Barrel sealing piston with "floating seal"

[alkalineall]

I am currently working on (hopefully) my last project in my pvc addiction. Its a dual 6" chambered barrel sealing piston cannon with a 3" barrel. The setup is thus: The two 6" chambrs feed into two 4"elbows and then into a cross. The piston is going to be housed in the rear section of the cross. Now here is my question, because I want a high rate of flow, I'm using a 3" output and therefore piston seal. because 3" and 4" pipe allow very little room between each other when setup coaxially, I'm positioning the sealing face of the 3" pipe halfway in the cross fitting. I'm planning to have my piston in the rear like I said and with a rod extending into the middle of the cross with the barrel sealing face on it . This way flow is not constricted. I believe it should work just fine, and the only difference between this and a design I have used succesfully many times is the rod with the barrel seal extending forward from my actual piston. Usually my barrel seal is on my piston like most other setups that I've seen. What does everybody think? I would just go ahead and build but the supplies for this project weren't cheap. At all. 6" fittings are spendy Thanks a lot.

[zeigs spud]

well i get it lol...i think..when i post my ideas i usualy just make a pic on ms paint and host it, then explain wht the pic can't (just would b kinda easyer to me) anywho yea i don't c why it wouldn't work but i wouldn't wana do it cuz of 1 the size, i just wouldn't feel comfterbal making a piston cannon that large cuz u never c them that big, but hey shoot for the stars lol...or shoot patatoes lol...srry bad joke..well and 2 seems to be alota bends with the elbows. How about you make eighther 1 really large chamber or a really long one. But yea it should work.

[alkalineall]

Yeah a pic is worth a thousand words. All of my cannons thus far except 1 use a 4" piston valve like this (almost) and work really well. The only thing I'm not sure about is mounting the sealing face on a threaded rod and moving it forward. Oh and the bends are all 4" so I don't think that air flow should be restricted by them. And the dual 6" chambers I just thought would be overkill of the fun variety. Thanks for your feedback. I'll post my finished results and pics when I'm done.

[zeigs spud]

well, try to work out the kinks! lookin forward to seeing cannon.

[alkalineall]

Huh , I must've written about a pretty uninteresting topic judging from the lack of comment(with the exception of Zeigs Spud, thanks)

[boilingleadbath]

Sounds kindof like a barrel-sealing supah.
Go for it; it'll work. Be sure to make sure your piston can't turn sidways... it'll need at least two contact points reward of the sealing face.

[alkalineall]

I don't completely understand what you mean by contact points, could you elaborate a little bit? The piston itself will be completely housed in the rear section of the cross fitting and the barrel sealing gasket will be on the end of a threaded rod attached to the piston. I'm doing it like this so that the barrel port is in the middle of the cross with full air flow available. Thanks for your comments.

[boilingleadbath]

The line was intended to tell you "don't use a single washer as the [actual] piston", or something along those lines.

Reason being that it'll turn sideways and F stuff up.

Understandable, or do I need to go and draw a picture?

[alkalineall]

No I get it. You mean have 2 contact points with the piston walls and enough distance between them to discourage jamming in the bore I do believe right? So you think that the part about the sealing face on the rod is okay huh? I've just never seen it done that way.