I made this piston for my 1/8" coaxial gun with 12(10)" of 1/2" chamber, 1/8" 30" rod for barrel.
I didn't take a picture of the finished product but after this was taken the head of the bolt was dipped in epoxy resin for barrel sealing surface (about 1/10" thick, if that), the rubber part is bumper and pilot sealing surface (which was extended so no stud is exposed) and I added an extra o-ring... total piston travel: 1/4"~
10 minute pressure test @ 1000psi and 5 1000psi test shots, gun made for 400-500PSI.
Posted: Thu Sep 01, 2011 7:08 pm
by mattyzip77
looks good, me likey!!!!
300 posts! 8) 8) 8)
Posted: Thu Sep 01, 2011 7:28 pm
by Gun Freak
Looks really heavy for a 1/2" piston.
Posted: Fri Sep 02, 2011 12:49 am
by sco77
Gun Freak wrote:Looks really heavy for a 1/2" piston.
It's not as heavy as it looks, but even so it's for high pressure, has a good seal and not a very big travel... It performs pretty nice and has a nice bang to it for being such a low caliber barrel.
Posted: Fri Sep 02, 2011 1:02 am
by Technician1002
It does not have to move far to open. The barrel is 1/8th inch. Valve is open at less than 1/16th inch travel.
Posted: Fri Sep 02, 2011 1:12 am
by jackssmirkingrevenge
Looks a little over-engineered, for this 1/8" coaxial I got on fine at 850 psi with simply a rubber cylinder cut from 1/4" neoprene sheet.
Posted: Fri Sep 02, 2011 2:49 pm
by Brian the brain
Can't get much better than this!
Love the simplicity.
I almost forgot I used a solid rubber disc on " the pirate" (pretty long ago!!) wich had a 15mm barrel port and I had no problem with it at 26 bar.
So 1/8" should work fine..
Posted: Sat Sep 03, 2011 12:10 am
by sco77
Does the valve sound like it's performing like it should? This is around 400psi about 10 feet from the camera..
[youtube][/youtube]
Posted: Sat Sep 03, 2011 12:29 am
by jackssmirkingrevenge
Sadly noise, especially recorded noise, is a poor indicator of shot power. What projectile are you shooting? A 1/8" ball bearing should go through both sides of a soup tin easily at 400 psi.
Posted: Sat Sep 03, 2011 12:40 am
by sco77
jackssmirkingrevenge wrote:Sadly noise, especially recorded noise, is a poor indicator of shot power. What projectile are you shooting? A 1/8" ball bearing should go through both sides of a soup tin easily at 400 psi.
That shot was just an indoor shot with rice (turns to powder after 1 layer of cardboard)..
I shot small screws and metal caps at 500PSI and went through some pretty thick metal (about 2x thickness of canned goods), and smashed or bent projectile. Unfortunately I have no way of measuring FPS so I don't know if it's performing as quickly as it should.
Posted: Sat Sep 03, 2011 12:42 am
by jackssmirkingrevenge
sco77 wrote:I shot small screws and metal caps at 500PSI and went through some pretty thick metal (about 2x thickness of canned goods), and smashed or bent projectile. Unfortunately I have no way of measuring FPS so I don't know if it's performing as quickly as it should.
That sounds about right for your barrel length and pressure.
