24 replies to this topic

[TantumBull]

Just a word of warning: this mod involves cutting apart a salvo valve. If you don't feel comfortable doing this, than I suggest you not do this, as it is fairly easy to screw up your valve.

Alright, first step. Simply cut open the valve as shown with a saw. Use one with the thinnest blade you can find.


Remove the innards and look down into the casing. This is what you'll see:


Do you see that little ridge? That is what the piston seals against. It's completely safe to widen that hole but not go past the ridge. My actual valve opening wasn't concentric with the sealing ring, so I could just drill a bigger hole. I used a smallish drill bit on my dremel and carefully shaved away plastic until I hit the ridge. Finished hole:


Now just solvent weld everything back together and you have a much more efficient big salvo valve. Don't forget to put the piston back in before doing so!

Edited by TantumBull, 18 January 2010 - 07:22 PM.

[Banshee]

Sweet! What kind of extra power are you getting out of this?

[TantumBull]

Sweet! What kind of extra power are you getting out of this?

I actually haven't tested ranges yet, but I'd be happy to tomorrow when the sun is up. I didn't earlier because some goop was drying on a leak in the tubing area (I make a lot more mistakes when modding at 2 in the morning).

[bourbon]

I assume this would work for the Hornet and SMDTG as well, with their air powered backflow valves. What about the Secret Shot 2 and the Lightning Blitz? These guns have air powered valves as well, but they are activated by different means. At the very least, the valve opening could be enlarged.

If the increase in power and efficiency is significant, I will try this on the spare SS2 tank I have in my parts drawer. Based on how effective the "airflow mod" is on AT2Ks, it could increase range by as much as 10%. Please post your results as soon as you get the chance.

[nisaburo]

Very nice work, I really enjoy these somewhat subtle mods that potentially add a lot to overall performance. Do you think this could be applied to other back pressure valves? You may have helped solved a problem I had with a BPV repair by pointing out the circular ridge that makes the seal.

Off topic: Haven't been able to properly test the spacers yet, I need some more PETG to become available.

[TantumBull]

I assume this would work for the Hornet and SMDTG as well, with their air powered backflow valves. What about the Secret Shot 2 and the Lightning Blitz? These guns have air powered valves as well, but they are activated by different means. At the very least, the valve opening could be enlarged.

If the increase in power and efficiency is significant, I will try this on the spare SS2 tank I have in my parts drawer. Based on how effective the "airflow mod" is on AT2Ks, it could increase range by as much as 10%. Please post your results as soon as you get the chance.

It potentially could, but it really depends on how the piston seals, how big the piston is, and if it does similarly to a big salvo, then it would also depend on how big the opening is in comparison to the "sealing ring". Before opening your SS2, take a look at the dissection thread, I seem to remember an SS2 tank in there.

Very nice work, I really enjoy these somewhat subtle mods that potentially add a lot to overall performance. Do you think this could be applied to other back pressure valves? You may have helped solved a problem I had with a BPV repair by pointing out the circular ridge that makes the seal.

Off topic: Haven't been able to properly test the spacers yet, I need some more PETG to become available.

Thanks, man. Like I said above, it really just depends. I'm sure you could do something to most of the other valves to increase airflow, but I'm not sure if the method would be identical to that of the BS.

And tell me how those work out when you get some PETG.

[bourbon]

I found the following Lightning Blitz thread by doing a site search for "disect tank".

LB Disection

Based on the pictures in this thread, it seems that the rubber sealing gasket in these tanks are much larger in diameter than the air outlet they cover. I'm willing to bet that the holes could be enlarged significantly. This could be a much bigger deal than you realize.

The SS2 and LB are 12 year old guns, and not exactly easy to acquire. Since I have three of each, I'm willing to try it out on one of them. If this mod can be performed, and the results are favorable, it proves that this modification can positively affect a huge number of guns. The Blastfire, Hornet, LB, SS2, and the Big Salvo just off the top of my head. The Hornet especially could benefit from reduced pumps.


Big edit. The modification can be done to the SS2. TB, if you feel this is derailing your thread at all, let me know and I'll save it for my upcoming SS2 write-up. You would be credited for this aspect of the mod of course.

I may be wrong but this may be the first time the SS2 tank internals have been photographed.







