- Forums - Links - Home - New Stuff -

GB Cannon

Ebay is to blame for this one!  I saw some Goyen quick exhaust valves on Ebay.  They were going at a ridiculously low price, only $9.99 for 3 valves!  After shipping they were only $15 for 3!  I got the valves, which I thought were only 1/4-1/2" valves.  It turns out they were much bigger!  

Armed with 3 new valves and a dream I set out to fulfill my destiny.  (LOL, just kidding)  I found that the valves had a flange on the inlet side and an unknown size on the outlet.  I researched various pipe sizes with no luck.  I ended up taking a piece of 2" sch80 with 1.5" sdr 21 sleeved inside of it, boring the sdr 21 out slightly, and securing it to the valve with JB Weld.  I fabricated a flange to fit onto the valve's flange out of a 1.5" sch80 PVC flange.  The rubber gasket between the flanges was freakishly found on the ground outside of a metal scrap yard.  I couldn't have asked for a more perfect fit on the gasket!

The valve is triggered by a Gregory high flow blowgun.  The gun is filled through a male quick connect fitting.  If you have ever played with quick connect fittings, you know that the males are not air tight.  If I were to release the hose, the gun would trigger.  To avoid this, I followed the quick connect fitting with a 1/4" inline check valve.  These can be found at   

The chamber is made of 4" clear pvc.  I had planned on using it for a combustion, but couldn't resist the coolness of a clear pneumatic.  When fired, the chamber becomes filled with vapor from depressurization.

Overall, I am amazed with the power of this gun.  The Goyen valves are much more powerful than a sprinkler valve of the same size.  Its hard to explain, but a sprinkler valve, even a pneumatic modded one shoots kind of "squishy."  Sort of a whoosh-bang sound.  The Goyens dump very crisply, with a sharp retort.  They remind me more of a piston valve than a diaphragm valve.  

The day after initial testing, my stomach was really sore.  I had rested the gun on my stomach and legs so I could hold the barrel shut with my hands while firing.  The recoil gave me some nice bruises!

gbcannonback.jpg (450106 bytes)      gbcannonvalve.jpg (371207 bytes)

gbcannonside.jpg (377234 bytes)                                                                                  

"Bolt Action" Loading Mechanism

I decided to try a new method of loading with this launcher.  It has a golf ball "bolt action" mechanism.  The mechanism consists of a 2" repair coupling (sliding type).  It is attached to a 2" sch80 barrel, which has 1.5" sdr 21 sleeved inside of it.  When pushed forward, the loading hole is exposed.  You drop a golf ball in, and pull the repair coupling back.  The repair coupling is airtight via o-rings but slides easily.  The golf ball is sandwiched between the short gold screws and the inner barrel.  As you push the barrel/coupler back the golf ball is loaded into the inner barrel.



There is a slight problem on the barrel.  When fired the bolt/ barrel flies forward, letting air escape from the loading hole.  This reminds me of a gas blowback system, which could in some cases be useful.  A semi automatic design would be one of these uses.  I will be fixing the barrel so it will not slide forward when firing.


navigation may be malfunctioning... fix to come soon.