20 replies to this topic

[TantumBull]

I've been mulling this idea over for a while, but I never really executed it until recently. As we all know, homemade check valves are about the easiest thing in the world (Zorn made people, who hadn't already, realize this). Why not go a step further and make an OPRV? All you need is a stronger spring!

What you will need to do this effectively:
-something to test presser with (I used the pressure gauge attached to my LS)
-a pump
-a pen
-and airsoft BB
-some fairly strong smallish springs, I just got some industrial strength one at Ace
-1/4" OD, 1/8" ID vinyl tubing
-super glue
-barbed tee
-barbed coupling (optional)

(barbed fittings not shown)

I'm not going to do a full step-by-step write up, as the pictures should really explain everything. I'm more just going to go into some basic concepts.

First, here's and equation that Zeke came up for me a while back, to figure out the required spring constant and pre-load on the spring for a certain PSI (I'm fairly certain that the only units in this equation are inches, so don't worry about any conversions):

(spring constant)(pre-load in inches) = (psi)(area of sealer)

Now if we are focused a certain PSI, we set it up like this:
(psi) = ((springconstant)(pre-load)) / (area of sealer)

If you're using my set-up, you can assign 1/8 for (area of sealer), as that much of the BB will be sealing on the vinyl tubing.

Now, I never actually got around to using this formula, I just bought some springs and tried them out in a not fully glued together valve. I highly recommend this, as guessing and checking is far more reliable in this case. The formula comes into play if you're ordering springs online.

Here are some pics now:



Now, here's how you're gonna get the PSI you want. You're going to NEED a pressure gauge at your disposal.


Mutilate the pen to get the tube. Glue in a segment of tubing on one end. If you're using a barbed fitting, it doesn't need to be very long. This will be your air input end.

Now put in the BB, and then the spring. Put a segment of vinyl tubing in last, and compress the spring a bit. DO NOT glue the tubing in on this end, or you won't be able to find the desired pressure. Hook up the air input to a tee, with the other two airways connected to your pressure gauge and pump.

Pressurize the valve. Hopefully the pen tube will grip the tubing well enough that it won't shoot out or leak too much when you pressurize the valve. It'll leak a little, but it'll still work for the testing phase. The pressure on the valve will spike, and then jump down. Wait until you don't hear/feel (by plugging the end with your thumb) any more air exiting the valve. Record the pressure shown on the gauge. Rinse and repeat, but adjust the tubing in the air outlet for different pressure levels. Here's a pic to help you with your testing:


Once you get the pressure you want, mark how far the vinyl tubing is into the pen body. Apply glue, and put it to the marked length. There you go, you're done.

The valve in this write-up releases air at about 45 PSI. It was made for use on a RSCB'd 4B, as shown below.


Now you can loan your air guns out without having to worry.

What do y'all think?

Scroll down for update!

Edited by TantumBull, 17 October 2009 - 01:12 PM.

[JATDO]

This is amazing. Worry free air guns
How much do you think it costs per a valve?

[Draconis]

To buy all the parts new? $5? Pretty much free if you have tubing and a couple of pens. You could also use other balls instead of the airsoft bb, if you don't have those. Great design Tantum. Far less expensive than McMaster's valves.

[Zorns Lemma]

The only issue is that past 50psi you start running into some structural issues. With the ones I've build, they have a tendency to shoot part of the valve off.

You might want to try welding the parts together because super-glue has miserable shear strength.

[TantumBull]

This is amazing. Worry free air guns
How much do you think it costs per a valve?

Thanks, yeah, that's the thought. If you start with nothing and buy in bulk off mcmaster, costs shouldn't be over 4 or 5 dollars.

To buy all the parts new? $5? Pretty much free if you have tubing and a couple of pens. You could also use other balls instead of the airsoft bb, if you don't have those. Great design Tantum. Far less expensive than McMaster's valves.

Thanks. Yeah, I was gonna order an OPRV off there but the price dissuaded me a bit.

The only issue is that past 50psi you start running into some structural issues. With the ones I've build, they have a tendency to shoot part of the valve off.

You might want to try welding the parts together because super-glue has miserable shear strength.

Thanks for the suggestion, point noted. When/if I run into this issue I'll get a hold of some solvent weld.

Edited by TantumBull, 28 September 2009 - 10:16 PM.

[Draconis]

This is amazing. Worry free air guns
How much do you think it costs per a valve?

Thanks, yeah, that's the thought. If you start with nothing and buy in bulk off mcmaster, costs shouldn't be over 4 or 5 dollars.

To buy all the parts new? $5? Pretty much free if you have tubing and a couple of pens. You could also use other balls instead of the airsoft bb, if you don't have those. Great design Tantum. Far less expensive than McMaster's valves.

Thanks. Yeah, I was gonna order an OPRV off there but the price dissuaded me a bit.

The only issue is that past 50psi you start running into some structural issues. With the ones I've build, they have a tendency to shoot part of the valve off.

You might want to try welding the parts together because super-glue has miserable shear strength.