As you can see in the following picture, I was able to enlarge the air outlet significantly. I used the largest drill bit I had on hand, and the hole is now 3/8". A little bit of sanding, and it seals perfectly.

Edited by bourbon, 17 January 2010 - 12:27 AM.

[Hipponater]

Very interesting, I'd like to see the ranges as well, to know if it's worth the risk, but it really looks to be a good mod overall.

I enjoy efficiency, so reducing that volume was a pretty neat idea. What kind of pipe is your 'plastic pipe'?

[nisaburo]

The SSII tank is actually the one I was attempting to repair. Bourbon, I think you might have a problem. In your last picture it looks as if the piston head is inserted into the hole. If that is the case I don't think the tank will be able to fire at all. Once the pressure behind the piston is released to fire the tank the piston head would still be stuck in the front hole.

[bourbon]

The rubber gasket has a diameter of 1/2", pretty much identical to the ID of thinwall PETG. I toyed with the idea of replacing the black plastic piece with PETG halfway through the process, but it was able to slip through.

I assure you that the 1/2" gasket cannot fit through the 3/8" opening. The rubber simply doesn't have enough give. I tried to push it through before writing this post, and it wouldn't budge.

I have no super glue at the moment, so I'll have to reassemble the tank tomorrow. Hopefully TB will have ranges by then, and we can see if hacking these tanks open is worth it.

Out of curiosity, what epoxy are you using to put your tank back together Tantum Bull? I superglue my halves together and then smother the seam generously in Goop. It's a real pain in the ass, but the epoxy I have doesn't work, it just won't grip the plastic.

[Soothsayer]

That's the whip dude!
I've always had trouble with big salvo tanks, usually like 1 or 2 of the 4 are a little shitty, but this definitely just perfects them all into cannons.

Great work!

[nisaburo]

The rubber gasket has a diameter of 1/2", pretty much identical to the ID of thinwall PETG. I toyed with the idea of replacing the black plastic piece with PETG halfway through the process, but it was able to slip through.

I assure you that the 1/2" gasket cannot fit through the 3/8" opening. The rubber simply doesn't have enough give. I tried to push it through before writing this post, and it wouldn't budge.

I have no super glue at the moment, so I'll have to reassemble the tank tomorrow. Hopefully TB will have ranges by then, and we can see if hacking these tanks open is worth it.

Out of curiosity, what epoxy are you using to put your tank back together Tantum Bull? I superglue my halves together and then smother the seam generously in Goop. It's a real pain in the ass, but the epoxy I have doesn't work, it just won't grip the plastic.

Ah, I see. I just misread the pictures then. For both you and Tantum I would suggest Plastruct Plastic Weld General Purpose Plastic Solvent Cement. I have repair several tanks but cleaning the cut and then applying a generous amount of solvent and holding the two parts together. Wait a few seconds for it to start to cure then apply another layer around the seam/joint. Repeat several times until there are no visible holes. Let the whole thing sit for a few hours and then pressure test. I have yet to have any leaks from joins made this way.

[Draconis]

Great idea Tantum, but you may be making the wrong recommendations for adhesives. Epoxies are certainly better for the reassembly of pressure tanks than, say, Goop, or something... But to be honest, I wouldn't trust any tank at pressure unless it was assembled by solvent welding. For pretty much ANY back pressure tank, you should be able to use PVC/ABS pipe weld, which is inexpensive and available at any hardware store.


EDIT: Oh, Ha! Nisaburo had already suggested this. Sort of.

Edited by Draconis, 17 January 2010 - 01:13 PM.

[TantumBull]

Bourbon: Great job on the SS2, it's great to see this works on it. And of course you can post your successes with this mod here, it would be great for everyone to know what this has been tested on. Oh, and about smaller tanks like hornet ones, the deadspace removal doesn't really apply, as the pilot portion of the valve is pretty much as thin as it can get without causing problems from a too-low flow rate. You may be able to get rid of a little, but the dead space removal part of the mod probably wouldn't be worth the effort.

Hipponater: Thank you, and the pipe was from the internals of some slime-shooting super soaker. Kind of an obscure part.

Bourbon again: The epoxy is Devcon General Purpose Epoxy. Be sure to mix it really thoroughly. That's the number one reason for epoxy failure.

