Here is a pneumatic gun that i built. I recently posted a similar version that you may have seen but i decided to change it up and make the version you see here because many people could not obtain materials used in the previous version. I tried my best to make this pneumatic gun out of the most easily acquirable materials that i could think of such as syringes instead of metal pistons. I made the tutorial as detailed as possible so i hope you enjoy it, but as pictures sometimes miss intermediate steps that videos do not, it may be advantageous for you to watch the video attached as well. And as always for more projects like this you can visit my website, joshbuilds.com, or check out my youtube channel or subscribe to me on instructables. Enjoy !!
Step 1: Materials
For this build you will need:
- a large 60ml syringe
- a small 3ml syringe
- tube to connect the syringes
- some wood
- a drill
- a brass tube
- a projectile that fits inside the brass tube to create an airtight or near airtight seal
*note a brass tube is not the only thing that will work as the barrel of the gun. any cylinder near the approximate size of the barrel i used and a projectile that makes a near airtight seal with the tube will work too. for example a straw and a small plug from a potato could work or a spitball
Step 2: Preparing the Small Syringe Cyinder
Start by drilling small hole in the side of the small syringe. The purpose of this will be explained later but be sure to remove all the burrs from the inside so the movement of the piston will be impeded as little as possible
Step 3: Preparing the Small Syringe's Piston
remove the rubber front from the small piston and apply supper glue to the inside of the piece of rubber. Then re-attach it and leave it to dry. This will ensure the rubber piece doesn't fall off of the plastic shaft it is attached to if it is to get caught on the edge of the hole of the cylinder.
Step 4: Creating the Firing Mechanism
At this point it is important you understand how the gun will function. Looking at the 4 picture you can get an idea of it. what will happen is when the user pulls the large piston inwards it will push the air into the small piston. Because of the ration of the big piston pushing air into a smaller piston the smaller piston will resist movement and pressure will build up in the tube and the large piston. Once the pressure reaches a certain point the small piston will move backwards. Once the small piston passes the hole that was drilled in the small cylinder, the pressure will release through the small hole and into the tube leading to the barrel of the gun. Now the reason we drill into a piece of wood is to ensure strong connections that will not break with bending or pressure.
To start off we drill a hole through a piece of wood. The hole should be the approximate size of small syringe and should go all the way through the piece of wood.
Next drill a hole on an angle through the wood to intersect the other hole. this hole should be the approximate size of the tube and the hole should lead to where the hole in the syringe would be .
Next glue a tube in the hole drilled on the angle. Make sure the seal is airtight. then push the small syringe into the hole and attach another tube to the front end of the small syringe. The tube coming in on an angle when blown into should push air through the side hole of the small syringe and out one of the ends of the small syringe. Make anywhere there is a hole in the block of wood is sealed airtight by adding hot glue.
Step 5: Making the Structure of the Gun
For the structure of the gun we will simply use rolls of paper. For one you will need to roll it as small as possible. The next one should be larger and rolled around of the one you previously made. once the larger one is made you can push the smaller one out from inside
Step 6: Building the Structure of the Gun
In these next steps keep in mind that the only purpose of the paper is keep a rigid structure. Start by cutting the small piece of paper pushing it over the piece of tube that will attach to the large syringe. go ahead and attach the end of the large syringe to the tube that connects to the end of the small syringe. Then cover this with the roll of paper. Glue the roll of paper to the large syringe and to the block of wood so it keeps a rigid structure.
Next attach the rest of the small tube to the block of wood and the large syringe. again add glue to both ends so the structure remains rigid
Step 7: Attaching the Barrel of the Gun
Add the large roll of paper on top of the large syringe then on top of the large roll of paper glue the barrel of the gun. Attach the tube coming out of the block of wood on the angle to the back of the gun's barrel. You can also make the projectile. For this i just used around steel round non hollow cylinder that fit will inside of the barrel. But as i said in the beginning you can use other things like a straw for the barrel and a potato plug or spitball as the projectile
Step 8: Finishing Touches
To finish it off all i did was trace out the gun and add trace out a shape that looks like a handle. Once traced out i cut two pieces out of foam board and glued one on each side. This is strictly for looks and has no functionality.
Step 9: How to Load and Fire
To Fire the gun start by pulling the small piston backwards so it doesn't block the flow of air. Then pull the large piston all the way out. Push the small piston back in and then load the barrel with the projectile. When you are ready to fire hold the large syringe with one hand and pull the piston in with the other hand. Once the pressure builds up enough the gun will fire. It does require alot of force to generate enough pressure to make it fire so if it is not working make sure you are squeezing it as hard as you can. If you still cant get it to work try letting someone who might be stronger firing it. Or to test it you can pull the large piston in then when the pressure has built up have a friend pull the small piston outwards. This will fire but not with as much power but is a good way to test if you are having a hard time creating enough pressure to make it fire
Note: if you cannot generate enough pressure to make the gun fire you can replace the small piston with a medium sized 10 ml piston. This will make it fire at a lower pressure however it wont be as powerful