - you can get swtiches, one-way valves, multi-port valves, proportional valves etc. The switches generally run on low pressure, (for operator safety as much as anything), an these low-pressure 'signals' can be used to operate pneumatic valves which control high pressure air - to do whatever e.g. drive rams.

So instead of using a pneumatic switch, I'm suggesting using a solenoid valve to provide the low pressure signal to operate a pneumatic valve which controls the high pressure air.

If you register you can get loads of power-point based pneumatic training guides free from Norgren (http://www.norgren.com/)

Thanks for all the help. I have this thing completely designed now. I was hoping I wouldn't get flamed for having a new topic as my first post, and I guess I'm just barely not-lame enough to have pulled it off :D . Chemical_burn, on the topic of rifled barrels, wouldn't somehow attaching a drill bit slightly larger than in id of your barrel to a swivel on the end of a rod, and pushing it through with a constant speed, create a crude rifling? Since it wouldn't be going fast, I think the cut would just follow the same pattern of the bit, although I could be wrong.

OK...this thing has officially been built. I used the tank from my old cannon, I can't afford to make it CO2 powered yet. No wood stock either, I don't have the proper tools here, I need my grandfathers shop that's all the way in Mississippi. I'll try and get pics of the bolt assembly up tomorrow once the PVC glue sets. My dad and I designed some exploding rounds, too. Pretty simple, sort of an improvement of the kewl bb-glued-to-a-shotgun-primer thing, but it should be pretty reliable.

You can work out roughly how many twists are needed for your barrel using the Greenhill Formula:

Bullet Caliber (K ÷ (Bullet Length ÷ Bullet Caliber)) = 1 twist in so many inches (round down to the next whole number).

All dimensions have to be in inches.
K is a constant and is equal to 125 for velocities up to 1500-fps, 150 for velocities of 1500-fps to 3000-fps, and 180 for velocities of 3000-fps and up. From what I've heard, most air cannons work at around 500-fps but I haven't used a chronometer on mine yet.

http://www.aeroballisticsonline.com/ballistics/riflings.html#greenhill

The spudder's super supply source: McMaster Carr (http://www.mcmaster.com) This is a great site they have everything you could possibly want (except SDR21 1.5" pipe aka golf ball barrels). Search for Quick Exhaust Valve they are very useful for actuating piston pnumatics.