Introduction: Pneumatic Golfball Cannon- Shoots 450+ Yards!
EDIT: 23/05/2010 - I've updated two photos of the cannon. I've removed the stock because it was unnecessary and I only put it on there to help with my school assignment. Removing it wont effect performance and sheds weight.
Versatile Antenna Launcher is a cannon I made for a school assignment. I was required to build a cannon that could shoot a pocket nerf with a fishing line attached over a tree. Since it was going to cost me a fair amount of cash I decided to make it over-kill with a 2" piston valve.
I also made a golfball barrel for it as well. This cannon will launch a golfball over 450 yards at only 115psi. At 60psi it will launch a nerf over 120m. This is a very powerful cannon and must be treated with respect as if it was a real firearm.
In this How-To I will teach you how to build one of your own cannons and how everything works so you understand what you are doing. It doesn't have to be exactly the same as mine, you can change it up a bit. Just be creative.
Chamber:About 5' of 2" pressure rated PVC pipe and fittings.
Barrel:3' long 2" barrel or a 5' long golfball barrel (1.5" SDR 21 PVC)
Main Valve:2" Piston valve, 1.5" seat (what the piston seals against)
Pilot Valve (What triggers the cannon):1" modded sprinkler valve
Fill Valve (where you fill the cannon up with air):1/4" brass Quick-Connect
Velocity:Golfball - 200ms (650fps)
Distance:Golfball - 420m+ (450+ yards)
I do not take any responsibility for your actions if you choose to follow this How-To. This is meant only for a learning purpose so you can understand how these work and what it takes to build one. If any thing goes wrong it is your own fault and I cannot be held liable. By reading this How-To you accept to my terms and conditions of this disclaimer. Treat this as a real firearm, it has more then enough power to kill, never point this cannon at a living person or animal even if it isn't loaded or pressurized. Do not destroy public or private property. Never take this cannon off your own property and only fire it when you know what you are shooting at, you have a good backstop and know that there are no people around. Keep it safe.
The cannon can also be seen here at SpudFiles:
Step 1: Getting Started
A few things you should know before starting out...
Always used pressure rated PVC. Never used DWV, which is unpressure rated PVC and can explode at such pressures. DWV may be cheaper or easier to find but it is not worth it. I live in New Zealand and pay 1300% more then you Americans do for pressure rated PVC, so just buy the proper stuff.
I made an article on how to identify pressure rated PVC here:
I'm sure most of you are familiar with 'Sch 40' PVC. The 'Sch' rating is not a pressure rating. It is a thickness rating.
In NZ we use a different system but i'll convert it over for you.
You want to make this cannon with at least Sch 40 NSF-PW pressure rated PVC. Do not take this cannon over 120psi, it can take more but you don't want to push it. If you live in Australia or New Zealand you want to use at least PN12 rated PVC pipe and fittings.
Since I built this cannon with metric fittings, it may differ slightly in America, but it shouldn't be too much off. The only big difference is that in NZ and Australia, 40mm pressure rated PVC fits golfballs. In America you will have to find 1.5" SDR 21 PVC. It may be a bit flimsy so you can sleeve it with 2" Sch 80 PVC. Or you can just buy it online from www.bcarms.com
I will convert all the units to imperial as well as metric. To help everyone out.
Cost and Time
If you live in America this shouldn't cost more then $70-100USD. If you live elsewhere it could cost up to $300 NZD. This cannon took about a weekend to build for me, it will probably take you more. Be preapred to commit to this project.
