well before we begin i must state a few things...
-PVC can only be used at half or less than half the pressure rating stamped on the pipe when pressurized gases are used in the pipe
-i would suggest never pressurizing this cannon above 150 psi, remember its only plastic
-never store any type of PVC pneumatic with pressure still in it
-always allow a full 24hours for PVC glue to dry before pressurizing
-when building pneumatics always use metal or PVC pipe (never ABS)
-PVC is shock sensitive meaning if its dropped on a hard its very likely it will be damaged and it would be very dangerous to pressurize after damaged
-PVC becomes very brittle below 32 degrees (Fahrenheit) and is very likely to explode if pressured in such conditions
-when building pneumatics pressure rated pipe should always be used (none of that cell core or DWV crap)
-the most important part of any pneumatic are the PVC welds AND I HIGHLY SUGGEST YOU READ THIS TUTORIAL before you even think about starting this.
-when you are dealing with high velocity projectiles always remember you safety glasses
-always be sure of your back stop when shooting any form of rifle, pistol, gun, bow.... anything that can fire some vague form of projectile
-and use common sense!
-do not use un-regulated HPA or CO2 in a PVC cannon ever they are stored at to high of pressures to be safe in PVC, but if you have a properly regulated setup they can be used ( if you lower the pressure to about 100psi)
Now onto the good part...
this is my entry for the launch it challenge, it is a 25MM Pneumatic Cannon. it has 2.5 foot long one inch diameter barrel with a custom bolt action mechinism, of course we have the 3-9X40 sniper scope, and a 1" modified sprinkler valve as the primary firing valve.
invalid movie: http://youtube.com
remember always wear safety goggles, you never know where or when something will ricochet especially when its traveling at 300+FPS
Fun Fact: PVC shards can't be picked up by X-Rays (this is a safety tip! don't rush or you'll get a PVC shard in you and you probably wont get it out. im not saying you should sneak one of these into your luggage and go threw airport security. it would be way to big any way)
better video coming soon
If you like this instructable please register and vote for it in the launch it challenge (by click the plus icon next to the title)
power source------------------compressed air
power source pressure-----100psi
chamber volume--------------45 ci (approx.)
barrel volume------------------25 ci (approx.)
c/b ratio--------------------------1.8 to 1(approx.)
firing valve----------------------pneumatically actuated sprinkler valve (a "modded sprinkler" valve)
pilot valve-----------------------blow gun valve
fill valve--------------------------female quick disconnect
fire rate--------------------------single shot, bolt action
caliber---------------------------25MM ( one inch)
projectile velocity-------------unknown (coming soon)
effective range----------------unknown (coming soon)
maximum range-------------unknown (coming soon)
optics---------------------------3-9X40MM rifle scope
primary material used------PVC pipe
I WOULD SUGGEST YOU DO SOME RESEARCH BEFORE UNDER TAKING THIS PROJECT, LOOK INTO THE DIFFERENT TYPES OF PIPE AND THERE RATINGS, HOW TO SOLVENT WELD PVC (THIS IS A MUST), HOW TO PROPERLY DRILL AND THREAD HOLES FOR FITTINGS, THE TYPE OF CONDITIONS PVC CAN BE USED AND STORED IN. THE MAJORITY OF THIS INFORMATION IS CONTAINED WITHIN THIS INSTRUCTABLE BUT IT IS BECOMING CLEAR THAT MANY OF YOU ARE NOT READING ALL OF IT. I HAVE ONE FINAL SUGGESTION BUILT A BASIC PNEUMATIC OR COMBUSTION FIRST IF A BASIC CANNON FAILS IT WILL BE LESS DANGEROUS
PS - DON'T ATTEMPT THIS AT ALL IF YOU HAVE NO COMMON SENSE OR A LOW IQ
Step 1: The Parts...
( 1x ) 2" PVC cap
( 1x ) 2" PVC coupling
( 1x ) 2" to 1" PVC bushing
( 2x ) 1.5" PVC couplings
( 2x ) 1.5" to 1" PVC bushings
( 1x ) 1" PVC tee
( 2x ) 1" PVC 90 degree elbows
( 2x ) 1" PVC male threaded adapters
( 1x ) 1" to .75" bushing
( 1x ) .75" PVC cap
( 1x ) .75" PVC tee
( 3x ) .75" PVC 45 degree elbows
( 2x ) .75" PVC 90 degree elbows
( 1x ) female quick disconnect 1/4"
( 2x ) 3/8" by 1/4" compression fittings
( 1x ) blowgun valve
( 1x ) 1" sprinkler vlave
a few inches of 1/4" ID flexible tubbing
assorted bits of 2", 1.5", 1", and .75" pipe
a band saw
a drill (preferably a drill press)
PVC primer (make sure its primer and not cleaner or it could end badly)
Step 2: The Chamber...
