I went and bought a decent thickness HDPE smooth cutting board an cut out a few circles with differing diameter hole saws. I just had to use a center bit the same size as my rod. As long as you keep the cutting board very stable while cutting the pieces out of it, and round burrs from the edges with...

It would work as drawn but a slide valve pilot would be easier to put together and much more efficient too as the HPA feed is blocked off during firing. What are you using to block the flow of HPA through the slide valve? Its my understanding that the slide valve is just a pass through which has th...

do you think a spring could be used to cushion the piston AND return it back to its original position on the rod? I understand that whatever the rod is connected to would have to be made of very sturdy materials and properly braced.

Ok... so I have to use a bumper... how about a spring with a rubber bushing? Basically I am looking for a way for the piston to reseat itself without me having to manipulate anything like you have in your videos. Is it possible? Would the construction materials play an important role, ie aluminum vs...

I have researched many threads by Technician about his QDV projects, but on thing I would like to know is can a QDV be used without using a bumper for the piston?

I went out and bought a set of white HDPE cutting boards, a 3" hole saw, a round rubber flap valve for a toilet, some rubber gasket making material, tennis balls, a proper length bolt with nylon locknut, and all purpose cement. Made the 3" barrel sealing piston for my coax cannon, no problem.

Since my standard operating pressures will be in the 50-60 psi range... i should be good. Perhaps a wrapping of duct tape would be in order. However I would still be very worried taking her out in this type of weather... personally winter airsoft sux for me anyways... so its not one of my major conc...

I know you said you tried a coax before and it was too heavy, but honestly... if you want compactness, its gonna have a little weight to it. That being said, how bout something like this then? I based my build off of the M2 Carl Gustav found in Battlefield Bad Company 2. The entire launcher is 3 fee...

I used a slide valve as my pilot valve. I have a 3"x2" pilot being released by a 3/4" slide valve. I had to use a shite load of sealant on the threads to get it to seal... but it has never failed me yet.

could the pressure be leaking through your piston? i had this problem with my first piston design... a little silicone in the bolt passage between the bolt/washer, washer/seal, and seal/piston fixed it.

since I am limited to 12g cylinders, i was thinking of a dual 12g adapter, a low pressure regulator, pressure gauge, and either a simple push button valve or electric solenoid to fill the chamber. The push button would be cheaper, but i have room for a switch battery and wiring for a solenoid.

Well... since the power source was a whole 12g CO2 cartridge, I would have had to rebuild the whole thing longer. But on the bright side, I have already lined up some parts to regulate and monitor chamber pressure. I will be able to use it next year.

@Gipetto

Well... took the thing to event and was turned away because it was too powerful. Launched that Nerf pocket vortex at 220 fps.

I ended up taking a second HDPE circle, like the one under the barrel seal, and putting it behind the bumper/seal. Now since their was now no bumper, I cut 1/3 off of a tennis ball, drilled a hole in the other side, and installed that as the new bumper. Wouldn't you know... the darn thing works now....

@Gipetto... or anyone with constructive criticism... I took your advice and turned the bumper around, and replaced the sealing face gasket with a 1/8" rubber type gasket material cut to size. I got all the leaks worked out and fixed. Now the problem I am facing is that the piston hangs up right when...