2 replies to this topic

[BlackFox]

For practical integration purposes, I decided it was necessary to make an at2k which could be completely filled with only one pump. Just as a heads up, my finished mod doesn't work, but I see no reason why it doesn't.

The first and most important piece you'll need is the pump. Unfortunately, all I've got for you is this picture.

I picked it up at a second hand store and it has nothing to identify where it came from, but it is perfect nonetheless. It's not too big and has a huge air output because it pumps out on both the draw and compression.


Cut off the check valve from the original pump leaving about half an inch of the pump tube left on the end. And specifically for this pump, cut 1.5" of CPVC to cover the tip.


Sand down the base of the tip on the pump until the CPVC can slide over it and fill the dead space with hot glue. A tiny bit of sanding may be needed around the inside of the check valve for the CPVC to fit inside as well. Once everything fits, put plumbers goop at both ends of the CPVC. From here it's just a matter of gooping everything together. (It looks like the check valve is in tatters from the picture, but I replaced it so it works like new and kept the old pic.)



Goop down the appropriate length of vinyl tubing to suit your purposes.


This is as far as I went. At this point, the gun should work. The tank doesn't take the full volume of air the pump can deliver. I did not goop the check valve to the CPVC so I could make adjustments and I know that sounds like an obvious explanation, but it isn't causing the problem. It isn't leaking, it's as if the tank is full and won't take in any more air.
-The check valve is in perfect working order
-The tank is taking some pressure. Pulling the pin fires about the volume of a half pump from the stock pump.

So what am I doing wrong? Is a one pump 2k even possible? The best explanation I have is that the volume of air is so great that the check valve is just staying open effectively doing nothing leading me to believe that's why all other pump guns use a series of small pumps.

[imaseoulman]

Possible problem...you're not building up enough pressure. With a pump that wide (diameter) it takes a lot of force to comress the air to 40 psi. If you are pushing a pump that has 1" diamter, reaching 35 psi isn't too tough. But if the pump has a diameter of 2.5", reaching 40 psi takes a bit more effort.

Remeber, PSI stands for pounds per square inch, which is surface area. The greater the surface area of your pump head, the harder it is to pump at higher pressures.

So if it's hard to push and feels like it is fully pressurized, it probably actually isn't. That pump doesn't look like it could get much more than 10 PSI out of it. I'm pretty sure it's for inflating things like balloons or maybe even an air mattress, which is typically around 8 psi.

[BlackFox]

imaseoulman, on Nov 16 2008, 06:29 PM, said:

Possible problem...you're not building up enough pressure. With a pump that wide (diameter) it takes a lot of force to comress the air to 40 psi. If you are pushing a pump that has 1" diamter, reaching 35 psi isn't too tough. But if the pump has a diameter of 2.5", reaching 40 psi takes a bit more effort.

Ah- that is a problem.
In all honesty, I was planning on using this as an integration in my recon. With the stock pump, it would require priming the breech and pumping the tank. I was hoping to attach the pump to the slide on the recon to eliminate one step, but it looks like that won't be happening now.