My future Piston cannon needs you

[Marffy]

I'm gonna make a large piston cannon. i hope to have a 4" T with 3" porting. i have done lots of research about piston cannons but i still need a lot more information. i do not plan on wasting $100 on a piston cannon that leaks. i would like to know what the best seal material for the seal on the piston. should i have a piston with o-rings on it or just a simple bolt and wooden piston? should i glue or bolt the gasket on? What pilot valve should i use? I was thinking of a bigger ball valve. would a modded sprinkler valve be good enough? I'm no expert at pistons i just need the information that was left out. I would like to use the materials that would give me the absolute best performance. I just want a cannon that doesn't leak and can punch a hole through a house. I plan on using some washer slugs for ammo (bunch of washers with a bolt through them.). could anyone predict the performance of this cannon? could it go through three cinder-blocks maybe? or go through a refridgerator door? I also have one other question. If i used a .5" barrel on a 4" piston and used marbels as ammo would it have a lot of power? or would it have the same power as a simple sprinkler valve cannon? i hope to have a great cannon but i need your help! thanks in advance.

[Crna Legija]

A 1 inch modded sprinkler valve would be good enough
if you use pvc the best seal is pvc glue and primer put it on push the fitting in and turn 90*
if you want the best performance out of the cannon than and o-ring will be best but it will go through two cinder-blocks probly the 3rd

as for a power prediction model it in ggdt

smaller barrel on it will have more power than sprinkler valve but but not massive increase

[MrCrowley]

what the best seal material for the seal on the piston

Neoprene gaskets/sheets from your hardware store will work fine. I can't find the sheets of rubber here, so I just use gaskets, circular neoprene disks with a hole in the middle, like a donut. As long as the hole in the middle is smaller than your seat/sealing surface/barrel, it doesn't matter.

should i have a piston with o-rings on it or just a simple bolt and wooden piston?

An o-ring piston will be better. It means you can have a larger pilot volume and a smaller pilot valve but still get good performance. Of course, still try to keep the pilot volume small and pilot valve big. O-rings will make your piston open faster too.

should i glue or bolt the gasket on?

Epoxy will probably work, but I'd bolt it. It could be ripped off otherwise. If you bolt it, make sure to epoxy the bolt on the sealing face if you think it is possible for air to leak through the piston and out the bolt on the sealing face. Happened to me and many other members.

What pilot valve should i use?

Modden 1" sprinkler will be best. A 2" ball valve is probably better, but the increase in performance is probably minimal, especially if your piston is o-ringed and a modded sprinkler valve gives you a nice trigger.

and can punch a hole through a house

Why would you want that? Please refrain from saying such things as it implies you have bad motives for this cannon.

could anyone predict the performance of this cannon?

GGDT. If GGDT doesn't work, i'm sure someone will run a scenario for you eventually but if you don't know how to use it, learn. All the info is on the site.

could it go through three cinder-blocks maybe? or go through a refridgerator door?

How long is a piece of string? With the right projectiles, yes.

If i used a .5" barrel on a 4" piston and used marbels as ammo would it have a lot of power?

I have no idea why you would even bother. It wouldn't be good for the cannon I don't think. A cannon with a 3/4" QEV will probably get similar performance as this cannon would. You need to build another cannon if you want to shoot .5" projectile from a .5" barrel. If you want to shoot a .5" projectile, do it from a 1.5" or 2" barrel, perhaps even 3", you'll get far, far better performance.

[Gun Freak]

A 0.5" barrel is awfully small for a 4" piston!
My piston cannon works fine with no O-rings around the piston but I do have a neoprene washer for a sealing face. Definitely use one of those...

Good Luck with your cannon!

[Marffy]

and can punch a hole through a house

Why would you want that? Please refrain from saying such things as it implies you have bad motives for this cannon.

I just wanna know how powerful it could be. It could shoot exteremly far and hit something. i dont plan on shooting my neighbors house or anything.

[MrCrowley]

It could shoot exteremly far and hit something

If you ever shoot your cannon and it doesn't hit anything, I would be very worried.

Don't expect great accuracy though, you could hit a fridge at 100' fairly easily though.