Step 2: What You Need
Here's a list of what materials and tools I used:
Dremel (Notr Required)
180 (fine) sandpaper
Angle Grinder (Not Required)
Lathe (Not required)
2000mm/78" of 50mm PN12 PVC/2" NSF-PW Sch 40 PVC
1500mm/60" of 40mm PN12 PVC/1.5" SDR 21 PVC
2 x 50mm/2" pressure rated PVC end caps
1 x 50mm/2" pressure rated PVC 90 degree elbow
2 x 50mm/2" pressure rated PVC 45 degree elbow
4 x 50mm/2" pressure rated PVC tee fitting
2 x 50mm/2" pressure rated PVC female threaded socket adapter
1 x 50mm/2" pressure rated PVC male threaded bushing x 25mm/1" female thread
1 x 25mm/20mm male x male threaded brass fitting (1" x 3/4")
1 x 20mm female threaded galvanized 3-way fitting (3/4")
1 x 20mm male threaded brass adapter (3/4")
1 x 20mm female threaded galvanized 90 degree eblow (3/4")
1 x 20mm male threaded galvanized nipple (3/4")
1 x 20mmx25mm female x male threaded bushing (3/4" x 1")
1 x 15mm galvanized male threaded nipple (1/2")
1 x 15mm galvanized female threaded tee (1/2")
2 x 15mm male x 8mm female threaded brass adapter (1/2" x 1/4")
1 x 8mm 0-300psi pressure gauge (1/4")
1 x 15mm male x female threaded galvanized ball valve
1 x 8mm male threaded brass quick-connect (1/4")
1 x 8mm brass nipple (1/4")
1 x 8mm blow gun (1/4")
1 x 25mm irrigation sprinkler valve (1")
2 x 50mm pressure rated PVC male threaded spigot fitting (2")
1 x 50mm pressure rated PVC coupler (2")
1 x 40mm pressure rated PVC coupler (1.5")
1 x pocket nerf
1 x coaxial fishing line mount
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
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.
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.
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:
Step 4: Solvent Welding
I will now teach you how to solvent weld properly to insure a perfect weld with no leaks.
Solvent welding PVC is when you use a cement to weld to pieces of PVC together so they become one. It is essential this is done correctly. Primer is essential also, never leave it out. It helps if the cement and primer are of the same brand also.
What you need:
PVC Cement for pressure applications
PVC Primer for pressure applications
Mthylated spirits (not required)
It is important you do not leave the primer or glue too long on the fitting or pipe so they dry. Try and do this as quick as possible while maintaining composure.
Pour some meths onto the cloth and clean the fitting and pipe that you are gluing together. Once they are clean, wash with water then dry them off.
Apply primer to the fitting that you want to glue, make sure you cover all of the socket with enough primer. Then apply primer to the pipe you want to join it too. I usually apply primer and glue to about 4cm deep (1.5") on the pipe. Make sure you cover all of this area with enough primer.
Apply the cement to the socket of the fitting, covering over the primer, make sure it's even and you have enough on. Do the same to the piece of pipe.
Join the fitting and pipe by pushing them together and twisting 90 degrees. This insures a perfect seal and weld. Hold them together for 45 seconds.
That's it. Make sure you leave it to dry for at least an hour before handling them and wait at least 24 hours before pressurizing them.
Step 5: Putting Some of It Together
EDIT: As of recent, I have removed the back "stock" of the chamber. This is the bit with the 90 degree and two 45 degree elbows at the back. I removed this for a few reasons: to save weight (weighs about 12kg all up IIRC), more efficient (less air required to fill up the chamber to X PSI) and because I like it better without the stock.
If you are building this cannon from the start, it will also save you money as you don't need the extra elbow fittings. You can either have a 90 degree elbow going from the front chamber up to the piston valve Tee fitting or you can still use a tee fitting but block off the port where the "stock" would be with a simple end cap.
Now you just need to put some of the fittings together. I started out with the stock and mid point.
Cut a piece of 2" pipe about 14cm long and solvent weld it to one of the horizontal ports on the 50mm PVC tee. The solvent weld one of the 45 degree 50mm PVC elbows to the other. Make sure the other socket of the 45 degree elbow is pointing up, not down when you glue it. Just look at the pictures. You should end up with a 6cm gap between the tee and the 45 eblow fitting as shown in the picture.
Cut a piece of 2" pipe 20cm long and solvent weld one end to the 45 degree elbow connected to the tee, and then solvent weld the other 45 elbow to the other end of this pipe. Make sure the end port faces horizontal, as in the pictures.