Soothsayer: Thanks, man!

Nisaburo: Point noted about the solvent weld. I'll do that if/when the joint fails.

Draconis: Thanks, and same as above. I'll also edit the write-up.

Everyone: I'll try to get ranges up by today. I have some stuff to do right now, but I'll be sure to get to it later.

Edited by TantumBull, 17 January 2010 - 02:34 PM.

[Zorns Lemma]

Nice job on widening the valve, but I'm not sure if cutting out pilot volume was a good idea. When you test this, can you compare valve reliability at high pressures along with simple ranges?

[Draconis]

Bourbon: Great job on the SS2, it's great to see this works on it. And of course you can post your successes with this mod here, it would be great for everyone to know what this has been tested on. Oh, and about smaller tanks like hornet ones, the deadspace removal doesn't really apply, as the pilot portion of the valve is pretty much as thin as it can get without causing problems from a too-low flow rate. You may be able to get rid of a little, but the dead space removal part of the mod probably wouldn't be worth the effort.

Hipponater: Thank you, and the pipe was from the internals of some slime-shooting super soaker. Kind of an obscure part.

Bourbon again: The epoxy is Devcon General Purpose Epoxy. Be sure to mix it really thoroughly. That's the number one reason for epoxy failure.

Soothsayer: Thanks, man!

Nisaburo: Point noted about the solvent weld. I'll do that if/when the joint fails.

Draconis: Thanks, and same as above. I'll also edit the write-up.

Everyone: I'll try to get ranges up by today. I have some stuff to do right now, but I'll be sure to get to it later.

I doubt this will increase the ranges at all, because you aren't changing the dimensions of the tank itself, just the area behind the valve. The only real improvement you will see is from the amount of pumping that you have to do to reach the same pressure. Certainly an improvement for rate of fire, but not range.

[Hipponater]

I doubt this will increase the ranges at all, because you aren't changing the dimensions of the tank itself, just the area behind the valve. The only real improvement you will see is from the amount of pumping that you have to do to reach the same pressure. Certainly an improvement for rate of fire, but not range.

The part that may affect the ranges is increasing the flow of air out of the tank. Widening the hole to the ridge will hopefully allow air to release faster.

The removal of the dead space likely won't affect the ranges, like you said, only require less pumping. Or give you a little more pressure for the same pumps. But Zorn's Lemma raises an interesting point at how well the tank will function, it would be great if you could test that as well, Tantum.

[TantumBull]

Zorn: Thank you, and you raise a very good point about the piloting volume, one I should have thought of earlier. Fuller explanation is below.

Drac: I know that removing pilot volume won't increase range. I may have worded my response to buorbon incorrectly.

Hipponater: Functionality results below.

Bob: Thanks for the visual reinforcement, that's what I seem to remember about the pilot volume on hornet tanks.

Alright guys, no range testing yet, but I tested functionality:
At 30 PSI, it functions fine. Anything higher and the valve sputters out air, sounding like a dying animal. Zorn was absolutely correct, the volume is there for a reason: to provide enough of a vacuum to pull back the large piston fast enough. I just ripped out the tubing assembly and will be putting the stock tubing connection point back on or something equivalent. Sorry guys, it may be another day before ranges get posted. I've also edited the write-up to get rid of this embarrassing step.

[bourbon]

Hey Bob, since you've already got that hornet tank open, are you willing to test if you can widen the air outlet succesfully?

If it doesn't work, at least the hornet died in the name of science.

[TantumBull]

Mod doesn't work in it's current state. Valve still farting. I think the larger sealing face is causing some problems. Only solutions I can think of are using monster tubing and a larger pilot valve or increasing volume in the pilot portion of the tank. In other words, proceed at your own risk, and don't try it on a salvo till I or someone with one to spare get this figures out. Bourbon, hopefully you r SS2 valve isn't ruined.

[bourbon]

Mod doesn't work in it's current state. Valve still farting. I think the larger sealing face is causing some problems. Only solutions I can think of are using monster tubing and a larger pilot valve or increasing volume in the pilot portion of the tank. In other words, proceed at your own risk, and don't try it on a salvo till I or someone with one to spare get this figures out. Bourbon, hopefully you r SS2 valve isn't ruined.

ok, so you didn't take into account the tanks ability to "vacuum" the pin back. There has to be a way to make the vacuum stronger. On my SS2 valve, I filled the hollow part on the pin with hot glue (see picture 4, that hole on the white plastic pin, I don't know the terminology fo backpressure systems). I'm hoping that by removing this dead space, it will provide more suction.

