When I was a kid, I used to play with this gun, it is easy to make and very fun to play with.
Sambucus (elder or elderberry) is the type of wood that has a hole through the trunk, this hole is filled with some spongy material which has to be removed for this project, I'll guide you through the whole process of making this gun.
Step 1: Operation principle
The principle is, you have two caps each on one side of the pipe, when you're pressing one cap close to another one you are compressing the air and then that compressed air pushes the second cap out of the pipe.
Step 2: Tools and materials:
-a metal rod
- hemp ( that's what google translate translated, I don't know exact english word for that, I know that this thing is often used for caulking the pipes, but in further steps I'll call it hemp)
Step 3: Find elder and right shape of wood
I put some descriptions in pictures.
So, the task is simple, find the elder and cut the piece of it. The best elder for this is usually about 3-4 years old, then the hole is right diameter.
Step 5: Removing the spongy stuff
Take some long metal rod and try to push it all through the whole wooden part, that way you should remove spongy stuff. That's the way how I was doing it, if you have some other better idea just post below because I'm searching for some better way.
Step 6: Adding wider cap on metal rod
It is smart to do that because that way metal rod can't pass through the hemp cap and it can not damage the pipe.
Step 7: Cleaning the pipe
Make some balls from hemp so they can fit in the hole, soak them in the water and then push'em through the pipe couple of times.
Step 8: Finding the right side
It is not the same if you try to push the hemp cap through one or other side, it is because the wood is conical shape. You know that you find the right side when you are pushing harder and harder through the pipe, it is good because then is seals gaps and stops the air from passing through.