Cut a piece of pipe 7cm long and solvent weld it to the spare port on the 45 elbow. Solvent weld the 90 degree elbow to the other end of this pipe so the elbow faces down in relation to the 45's. The 90 degree and 45 degree fitting should now be flush. (no gap between them)
Cut a piece of 50mm pipe 11cm long and solvent weld it to the 90 degree fitting so it faces down, then solvent weld one of the end caps to the bottom of this pipe. Again just look at the pictures for reference.
Cut a piece of 50mm pipe 800mm long (31"). Solvent weld this to the other horizontal port on the 50mm PVC tee. Look at the pictures for reference.
Step 6: Barrel Support and Breech Loading
The barrel support works by boring out some of the PVC inside two 50mm PVC tee's. This allows the tee's to slide over 50mm PVC pipe.
Grab one tee and stick it in a vice so the horizontal ports are facing up. Find a hole saw that fits snugly inside the ports on tee. Attach the hole saw to a drill and drill out the inside 'lip' in the tee. The lip is a part of the tee which makes the diameter smaller. If you look inside a tee you will see this. This 'lip' stops the 50mm PVC pipe from sliding all the way through. We are going to try and remove it.
Take your time and slowly bore out the 'lip' from inside the tee, if it gets stuck, chuck the drill in reverse This shouldn't take too long, just make sure you are going straight.
Once you've done this to both of the tee's smooth out the inside with a curved file or sand paper. This allows the 50mm pipe to slide more easily.
Solvent weld the two tee's together by their bottom ports with a 7cm long piece of 50mm PVC pipe. Make sure they are perfectly straight and line up, both facing the same way. Now slide the bottom tee over the long 800mm piece of pipe coming from the stock. Try and push the tee far enough down this pipe so there is 4cm of the 800mm pipe sticking out the otherside of the tee. Line the two bored out tee's up with the tee solvent welded to the stock.
For a 50mm PVC barrel, get one of the 50mm male threaded spigot adapters and solvent weld the 50mm PVC coupler to the spigot end (the end without threads).
For the golfball barrel take another 50mm PVC male threaded spigot and cut a piece of golfball barrel about 6cm long. Solvent weld this piece of golfball barrel to the inside of the spigot end on the fitting. You should have about 3cm of golfball barrel sticking out of this fitting. Solvent weld the coupler to that.
I'll come back to the breech loading later.
Step 7: Understanding Pistons
I will now try and teach you the principles behind pistons, how they work and why.
A piston is a cylindrical object that moves inside a piece of pipe. It has a sealing face, which seals against the barrel and a bumper which softens the impact on the cannon fittings when it is fired backwards.
A piston needs to have a tight fit with the pipe it slides in, otherwise it wont work to it's full potential.
In a pneumatic cannon, air is filled in from behind the piston, because the piston is a tight fit the air pushes the piston forward and it seals against the 'seat' which leads to the barrel. Because the seat is sealed, no air can go through it and into the barrel. The air now leaks around the piston and fills up the chamber to a desirec pressure.
The air has more force pushing on the back of the piston, keeping it sealed, then on the front because of the area differential. The air can only act on what area is exposed and since the seat takes up some of this area, there is less force acting on it pushing it back.
Once you remove the air behind the piston by exhausting the pilot volume (area behind piston) with the sprinkler valve (which lets the pilot volume out into the atmosphere) the area acting on the back of the piston pushing it forward, is gone. Now there is only a force acting on the front, pushing the piston back. The piston is sent back at incredible speeds in a split second into the 'bumper' which reduces the impact. Now the seat is open and the air pressure from the chamber flows into it and out into the barrel launching your projectile. This happens in a split second and is usually quite loud.
This is an animation of what happens, I made the same one with 2 different speeds so you can see what happens every frame.
Okay it seems that instructables is speeding up the animations, so to see slower ones just go here instead:
Step 8: Building the Piston
There are two types that i'll show you how to make, a deodorant one and a plywood one. Either one will do.
Find a hole saw with a diameter larger then 53mm but smaller then 58mm. Find some plywood sheet and use the hole saw to but out a few disks. I only needs 3 because the I used thick plywood but you made need more. I'd recommend a piston around 10cm long. So cut as many disks as you need to make that.
