Easy to Make Piston Valve Air Cannon
Update: So I recommend you instead follow my newer how-to as it is far more updated and I am far more experienced, the information used in this guide can also be found in my new one located here: Thanks.
I've recently made a far better how-to that covers two different piston designs, aside from that the animations and pictures are also of higher quality and more accurate then the ones I have used in this how-to.
http://www.instructables.com/id/Golfbal ... That-Shoo/
I know this isn't perfect but I figured since I spent the time to put it on that site may as well have it here for some extra info and help.
[youtube] [/youtube]
This is my golfball gun, it features a 2" barrel sealing piston with 1.5" porting. The chamber is made from 2" Pressure Rated PVC pipe and the barrel is 1.5" PVC pipe. For more information go to:
http://www.spudfiles.com/forums/viewtop ... tml#100616
Note:
One shot I am firing into the open, I was shooting a golfball 380m at a golf course that was closed due to weather 50m away.
Step 1: How the piston works
1) Air is sent through the inlet valve, this pushes the piston(green) forward and sealing the barrel, the air leaks around the chamber and fills the chamber up.
2) Once the air is equalized all around the chamber and valve, the inlet valve is closed.
3) When you want to fire, you open the pilot valve and all the air behind the piston(pilot area) vents out this valve, since the pressure on the piston is un-equalized with more pressure at the front pushing it back, then pushing it forward the piston actuates.
4) The piston flies back at incredible speed and all the air goes out the barrel and launches the projectile.
Step 2: Parts
All you need to make a more basic version of this is:
*3" NSF-PW Sch40 PVC(chamber)
*1.5" SDR 21 PVC(Barrel)
*3" NSF-PW Sch40 PVC end cap
*2" NSF-PW Sch40 PVC End Cap
*2" NSF-PW Sch40 PVC tee
*3"-2" PVC Bushing
*3" NSF-PW Sch40 PVC 90* elbow
*3" NSF-PW Sch40 PVC 6" long pipe x 2(these join your fittings together)
*2"x1.5" NSF-PW Sch40 PVC bushing
*2" NSF-PW Sch40 PVC 3"x1"
female threaded bushing
*1" threaded ball valve
*1"x1/4" bushing
*1/4" quick connect(for air compressor)
PVC Glue
PVC Primer
Common Sense
Deodorant Can(for your piston)
Neoprene sealing face.
Step 3: Piston Construction
To make a piston for a 2" PVC tee all you need is:
*Deodorant can
*Neoprene rubber gasket(found in plumbing section, this is your sealing face)
* Suitable bumber
*Hot glue
Now cut the bottom 3" of your deodorant can, cut up some hot glue sticks, chuck 'em in there and melt them. Now your piston should be about 1/2 full with glue for reinforcement.
Drill a hole the size of your long bolt through the bottom of the can and through the glue, grab a washer that fits the bolt, put it on and then put your sealing face on the bolt with the washer on top.
Now thread the bolt through the hole in the cane and through the glue, it should come out on the other side, now find something thats soft and bouncy or rubbery as your bumper, this protects your tee from the piston breaking it when it fires back.
Put your bumper on the bolt and stick a washer on and then a nut, tighten the nut and thats your piston done.
In the picture below I had to seal the top of the sealing face because air leaked through the piston a bit.
The bottom of the piston in the picture is my bumper.
Step 4: Piston Housing Construction
Now you have two options:
1)Servicable piston housing(incase it breaks you can open it up)
2) Non serviceable piston housing(if it breaks your screwed)
I recommend the first option, now to achieve this you are going to need to cut a length of 2" Sch40 PVC pipe so it goes all the way inside the tee and hits the 'lip' inside the tee, now cut the pipe so it has about 7cm of pipe coming out of the tee, so the pipe would be around 15cm in total length.
With the 7cm of pipe coming out the back of the tee(which is your pilot btw) fit your end cap on it, if when fitted on there is still pipe visable between the end cap and tee, cut the piece of 2" pipe(the 15cm long one) so there is no pipe when the end cap is on fully.
