SpudFiles

i don't understand how the construction of a air cannon with a piston to make it shoot semi automatically. can some one please help.

If you understand how a piston valve works, then all you'd need to do is make a trigger that closes the fill valve and opens the pilot valve in one motion.

This could be done with something as simple as 2 blowguns and a spring/cable.

well there are several ways of doing it... first of all you can use a NO (normally open) 3 way valve.. - the valve that would let air to the gun and then block the incoming air while venting the pilot side... spool valves are one example of such valves.. but a slide valve is used more commonly

the only thing is i dont know how it works

Basically when you fill the chamber the air pressure forces the piston against the barrel sealing it. Right? Ya with me? Using a pilot behind the piston the air rushes backwards opening the barrel and the air goes out the barrel. Anyone got a diagram on this?

There are plenty of topics with diagrams on Spudfiles about how a piston valve works. You could try searching for them.

ok thank you umm if any one has any diagrams they would like to show me that would be greatly appreciated

animated pistons
http://www.spudfiles.com/forums/piston- ... t8157.html

thank you so much i now understand