Thanks for the suggestion, point noted. When/if I run into this issue I'll get a hold of some solvent weld.

If you could locate a pvc tube. then you can weld the vinyl tube to it with cheap pvc pipe weld.

[imaseoulman]

Over all, not a bad design. Now what we really need is a cheap homemade pressure regulating valve.

[TantumBull]

Over all, not a bad design. Now what we really need is a cheap homemade pressure regulating valve.

Thanks. And its funny you say that, I was just thinking that same thing yesterday evening.

[ggk]

Would venting the over pressure release valve back to the tank make a makeshift regulator?

[TantumBull]

No, it would just make for each pump stroke being really hard. This valve stays open at higher pressures and closes at lower pressures. Regulators stay open at lower pressures and close at higher pressures.

NB: Higher and lower are just relative values.

[TantumBull]

Update!
Pressure levels are now adjustable on the fly! I really don't know why I didn't think of this before.

First, drill a hole to vent pressure. The back will now be plugged by a screw, so you need a holde for pressure to vent.


Now, cut down a fatty screw and just screw it in. Loosen for lower pressure levels, tighten for higher levels. The brass is there to tighten the pen tube, I didn't have a wide enough screw on hand.

[Fome]

Absolutely brilliant

[wingd man]

Wow. Why aren't you a Contributor yet?

This gives me an idea though, say you wanted to have a split fire, but with 2Ks. If you were to attach one 2K to an OP, with the "dump" end attached to another 2K, you could pump one up without the other if you wanted, but could also pump both up for a 2-shot effect.

[CA13]

Sounds like my idea for a Jobar or Cobra with a Hornet/SMDTG integration. This thing is cool, and I'm starting to think about putting one on a BBBB with a Hornet integration. Could you use a cross-coupler at the end and possibly fill 3 sets of tanks?

[TantumBull]

Wow. Why aren't you a Contributor yet?

This gives me an idea though, say you wanted to have a split fire, but with 2Ks. If you were to attach one 2K to an OP, with the "dump" end attached to another 2K, you could pump one up without the other if you wanted, but could also pump both up for a 2-shot effect.

Thanks. No, that would not work how you think it would. It would just be adding a check valve with a really high cracking pressure between the tanks. Lets say you set the OPRV to 50 PSI. You start pumping, and air goes into the first tank. Once that tank hits 50 PSI, air begins to be vented into the other tank. Once the second take hits 50 PSI, they both start filling up simultaneously to higher pressures.

I'm fairly certain that's what would happen with your set-up. Maybe the OPRV would crack at a higher pressure because of the added force on the sealer (pressure from second tank), but other than that, I'm pretty sure this is what would happen.

Sounds like my idea for a Jobar or Cobra with a Hornet/SMDTG integration. This thing is cool, and I'm starting to think about putting one on a BBBB with a Hornet integration. Could you use a cross-coupler at the end and possibly fill 3 sets of tanks?

I'm not familiar with Jobar/Cobras and what kind of valves they have. As for your question, I have no idea what you're talking about. When thinking up possible configurations, just remember that this valve will act as a check valve that cracks at a high pressure relative to check valves.

[wingd man]

Sorry if I didn't explain well, but that was the idea.

[TantumBull]

Sorry if I didn't explain well, but that was the idea.

Ah, my apologies than. That actually isn't a terrible idea, as I believe it would prevent air venting from tank one upon firing tank 2. Then just throw in an additional valve in tank 2 to regulate the pressure of the whole assembly.

[TantumBull]

Ah, thanks for clearing that up. I was wondering about the force added from pressure in the second tank, although I never thought that it would so directly affect the cracking pressure.

[wingd man]

You mean because the pressure from the second tank pushes the ball bearing back so it increases the cracking pressure?

So if you were to do it with, say, a titan, then an AT2K, and then a hornet tank, it might work?

Edited by wing'd man, 19 October 2009 - 08:53 AM.

[TantumBull]

You mean because the pressure from the second tank pushes the ball bearing back so it increases the cracking pressure?

So if you were to do it with, say, a titan, then an AT2K, and then a hornet tank, it might work?

Those tanks have different volumes, not different safe operating pressures.

[Zorns Lemma]

Ah, thanks for clearing that up. I was wondering about the force added from pressure in the second tank, although I never thought that it would so directly affect the cracking pressure.

Pressure = Force/Area. The spring provides sealing force. The second tank provides sealing force. Ergo, as pressure goes up in the second tank, it requires more pressure in the first tank to open the valve.

You mean because the pressure from the second tank pushes the ball bearing back so it increases the cracking pressure?

So if you were to do it with, say, a titan, then an AT2K, and then a hornet tank, it might work?

Those tanks have different volumes, not different safe operating pressures.

Hornet > At2k > Titan in terms of regular operating pressure for the ranges most people try to get out of them.

You can put this on a zaxblast and thus get your BS tanks at 60 PSI while keeping the BBBB at 20 PSI by making a valve that cracks at 40 PSI.
That way your BS tanks can actually hit things, but the 4B isn't shredding darts and putting holes in people.