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

[glass_05]

Here is just a teaser pic. Once the gun is tested tomorrow I will get some damage pics and a lot more pictures of the gun and some specs of it.

Be watching the showcase for me!

[Technician1002]

WOW. I like it. I'll wait for the showcase to find out what you are using for a bumper and piston. That should pack a punch.

:wav:

[jackssmirkingrevenge]

Nice, whoever's napping in the background looks like he won't be resting for long

[frozebyte]

Doesn't look like hes napping. Hes smiling in his sleep, scary... Hes probably just smiling til hes eyes look closed (Chinese proverb: 笑得见牙不见眼)
I may be wrong but is that messy line thing near the tee a decal or something similar?

Good luck!

[jackssmirkingrevenge]

I may be wrong but is that messy line thing near the tee a decal or something similar?

Looks like spilt primer to me

[frozebyte]

I see, maybe he thought it looked nice so he didnt wipe it off?

[Technician1002]

I see, maybe he thought it looked nice so he didnt wipe it off?

Maybe it happened on the underside when it was being assembled and it wasn't noticed right away.

[inonickname]

Once you've spilt primer it's too late

Looks excellent.

[mobile chernobyl]

m.e.k. takes care of "spilt" primer! get it at the Depot. just make sure you wipe it off right away or else it will just dry and you will have just spread the purpleness around.

[glass_05]

yeah. that is primer. its not hurting anybody there

as for the test firing tonight... the piston seals wonderfully, but we couldnt get it to fire. we kept messing with the pitson and bumper and did get a couple of shots up, but they were VERY delayed and the power was horrible.

any ideas what the problem is?

[THUNDERLORD]

...any ideas what the problem is?

It's too late for me to be an @ss.
I got to work early.
....eat some steaks and p*ssy and figure it out later(?)
Beverage is not essential...

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

Anyhow hope you fix your cannon.
it will be simple.
I like your style. 8)

[SpudUke5]

Decrease pilot volume and use a valve that opens quicker to release the pilot volume.

The cannon reminds me of my cannon, which still need a support system and a barrel support, man in lazy.

[glass_05]

I will try messing with the pilot volume and piston some more, as of right now I have it very small by the time I get the bumper in there.

And to trigger it I have a 1inch modded rainbird

[Technician1002]

yeah. that is primer. its not hurting anybody there

as for the test firing tonight... the piston seals wonderfully, but we couldnt get it to fire. we kept messing with the pitson and bumper and did get a couple of shots up, but they were VERY delayed and the power was horrible.

any ideas what the problem is?

I have edited this wiki page to cover some of the math and theory that makes piston valves work and it includes some details that make some tempermental.

http://www.spudfiles.com/spud_wiki/inde ... ston_valve
See the Small Ratio or QEV section for common problems with pistons and their causes.

To troubleshoot the valve, some of the parameters will need to be known.

These are;
1 Piston outside diameter to the valve seat seal diameter.

This is used to calculate the area ratio of the valve and identify the balance pressure needed to open the valve.

2 The pilot volume

3 The pilot EQ port size

These 2 item are used to find the rate the chamber bleeds into the pilot and if the valve lifts, the rate the pilot pressure jumps as the piston reduces the volume in the pilot.

4 The piston friction. A stuck piston doesn't work well. How is it sealed and how well does it move.

5 The pilot valve parameters. Can the pilot valve drop the pilot low enough to open the main valve?

6 Position of the piston in relation to the air inlet. When the piston pops, the chamber air needs to hit the face of the piston and valve seat area without the piston still blocking the flow.

7 Is there a spring? High spring tension can exceed the opening force of some close ratio piston valves and prevent opening. Same if the bumper is acting as a spring.

If you have questions, PM me. I'll be on the road for a couple days with a major league baseball game and an Amature Radio Operator gathering, so don't worry if an answer is slow getting back.

[Gippeto]

any ideas what the problem is?

I suspect that most of the chamber air comes out through the pilot valve, and then it "pops" ??

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.

To check and see, give the piston a wrap or two of tape, grease it up, and try it again.

If it seems like the world might be coming to an end, you've found the problem.

If not, post in detail what DOES happen.