Now with your end cap on, grab four screws that are long enough to go through the end cap and piece of pipe but still long enough the stop the piston when it moves back. So a screw thats about 3cm long should do.
Drill four holes evenly around the end cap and through the 2" pipe which its on, so you should have 4 holes, one at 12 o clock, one at 3, one at 6 and one a 9.
Now thread the screws in to make the threads in the pipe. Now remove the end cap, screws, 2" pipe, we will glue it later.
Step 5: Pilot Setup
Okay now you need your pilot valve and inlet valve.
The inlet valve you hook up to your air compressor, to fill the chamber up.
The pilot valve vents the 'pilot area' and actuates the piston which fires the gun. For this I recommend a 1/2" ball valve.
How you set this up is up to you but the basics what you need are:
1/2" Brass tee
1/2"-1/4" brass bushing
1/4" metal ball valve
1/4" quick connect(inlet valve)
1/2" metal ball valve.
1/2" brass nipple x 2
Using teflon tape thread one of the brass nipple in the bottom of the brass tee.
Still using teflon, thread the other nipple into one of the other ends of the brass tee, now thread your metal ball valve onto the other end of the nipple(this is your pilot valve).
Now teflon up your 1/2"-1/4" bushing and thread it in the final port of the brass tee, now thread your 1/4" ball valve in here and then your quick connect(this is because a QC doesnt have a valve and once disconnected will just let out air, the ball valve when shut will stop this)
Once everything is thread and working, drill a hole in your 2" end cap from the back of your piston housing. Thread the brass tee with the nipple into this and your set.
Step 6: Barrel Setup
When cementing and priming the barrel into the tee(which I will explain later) the barrel needs to extend through the bushing and into the tee like the picture below.
That pretty much explains it, you just need to modify the bushing so the barrel can extend through it.
Step 7: Construction
Okay....
Drill a hole in your chamber for a pressure guage and thread it in and then....
Grab your chamber of 3" pipe, a 50" chamber will do.
Prime the pipe at one end, prime your 3" end cap, then glue the end of the chamber where the primer ios and do the same for the end cap. Stick it on and hold for 30sec.
Get one of your off-cuts of 3" pipe and prime and glue to the other end of the chamber so about 3" of pipe is still sticking out the end of the chamber, prime and glue your 3" 90* elbow onto this.
Prime and glue your 3"x2" bushing into the other end of the elbow, then prime and glue it to the bottom of the pisotn housing(tee)
Shove your 2"x1 1/2" bushing over your barrel so when the bushing is primed and glued into your tee the barrel should extend isnide the tee half way like in the picture in step 6.
Once you have sorted out this, prime and glue the bushing to your barrel, then prime and glue the bushing(with barrel on it) to the front of your tee.
Lube up your piston and isnide of the tee, chuck it in there and stick on the end cap which you are going to bolt one. DO NOT GLUE IT! Now that your end cap complete with pilot valve and etc out the back of it, is on your 2" pipe which is connected to the tee, line up the screw holes and screw them in.
Personally I use screws like this but with an allen key head in them: http://www.explorerforum.com/photopost/ ... CN5937.JPG
Okay, thats everything I think, just wwait 24hours for it to dry and test it out. The piston will probably require either intense pumping from a bike pump or about 15psi from a compressor to seal, I can get mine to seal at 7PSI and shoot at 10psi.
I recommend not taking the gun over 130psi for safety reasons.
Done:
That just about does it. Make sure you prime the pipe first then glue it using PVC solvent, just read the label on the back and you should be fine.
How you set up your piston is up to you, if you want it serviceable or not etc. Just drop into spudfiles.com for more help.
'''Disclaimer:
If you hurt/injure/kill yourself/someone else, while making this pneumatic gun I am not liable. By using these instructions you are making this at your own risk. Make sure you know exactly what you are doing first. '''
SGA Cannon: http://www.spudfiles.com/forums/viewtop ... tml#100616
Source: https://www.spudfiles.com/viewtopic.php?t=10381