Pneumatic Golfball Cannon- Shoots 450+ yards!

Step 3 Modding The Sprinkler Valve

Here I will teach you how to modify the sprinkler valve for pneumatic actuation.

You should find all the materials at Home Depot.
You'll need a:
1" sprinkler valve
1/4" brass nipple
1/4" blow gun
Epoxy
Teflon tape

Step 1:
Take all the screws out of the lid from the sprinkler valve and then pull the lid off. Leave the rubber diaphragm in place and make sure you don't lose the spring.

Step 2:
Get a drill bit that is slightly small in diameter then the brass nipple and drill a perfect hole in the middle of the lid from the sprinkler valve. Put some teflon tape on the brass fitting and thread your blow gun on, make sure to remove the nozzle from the other end if it has one.

Step 3:Thread the blowgun with the brass nipple into the hole, make sure to do it slowly and perfectly straight. Remove the solenoid (big black thingy) from the sprinkler valve. Mix a small amount of epoxy and clog up the hole where you just unthreaded the solenoid from.

Step 4:
That's it, just leave it to dry.

The sprinkler valve will be used as the pilot valve for the piston. You could get away with a 1/2" ball valve instead but this will give you more power. Any problems with the valve, read this:
http://www.spudfiles.com/forums/viewtopic,p,95154.html#95154

Comments

[Pizzapie500]

I'm going to post a vid on how to do this b/c it seems a lot of people have issues. (Actually I already made it, I just didn't post it.) Also Sprinkler Valves are only meant to go to 90 PSI. Well, at least, mine says that on the box. Lastly, do you have any problems with threaded parts? I wrapped mine in 4 layers of teflon tape and it still leaks. I heard that you should use gas teflon tape, but i'm using the regular ones that come in a blue thing.

[MrCrowley]

Mine says 125PSI but it doesn't matter anyway, they're probably good to 200PSI. Blowguns are only rated for 90PSI but can be good to 700PSI.

I only have problems with brass threaded fittings, just wrap them in more layers and insure the threads are clean. The gas teflon is just normal stuff but thicker pretty much.

[Pizzapie500]

Oh whoops. You're right! I meant that my blowguns are only rated at 90 PSI. Also should I get gas teflon tape? It's sort of expensive considering that regular teflon is 30 cents and gas teflon is $3.50

[grevious]

hey man it would help alot if you show us a picture of the inside of te sprinkler valve, i get the general idea but i dont know what some of these fittings your talking about are, such as the brass nipple, never heard of this before?

[MrCrowley]

The inside of a sprinkler valve doesn't really matter, seeing as you can buy them commerically, and modding them is so easy and requires little knowledge of the sprinkler valves operation. It shouldn't matter. It's pretty much just a barrel sealing piston valve but it uses a diaphragm (sheet of rubber) instead of a piston. A brass nipple is just a threaded brass fitting. These descriptions are widely available on google, i'm not going to write out everyone. If you don't know them, then you shouldn't be building this yet sorry.

[grevious]

well prior to finding this page on instructables i had looked at a few videos and a few descriptions and it does seem rather easy. at the moment i only have a simple combustion cannon and would like to go up to a more greater power. and i cant work out what is safer? combustion or pneumatic? combustions have a sudden impact pressure on the chamber that would cause stress on it yet, yet a pneumantic has built up pressure for longer, and a pneumatic reachers higher psi thatn combustion, but yet i still dont know? you wanna help me out lol?

[MrCrowley]

Some say combustion, some say pneumatic. If you stick to below 125PSI and you use pressure rated components, it should be perfectly safe. The lowest pressure rating on the cannon is probably the sprinkler valve, at 125psi. But you can easily take them above 150psi no problem. The pipe is rated around 200-300psi, depending on the fitting/pipe diameter and brand. Though I would never condone taking PVC above about 175psi, it's just too dangerous. Either way, combustion or pneumatic, you should be safe if you build it right.

[grevious]

most people say that you should never take the psi above half of the pressure rating because there tested with air right?

[MrCrowley]

I think you mean because they are tested with water. Which is no different to air, aside from it transfers less energy if the PVC pipe fails, the shrapnel will travel slower. But with PVC, I wouldn't advise going above half the pressure rating like you say. With other materials you can go well over, it really depends. QEV's rated for 150psi, can easily take well over 500psi for example.

[grevious]

oops i didnt realise i typed "air", my mistake. and yes i realise that most things rated say 250psi, actually would be up at 300 and just downed to 250 for safety reasons, yet i wouldnt take it above half of it for safety reasons anyway.

[pufferfish9108]

also if you pressurize it and then released it fast enough it helps. it would be cool if you did it with water!!

[nononame]

is it possible that the blowgun valve you put on top of the sprinkler valve leaks? cuz mine seems like it does. help?

[MrCrowley]

Mine does not leak. Either, yours is upside down, faulty, you drilled the hole too big, you didn't use teflon tape or you didn't use a tap to make threads in the hole. If any of these apply to you, then change whatever accordingly. If you've drilled the hole too big, drill a bigger one and use a 3/8" fitting, then an adapter to make it 1/4" male threads.