1.5 piston coax

jonnyboy · Sun Feb 15, 2009 6:03 pm

This is my first working piston gun. The chamber is 1.5 inch pvc and the barrel is .75 inch pvc. The gun was designed to shoot primarily empty co2 cartridges.

The ammo stop prevents stuff from falling out.

The can was sitting on the ground with nothing stopping it from moving back.

The whole gun.

Future updates

Sprinkler valve pilot-right now I think I'm losing a lot of performance becuase of the ball valve, there's a small delay in opening time and firing.

Paint job-ugly primer stains

Any criticisms are welcome. I would love to improve on my design!

Happy spudding!

jor2daje · Sun Feb 15, 2009 8:17 pm

Why the two ball vavles?

Velocity · Sun Feb 15, 2009 8:30 pm

jor2daje wrote:Why the two ball vavles?

A large (looks like 3/4") ball valve for piloting, and a smaller (maybe 1/2" or so) ball valve for preventing the cannon from firing when the female QD is disconnected from the male QD on the cannon.

jor2daje · Sun Feb 15, 2009 8:38 pm

Why not pilot and fill with the same valve

dudeman508 · Sun Feb 15, 2009 8:58 pm

Why dosent air come out of the holes you drilled to put your ammo stop wire?
jor2daje- maybe its because the 3/4 in is bigger and dosent have a quick connect attached to it so it will increase flow.

jonnyboy · Sun Feb 15, 2009 9:00 pm

jor2daje wrote:Why not pilot and fill with the same valve

The 1/8 opening is hardly a decent pilot, the 3/4 inch pilot has a hard time piloting this, I need a sprinkler valve.Sigh it's just money!

Thanks for the comments tomorrow I'll see if I can get a sprinkler and some damage pictures against plywood and an old vcr.

EDIT

Why dosent air come out of the holes you drilled to put your ammo stop wire?

It does the piece of copper is epoxied into the barrel so the holes don't matter.

Anybody have a good name for this?

dudeman508 · Sun Feb 15, 2009 9:12 pm

[quote]It does the piece of copper is epoxied into the barrel so the holes don't matter. [quote]

Oh sorry you cant see the epoxy in the pic

Edit: Never mind now i get it

daberno123 · Sun Feb 15, 2009 9:18 pm

Whoa you've got a heck of a lot of pilot volume there. By eliminating the huge cross you can pilot with the same valve you fill with.

Instead of your current set-up have it go: piston valve -> ball valve ->then a tee with your gauge and quick disconnect.

This will decrease your pilot volume hugely. The only downside is that your gauge will not show the psi when your quick disconnect isn't connected to the gun from whatever air source you're using. As long as that doesn't bother you its well worth thinking about in terms of ease of use and performance.

jor2daje · Sun Feb 15, 2009 9:41 pm

Ok thanks i get it now, ive never made a big piston gun, so i didnt know the pilot had to be that big

jon_89 · Mon Feb 16, 2009 1:35 am

What did you use for a piston?

jonnyboy · Mon Feb 16, 2009 8:14 am

daberno123 wrote:Whoa you've got a heck of a lot of pilot volume there. By eliminating the huge cross you can pilot with the same valve you fill with.

Instead of your current set-up have it go: piston valve -> ball valve ->then a tee with your gauge and quick disconnect.

This will decrease your pilot volume hugely. The only downside is that your gauge will not show the psi when your quick disconnect isn't connected to the gun from whatever air source you're using. As long as that doesn't bother you its well worth thinking about in terms of ease of use and performance.

If I understand you correctly that means I would be piloting into the tee area with the other ball valve open?

I should be getting a sprinkler valve today for a pilot, that should help with the large pilot volume.When I'm at the depot I'm going to get shorter nipples to lower the pilot volume further.

What did you use for a piston?

It's a hot glue piston,in a while I can take apart the gun and get a picture for you if you want.

I've been experiencing a pretty large leak from the barrel so I took the barrel off and took off the neoprene disk and sanded the barrel smooth. Is my leak becuase of a bad seal on the barrel or a bad piston face?

POS · Mon Feb 16, 2009 10:19 am

jor2daje wrote:Why not pilot and fill with the same valve

Because the air behind the piston would not get out fast enough when shooting, resulting in high loss of performance.
The part behind the piston should get depressed as fast as possible. Pepressing trough the "loadnozzle" is possible, but will result in great loss of pressure in the chamber, before the gun shoots.

jonnyboy · Mon Feb 16, 2009 10:42 am

Well here's the piston:D

Not what you expected huh?

It got owned

Apparently hot glue can't take a 120 psi rebound .

I might try a epoxy piston it should be much sturdier and withstand my uses.

daberno123 · Mon Feb 16, 2009 10:43 am

jonnyboy wrote:If I understand you correctly that means I would be piloting into the tee area with the other ball valve open?

I should be getting a sprinkler valve today for a pilot, that should help with the large pilot volume.When I'm at the depot I'm going to get shorter nipples to lower the pilot volume further.

True, you would be. A sprinkler valve will be more than enough to pilot with. You'll be surprised how much difference it makes.

EDIT: Looks like you need a new piston.

IIRC a 1" coupling is a perfect fit in 1.5" pipe. Try one of those for a new piston.

jonnyboy · Mon Feb 16, 2009 10:55 am

daberno123 wrote: True, you would be. A sprinkler valve will be more than enough to pilot with. You'll be surprised how much difference it makes.

EDIT: Looks like you need a new piston. IIRC a 1" coupling is a perfect fit in 1.5" pipe. Try one of those for a new piston.

Alright I'm heading out soon so I'll pick up a sprinkler and a coupler.