Teaser pic of my 4inch piston cannon EDIT: cannon is done!

[frozebyte]

Leave the primer on! it looks good, scale up a decal on it The primer stain is too small for that big cannon.

[jackssmirkingrevenge]

Judging by your avatar you like big women.
also in the pic it is easy to spot a wet -dreamer.

The pink unicorn is an atheist symbol

Dollars to doughnuts, you've replicated the most common problem with first time piston valves. ie. The piston is too loose in the housing, and blow by can keep up with the pilot valve flow.

Agreed there, get wrapping

[Technician1002]

Judging by your avatar you like big women.
also in the pic it is easy to spot a wet -dreamer.

The pink unicorn is an atheist symbol

Almost.. Invisible pink unicorn is the symbol. Symbol is shown in link below. Try again. It is the wrong unicorn. The purple and not invisible unicorn is not a match.
http://www.religioustolerance.org/atheist6.htm

Back ontopic of the piston, a large gap by the piston is a common reason for high flow from the chamber into the pilot keeping the pilot pressure above that which is needed to fire it. It is high on the possibilities list, but not the only possibility.

[sgort87]

The likeliest problem is number 3 on Technician's list. You probably have too much backflow through your piston from the chamber during the pilot dumping, keeping the piston locked. Try making the flow around/through the piston smaller by using o-rings, plugging the equalization hole and making a new smaller one, or even better use a check valve to ensure no air comes back.

Also, I highly recommend NOT dry-firing this cannon. Always have something with good mass loaded or you risk some bad piston slamming. I broke my last 3"-porting 4" tee is two big chunks while dry firing out of a 3"x10" chamber... yes, a 100 ci chamber.

[glass_05]

got it to fire today! i messed around with the piston and bumper and found a combination of pilot volume that works. i think my main problem was that the foam piece i was using as a bumper was getting sucked into the outlet and that caused it to release the pilot air very slow. also wrapped some tape around piston and used more lube.

only problem i have now is when i fire the gun, the rubber from the sealing face goes into the barrel. i then have to unscrew the barrel and push the piston back further into the tee and then the rubber is free. will work on solving that next.

and thank god that my back plug is easy to take out, have probably taken it out 15 times in the past day to make tweaks.

[LCTChamp]

To stop the rubber from being sucked in bolt ca washer just smaller than the inside diameter of the barrel onto the piston

[glass_05]

I had the biggest washer I could find and that still wasnt big enough. I now have a 2" endcap with the walls cut off and I am using that as a washer. When I screwed the bolt for my piston I didn't center it exactly, it is a tiny bit off, so it is hard to get something in there just smaller than the barrel ID. I will mess around with some other things and hopefully get something to work. As of right now I dont know if i can get anything bigger.

[sgort87]

Just punch the center of the rubber bumper out and it won't be able to get sucked into the vent.

I had that barrel-sealing rubber problem with my first Mauler prototypes. I corrected it by making custom beveled washers that were barely smaller than the valve's outlet port, and cut the rubber to be just barely larger than the outside of the seat diameter. The beveled edge ensures that it will center itself every time and not jam.

[LCTChamp]

Just punch the center of the rubber bumper out and it won't be able to get sucked into the vent.

I had that barrel-sealing rubber problem with my first Mauler prototypes. I corrected it by making custom beveled washers that were barely smaller than the valve's outlet port, and cut the rubber to be just barely larger than the outside of the seat diameter. The beveled edge ensures that it will center itself every time and not jam.

Good idea. I hadn't thought of that.

[THUNDERLORD]

Is it considered "100 proof" to drink enough 5.5% alcohol???
Maybe if coupled with long periods of no sleep and whacko enough replies(?)
It was cool to know, (for sure) someone more knowledgeable would've answered his question and rapidly too was all.
Glad he didn't take my bad humor the wrong way...

...The pink unicorn is an atheist symbol ...

Still IMO (and fully sober now),
it looks more suitable for a "big women" symbol...I can not explain exactly why, just does...
Clicked the link Tech linked to...my impression, "emptyness"..."no soul"..."nothingness"...No thanks for me.
Debate about that doesn't really belong here although it's entertaining on www.theopia.com. But I will say, In many people's opinion "Data" character on "Star Trek" is the LEAST coolest character (androids usually are except for "The Terminator" of course. (if any of them are "cool"). Something to think about...

@glass_05: Got it working yet?
Looks awesome!
Hope to see a vid sometime. Thanks. 8)

[glass_05]

As for my avatar...
It means nothing that you guys have said. It was my avatar for Halo 3 when I use to play that (I wanted something that would provoke flaming on me). And when I went to look for an avatar for this site, it was the only one that met the size requirements.

as for the gun...
I did drill out a hole in the bumper and that helped ALOT, I think I need a bigger hole on that tho yet. For the sealing face, I am going to try to cut the rubber back a little bit and see if that helps. If not I will try the beveled washer idea, or I will get a plunger and use the thick rubber off of that.

[glass_05]

just did some more work on the gun. i found a bigger washer and i cut the rubber down, however i am still getting the same problem with it going in the barrel. might look into so thicker rubber.
and i still only get one shot and then i need to take the back plug out and reset the everything. i think i know how to fix that, and it has to be the bumper that is causing it.

[sgort87]

It probably isn't the bumper. The pressure left behind the piston pushes it forward at the end of the shot while the remaining air flow from the chamber is pushing the rubber into the barrel.

I've also noticed that when shooting without a heavy-enough projectile, the piston has a higher tendency to push forward, while shooting with a high-mass projectile puts more pressure out the exhaust, keeping it from blowing forward as much.

I know it's annoying, but to get around taking it apart all the time, use a ram rod to reset the piston until you fix the problem.

Try a custom washer made from a 3" cap. I wasn't able to stop the jams until the washer was as wide as the barrel port. Silicone both sides of the seal to help keep the gasket in place and to ensure it won't leak.

[glass_05]

finally got it!
here is my new redesigned piston. used a plunger for the sealing face and a bumper.


of course i have a new problem now...the removable plug is leaking. i think a new o-ring will fix that tho. so i am not too worried.

[sgort87]

ooo... Take that bumper off the piston and silicone it onto the back plug instead. You wanna keep your piston mass down, and that's adding a lot for no reason.

good to see you got it working well though.