The chamber in a pneumatic cannon is a buffer zone between the valve and the bike pump/ compressor. It allows a large amount of air to be stored and exhausted very quickly when fired.
this is my chamber, it is a 12 inch long piece of 2" PVC pipe with a 2" cap on one side and a 2" coupling on the other, attached to the 2" coupling is a 2" to 1" reducing bushing. After the chamber was glued i let it sit for an hour (so the glue could partially cure) then i drilled a 1/2" hole in the side of the 2" cap so i could thread in the brass quick disconnect. do not use any Teflon tape on this fitting, if it starts leaking put some epoxy putty or JB weld on the section where the threads meet the chamber.
Step 3: Gun Body...
first cut a piece of PVC double the length of a 1" socket and glue it into one of the 1" PVC elbows. then insert a a long piece of 1" pipe into the 1" elbow and the 1" tee( but don't glue it) this will help you get the joint between the 1" elbow and 1" tee perfectly straight. now glue the short piece of pipe sticking out of the the 1" elbow into the base of the 1" tee, use the long pieces of pipe to make the joint as straight as possible or the barrel will be off to the left or right of the gun. next is a rather odd step listen closely, i want you to glue the outside of the 3/4" end cap into the the back of the 1" tee. there are two things you want to remember here not all end caps will work do a dry test before you glue it and this is the part where the stock is connected to the body so make sure you insert the cap the right way (so the socket part is facing outwards making it possible to insert a piece of 3/4" pipe). next cut 7" piece of 1" pipe and glue it into the remaining socket of the 1" elbow.now cut a short piece of pipe and connect one of the male adapters to the remaining socket of the 1" Tee. the last piece your going to need a dremel for you need to modify one of the 1" 90 degree elbows to it can slid along a 1" piece of pipe relatively easy. sadly there is no trick to doing this your just going to need to take of a little material at a time until you get it just right. once the elbow has been modified glue the 1" to 3/4" reducing bushing into its unmodified socket then slide it onto the 7" long piece of pipe which is now glued in place. then glue the other side of the 7" long pipe to the chamber. you have now finished the body of the gun.
Step 4: The Stock and The Valve
onto the valve, my valve is an orbit jar top that i have modded. normally it would be triggered by an electronic pulse but this does not allow the valve to open quickly so i modified to to run completely pneumatically , there are many tutorials on how to do this for example here is one here is another. if you cant figure out how to mod the valve i suppose you can buy one from here, i know the guy who runs that place hes not going to scam you and his work is very good quality. anyway to install a sprinkler valve on this particular cannon aply a good amount of Teflon tape to the 1" threaded adapter then remove the top of the valve and screw on the valve itself.then go ahead and put back on the top. do not put on the blowgun as of yet.
side note: be sure to put the sprinkler valve on the right way, becuase it will only work in one direction. there should be an arrow some where on it indication the direction of flow, remember the air is going to be flowing from the chamber to the barrel
Step 5: The Bolt and Barrel Assembly
now we must build the the actual bolt handle; it's one of the simpler pieces. it is a hose clamp with a hole drilled through it and a dowel held in place with a wood screw. it does take a bit a measuring and test fitting to get the hole in the right place, but its worth the time to get it right. after you have screwed the handle onto the clamp insert the barrel into the bushing then put the hose clamp on it loosely. now force the barrel as far back as it can go, you should notice that it can actually go into the other bushing and it is very important that it does. once this is complete, tighten the clamp onto the barrel very tightly.
note : you can make the barrel pretty much however long as you want it. mine was 2 and a half feet of 1" pipe
Step 6: Scope Mount and Other Add-ons
barrel supports are small pieces of wood (in most cases) cut to the profile of the pipe, they add stability to the launcher when fired and take a great deal of stress off the joints. i would highly recommend you make some for you own safety. i traced the outline of the pipes onto card board then transfered that to a piece of pine that was cut by my band saw to make mine.
next up is the scope, my particular scope was made for an airsoft gun (almost identical replicas of real guns ) and it used an RIS mounting system. this meant i needed a RIS rail to put on the body of the rifle. for me RIS rails are very common and easy to find becuase i happen to have about 10 semi working airsoft guns (i got them in trade for a piston valve). if you don't have any buy a crappy gun for $10-$20 off hobbytron.com or a similar supplier. the RIS rail was attached to the gun using 2 hose clamps it took a bit off adjusting but eventually i could shoot the gun pretty accurately.
additional items to consider...
a "noise reducing barrel extension" *cough* silencer *cough* but if your caught with that your screwed and that is exactly why im not telling you how to make one.
a bi-pod, i have one from an AK support type gun but cant find a good way to mount it
laser sight, well it would only be useful at night
Step 7: Trigger assemlby
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