8 replies to this topic

[Buffdaddy]

This issue has bugged me since summer, after several failures at making a semiautomatic airgun.

My need: ways to construct/buy valve that, once said pressure is reached, diverts pressure to a reserve tank. This would have to be operated by compressed air, presumably by a feedback line from the firing tank side of the valve. Essentially, a 3-way pilot valve.

I'm still searching the interwebs, but I'm having trouble finding anything that won't be half the price of the end blaster.

Cheapest I could possibly use thus far(?????): 3 way valve

I know it's an odd question; I just want to see if what I'm imagining is possible (or practical).

CLARIFICATION: I know you could use a side-venting OPV. My issue is that I want the capability for the reserve tank to be at a higher pressure.

EDIT: For the moment, I'm settling on an alternative design using small shutoff valves. It'll mean consecutive shots will weaken, but it also gives me the option of shutting off the reserve tank, if I don't have time to pump it all the way up (i.e. it's empty, I'm being rushed, and I need good shots NOW).

Edited by Buffdaddy, 15 October 2011 - 11:17 AM.

[spencerak]

Dyxlesic made a semi-auto firefly here that used a valve, and a regulator from a separate tank to a big salvo tank.

[Buffdaddy]

That's still not quite what I'm aiming for - that still requires you to charge up a tank prior to firing, and I want to retain the ability to only need a couple pumps for a quick shot. In a sense, I want the ability of semiauto without making it a necessity.

Given that I have some time, I'll go with the valve posted earlier. If it arrives soon enough, I'll have this concept tested at HbH.

[Curly]

I think your best bet it attaching the pump feed to a Tee which has the pilot and blast button on one side, and a ball valve leading to another. The "another" will have the reserve tank behind it. When you want to use only the firing tank close the valve, and to use semi-auto and fill the second tank open it.

Unfortunately that would require manual activation, though it's very cost-friendly. If you want the reserve to not have a free-flowing connection to the firing tank(holding the blast button will slowly dump the reserve) look near those pop safety valves on Mcmaster. I'll keep my eye out.

[Zorns Lemma]

I'm still searching the interwebs, but I'm having trouble finding anything that won't be half the price of the end blaster.

Cheapest I could possibly use thus far(?????): 3 way valve

It's going to pretty hard to find the valve you're looking for on the cheap. As you've probably learned in the IRC no passive system will vent air from lower pressure to higher pressure so you basically need a switching system.

The valve you posted seems to do the job pretty well.

But something else you could look at are automatic shutoff valves in conjunction with a pressure actuated valve so that the path to your firing tank turns off at x psi and then the path to your shutoff opens at x psi.

Either way though, there's no real avoiding the fact that if this is routed from the pump, you'll have to pressurize the tubing to 25 psi before you can start filling the reserve.

[shmmee]

I spent quite some time trying to develop a semi auto valve. I was trying to use a tee with a plunger sliding back and forth between the middle leg to fire a back pressure tank.It was having seal issues. My next step was to try building this:


It's based off of two reversed oprv pop valve to make a pull pin blaster with a pull pin reserve tank.

It was never made due to lack of funds and parts. Yeah, I'm presenting an unproven concept, but feel justified in doing so because of the open ended nature of the topic.

I gave up on development and bought a marshmallow M forcer (20 shots, semi auto, rear loading) from drugstore.com. Just needed PTEG barrels and a pump replacement.

Edited by shmmee, 15 October 2011 - 07:12 PM.

[roboman]

Honestly, $17.60 isn't a bad price for what you're asking. In fact, that's probably about as cheap as you'll be able to go - even I would charge more than that to make what you're looking for.

[238232]

I'd vote for Zorn's idea, but with one small addition. Use a hybrid air tank like the one in a Quick Blast or Shot Blast. As the pressure in the tank is increased the plunger gets pushed back, perhaps this can be used to trigger valves to reroute air? With some good design, when the tank is fired it could refill itself and automatically cut off when it's full.

[Buffdaddy]

Update: AFter doing enough searching, Clippard has the pieces I'm looking for (all miniature). They have the air regulator from Dyslexic's thread, plus some of the air piloted valves discussed earlier, for decent shipping. A bit expensive for an overhaul, but it should all be worth it. Once I have the money to do it.

Thanks for your help!

Edited by Buffdaddy, 17 October 2011 - 02:04 AM.