SpudFiles

Would a 6 inch long 1/2 diameter be sufficient to power a small hand pnuematic?

barrel?
Pressure?
desired muzzle velocity?
yoiu got some pretty vague specs there

Assuming you were using high pressure (250 psi +) and a fast valve you'd get decent power for a small calibre.

Well the barrel is about 8 inches.. I am prety fast with a ball valve. So I will use one. I will lube it up.. Thanks Guys!

ise a QEV if it is high pressure or a sprinkler valve if it is low trust me they can double the power of launchers that were at first useing a ball valve you just cant open the valve as fast as the pressure can but if you really want to use a ball valve I cant stop you it just wastes a whole lot of poteintial energy.

Nicely put bigbob!!!!!

I just posted "my newest valve" .Check it out they are very simple to build....and will improve your perfomance! 8)

Well... Done building it. The air resevoir is acutally the stock. And much longer. Just gotta wait 24 hours Pic up soon.

Why not make it a burst disk launcher?

potatoflinger wrote:Why not make it a burst disk launcher?

Well I am still Learning about Burst-Disks. I do plan on making one soon.

Well like I said I finished my gun and its good but the only problem is that the ball valve is slow. I know I said I am fast with them but I put it on backward so now I have to pull foward. I will spray some WD-40 down the barrel when its completly dry. I know people will say I should'ev put a sprinkler valve but wanted it to be a fast job. So what I am trying to ask is if there is anyway to make the ball valve faster.

There are ways to make ball valves faster, even fast enough to be useful if done properly. Me and Spudblaster had a short banter about that very issue one time. The essence of it is, if you could get a ball valve to open in less than 2ms, it would actually be better than a barrel sealer, because of less constricted flow. So here's my idea:

Construct a ram with the proper hinges to make it push the ball valve handle open. Get the ram body machined out of 2024 aluminum with walls a few inches thick, and an ID of about half an inch. Construct a piston out of titanium, high speed steel, tungsten, or something similar. Hook up a very strong rod between the piston and the ram that opens the valve, and put some O-rings on the piston. Put a stop on the end that the piston travels toward to stop the valve from being ripped apart by the kinetic energy of the ram. The stop could probably be 2" or so of hardened steel or titanium. Seal up the other end of the piston with a custom built endcap that has a built in high energy igniter, again probably titanium or similar. It'll need to take pressures of well over 100 000 psi, and massive shock loading, so build it strong.

To fire, simply pull the piston to the closed position, open up the endcap, and fill the space with some good ole' homebrew nitroglycerin. Put the endcap back on, load the projectile in the cannon, charge up the air chamber, and ignite the high explosive charge behind the piston. This should result in the ball valve opening so fast that by the time the air behind it can even move, it's fully opened, providing flow slightly better than that of a burst disk.

With some creativity, you could probably pull this off for under $ 2 000, if you have a lathe and good machining skills. OR, you could just build a piston valve for $20. Your choice

Hmmm.. think I will make a piston valve next time. For know WD-40 and a longer shaft on the ball valve will have to do.

Hi there counterstrike. I'm using a ball valve differently than you in that it will be used as the pilot for a piston valve rather than the primary valve, and honestly this is probably more work than you want to do, but I'm posting update pictures on a way of spring loading the handle so it will open faster. Honestly you should just do a little more research and put a piston valve on your cannon, but if your interested its under the topic heading "ongoing progress update pictures"

Good luck, Lock

You really should have just bought a Sprinkler Valve for $10. There's no point in spending $20 (or so) on something a third as good than spending $30 on something alot more powerful. Just because you can't wait doesn't mean you should blow all your cash instantly.

MaxuS the 2nd wrote:You really should have just bought a Sprinkler Valve for $10. There's no point in spending $20 (or so) on something a third as good than spending $30 on something alot more powerful. Just because you can't wait doesn't mean you should blow all your cash instantly.

I didn't want to do to much on this one. But now i regret it. I have more pieces and some cash, so I am going to remake it with Sprinkler.