Generally unless you have an o-ring seal on your piston, you don't need equalization holes - enough air can flow around the piston. By adding the holes, you're making your piston less efficient. I tried doing a disk/piston without the equalization hole. When using the air compressor, you could hear...

Ok, the two bad things about this build...... 1.) I have had random trouble with my disk and seal. First thing is that at around 85 psi or less, there isn't enough pressure to unseat the piston. That or I don't have a tight enough seal around the disk/piston and the irrigation housing to create enou...

So here is the build.

If requested, I can move all these images to a thread detailing the build.

For now this will do.

http://imgur.com/a/oNtKk

As long as your solvent welding is sound you should be fine :) It is for sure, have done multiple test fires. With a small spud, I'm exceeding 100 yards easily, but I'm still kicking myself for my foul up in the valve build. I've done lots of PVC plumbing for drains and such, I can't for the life o...

Somehow when I put it all together it came out that way. Not exactly sure why. So I split a peice of rubber fuel line between the barrel and chamber and zip tied it together.

Cannon is done! Test firing at 100 psi yielded a conservative 100 yard shot at a 45* angle. Needles to say my 9 year old son was ecstatic.... :lol: So here is a pic of the final product. As a former landscaper, I had plenty of materials laying around to build it. The PVC pipe was the only thing I di...

Sorry for the delayed response. I started to get the parts together for the cannon, but when I looked at my work bench in the garage, I sighed....Ultimately I spent the better part of 4 days cleaning up my garage. Now I am helping my son with his livestock at the county fair. (mmmmmm, future bacon.....

I am doing Hubb's extended modification of removing the diaphragm and spring and filling the chamber thru the pilot.

I saw it in the pdf file he created and figured I might as well try to achieve optimal air flow without any restrictions.

Ok, so I got all my parts rounded up that I need. Going to do the extra modified irrigation valve. Got lucky and found a couple of schrader valves with NPT threads. I didn't think they were out there and was trying to figure out how to get one installed on a 1/4 inch brass T to put in the cap of the...

I was thinking with a butterfly valve that you could mount it so that the air pressure from the reservoir will force it open. You would need to make a very strong trigger to hold it closed. But then you could run into your trigger binding and not wanting to release. The release on the trigger will b...

Right now I'm back and forth on either building a piston valve or just going with the modified sprinkler valve. Honestly though, I take projects like this and start to over think it. Need to just do the KISS method on the this first build. Simple modified irrigation valve will fit the bill, thought ...

What is the flow coefficient for a modified sprinkler valve.

Think I'm going to go that route as it seems to the middle of the road between a ball valve and piston operated.

This is awesome! I'm looking to build my own cannon, but probably half the size and range of what you are using. I've got the calculator tool and think my design should work good, but I wanted to ask... 1.) What's your barrel length from the valve to the muzzle? 2.) What is the length of your pressu...

Thanks for the link to the calculator! That's a huge help in at least getting part way to where I need to be. I had done the reading on the equations to do the math yourself, but like you said there is going to be many limiting factors. At least with the calculator, I can play around with different ...

Hey guys, newbie here..... Long story short, I'm looking to design a bait cannon. I need some input on where to start in terms of size. I'm looking to build one that will be compressed air, using a spud as the wadding, and needs to be easily portable. In a nutshell, I go cat fishing and bank fish. N...