Intro: Inner Tube Air Gun
I decided that I wanted to make something which used air pressure to fire a projectile but using literally just items found around the home.
I like spud gun projects which use pvc and such like but the truth is most people don't have pvc and valves laying around their home.
This project uses an inner tube as found on a push cycle. I have literally tens of these around which have suffered punctures and because the cost (I pay less than 50pence each) it doesn't make sense to try repair them.
This is my first project using a inner tube and I'm sure it could be modified to produce much better results and be easier to use.
The end result is a air pressure powered gun which can launch projectiles. You could modify the projectile into a rocket or something cool like that if you don't like guns :)
So all you need is:
An inner tube from a push cycle
A standard pump used for inflating your push cycle tires
A projectile such as an old 35mm film canister
Hot glue gun OR elastic band
For your safety I must insist that you wear some kind of armor when carrying out this instructable. In the video I was wearing a kevlar skin color shirt inc ase the rubber inner tube was to explode and the sharp shards of thin rubber sliced through my torso. Also I must insist you wear some kind of eye protection again in case those shards get you. In the video I'm wearing low profile security specs which are hard to make out but please ensure you wear them :)
Step 1: Prepare Inner Tube
The first step is to cut your inner tube. I cut about 10 inches either side of the valve but you can pretty much experiment as you want with this.
Next I used a hot glue gun to glue shut one end of the inner tube. I allowed the glue to harden and then bent the end over about half an inch and glued that down, ensuring an air tight(near enough!) seal. Alternatively you can simply use an elastic band to seal the end tight by wrapping it around several times tightly. I tested both methods and experienced no difference so for ease of use you may want to just use an elastic band!
For your safety I must insist that you wear some fire proof gloves when handling a glue gun, they get mildly hot and there's a possibility the gun or melted glue could scold you. Also please wear eye protection when handling elastic bands.
Step 2: Choose and Insert Projectile
Next you much find a projectile which is slightly larger than the inner tube. I found that little plastic 'eggs' that you get in 'kinder egg' sweets is perfect, otherwise you can use film canisters and similar.
In a later project I want to modify this to be a little more advanced and have a barrel where other projectiles can be used.
To insert the projectile all I did was pull the rubber inner tube over the canister about 1cm so it was tight.
Step 3: Fire!
So okay, I admit the firing method is a little unusual, maybe even awkward but I personally had no problems with it. You should attach a pump, it can be a hand pump or foot pump. I chose a foot pump.
Next hold the 'gun' so that it has a slight kink in the tube about an inch or two before the projectile. This is so that pressure builds up in the other half of the inner tube.
When you want to fire you simply aim the projectile and let go of the kink. I only used a short piece of tube and hardly inflated it but the force was very very strong so take care. I wouldn't advise aiming this at anyone.
Depending on the quality of your tube you may find that after about 20 firings it begins to split at its seams. I have blown up inner tubes before and it took a hell of a lot of pumping and other than a loud bang I wouldn't consider it dangerous but take care anyway.
The additional pictures in this step are just modifications I tried such as removing the valve and hot gluing it into another piece of tube once my current one became damaged and a picture of a gun with a second air reservoir for increased power.
For your safety I must insist that you wear some kind of armour when carrying out this instructable. In the video I was wearing a kevlar skin color shirt incase the rubber inner tube was to explode and the sharp shards of thin rubber sliced through my torso. Also I must insist you wear some kind of eye protection again incase those shards get you. In the video I'm wearing low profile security specs which are hard to make out but please ensure you wear them :)