Once you've cut all your plywood disks, coat them with waterproof varnish and leave the varnish to soak in. When that's dry get a long bolt and put it through the middle of each disk (drill a hole if needed), tighten the nut at the other end so the disks are tight and can't move. If you have a drill press or lathe you can fix the piston with bolt to it and then sand it down as it spinds around.
If you don't you'll have do it manually with sand paper. I'd recommend making a deodorant can piston instead.
Anyway, sand the plywood piston down so it fits snug inside 50mm PVC pipe and you can push it with your finger. But make sure there is no room around the outside of the piston, the tighter fit the better. The bolt off cut a cricle of neoprene (rubber) the same diameter as the piston. You can usually find neoprene disks at HomkeDepot. This is your sealing face
Grab a metal washer that has a diameter small then 4.3cm but bigger then 3cm. Put your neoprene sealing face on one end of the piston and then the metal washer, put the boll through this and your piston then tighten the nut at the end. Just make sure to apply lube to your piston before using it and your done.
To make a piston for a 2" PVC tee all you need is:
*Neoprene rubber gasket(found in plumbing section, this is your sealing face)
- Suitable bumber
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 9: Construction of the Piston Housing
Once your piston is done you need to make the piston housing.
Get your spare 50mm PVC tee and cut a piece of 50mm PVC pipe 7cm long. Solvent weld it to the socket end of the 50mm female threaded socket adapter and then solvent weld the adapter and pipe to one of the horizontal ports on the tee. If required sand out a small 'lip' inside the adapter to allow the piston to fit through.
Get two 50mm x 40mm PVC bushings and cut 1cm off the end of one of them. Cut a piece of 40mm PVC pipe 15cm long and solvent weld one of the bushings to the end and the other bushing just above the other. Then solvent weld the female socket adapter onto the bushing on the end of the pipe. One bushing should now be inside the adapter, and the other just above it.
Make sure the end of the pipe without the adapter on, is perfectly level. The piston is going to seal against this. It is absolutely necessary it is flat. Solvent weld the bushing that isn't inside the adapter to the opposite end of the tee that the first female adapter is welded too.
See the pictures for help.
The 15cm of 40mm pipe should now be half way inside the tee
Step 10: Finishing Up
Once everything seems to be fine, cut a piece of 50mm PVC about 7cm long and solvent weld it to the tee from the stock and then solvent weld the piston housing tee on top, make sure the tee's line up with each other and are pointing straight.
Now thread on the male 2" threaded adapter with coupler, and sleeve your 2" barrel through the barrel support and you're done. If you want to use the golfball barrel just thread on the other adapter with the 1/5" coupler and sleeve the golfball barrel through the 2" pipe to keep it stable. So you don't have to take the 2" barrel off.
The breech loading is simple, push the barrel in the coupler to lock it, pull it out to load it. Make sure you jam it in tight when you're about to fire something.
Lube up your piston with plumbers lubricant and slide it inside the piston housing, put in your bumper and then thread your 2" x 1" adapter on the back. The point of this is so that if the piston craps out, you can access the piston housing and remove it and put a new one in. But the piston should be fine.
Once that's down, thread your pilot setup on, you may have to do it in pieces so everything fits and doesn't hit the stock. Make sure to use teflon tape as well.
Making the pilot setup is something that you can customize to suit your liking, but you can follow my pictures if you want to do it my way.
Step 11: Painting
Be creative, give it your own paint job or you can follow mine.
Pretty straight forward, you shouldn't need any help here. I'll just show you a few pictures.
Step 12: Variations and Firing the Cannon
You don't have to make the cannon exactly like mine, as long as you keep to the same principles of how piston valves work, you can make your cannon look like anything you want.
Check out www.spudfiles.com for more information and inspiration. It's the worlds largest database and commmunity for spudding.
Firing the cannon:
Make sure every single part as had 24 hours to dry before firing the cannon. Simply hook up your air source (you'll probably need an air compressor, not a 12v compressor), open the ball valve, let the cannon fill up with air, close the ball valve, aim and then to fire just pull on the blow gun handle.
If you have any problems with the cannon, go to www.spudfiles.com and make a topic asking for help.
Or you can email/MSN me, go to spudfiles, find the member 'MrCrowley' and click on the MSN email address