On your valve, you lowered the volume of the pilot tank itself, which weakened suction. I'm hoping that on mine, filling that pin increases the suction power on the pin. Remember the straw mod on the maverick, how he filled in the inverted plunger? That allowed the maverick to compress air better because when the plunger was at the end of it's travel, there was no where else for the air to go. I'm hoping by filling this pin in, the vacuum created by the pilot tank emptying will pull on it harder. The volume of air acting on the pin is the same, but the surface the vacuum is acting on is much nearer to the backpressure exit valve (the hole the trigger opens. again, what do I call this). Logically it should increase the vacuum somewhat.

We don't typically work with vacuums in nerf, so I could be wrong, but I have to try something. check you big salvo valve for the same piece. Worst case scenario, we might have to actually find a way to expand the pilot tank. While this is the opposite of your original goal, is a couple more pumps for 10% more power that bad of a trade-off? the tank is ruined anyways, you have nothing to lose. Ch[font=Arial]

[TantumBull]

ok, so you didn't take into account the tanks ability to "vacuum" the pin back. There has to be a way to make the vacuum stronger. On my SS2 valve, I filled the hollow part on the pin with hot glue (see picture 4, that hole on the white plastic pin, I don't know the terminology fo backpressure systems). I'm hoping that by removing this dead space, it will provide more suction.

Most of this is addressed below.

On your valve, you lowered the volume of the pilot tank itself, which weakened suction. I'm hoping that on mine, filling that pin increases the suction power on the pin. Remember the straw mod on the maverick, how he filled in the inverted plunger? That allowed the maverick to compress air better because when the plunger was at the end of it's travel, there was no where else for the air to go. I'm hoping by filling this pin in, the vacuum created by the pilot tank emptying will pull on it harder. The volume of air acting on the pin is the same, but the surface the vacuum is acting on is much nearer to the backpressure exit valve (the hole the trigger opens. again, what do I call this). Logically it should increase the vacuum somewhat.

Read through the thread. I put the pilot volume back to how it was normally, same problem. And you're incredibly wrong thinking that will increase pressure on your pin. The pressure is equalized throughout the entire valve, its not going to be any greater in the piloting portion. All you did was decrease volume so that it fills in less pumps. Also, the straw mod doesn't even come close to applying here. With that, you're decreasing the volume that pressure (from a source that's a constant) goes through, thus pushing pressures up. With an SS2 you're limited to a max pressure to for safety, so decreasing volume just means less pumps, not higher pressure. Also, you said at the beginning you were "filling the pin". Not in any way, shape, or form will that keep the volume the same.

We don't typically work with vacuums in nerf, so I could be wrong, but I have to try something. check you big salvo valve for the same piece. Worst case scenario, we might have to actually find a way to expand the pilot tank. While this is the opposite of your original goal, is a couple more pumps for 10% more power that bad of a trade-off? the tank is ruined anyways, you have nothing to lose.

It's all relative actually (from the perspective of the pressure behind a dart while firing, the air in front of the dart is a vaccum), but I get what you're trying to say.

[bourbon]

so you're saying that no matter what we do, this design simply can't handle pulling back the pin when the hole is enlarged?

I'll pull out the hot glue thing. Let's just hope that it is able to work on mine. Does the Big Salvo pump really fill those tanks to 30 PSI? Try it at 25 or 20 maybe. My unmodified SS2 tank (just AR removed) farts air when I pump it 20 times, I can only go up to 16 before it stops opening properly. This problem might be exagerated in the modified tank.

[TantumBull]

I'm saying this doesn't work in it's current state. I'm going to try adding more volume to the pilot section within a week or two. I'll post my results here. And bourbon, I normally take salvo tanks up to 60 PSI with the salvo pump.

[bourbon]

Here's a thought. Technically, the tubing is still part of the pilot tank. You could put the release valve further down the line. That's probably how the hornet pulls it off even with those pitifully small pilot tanks.

The pilot tank on the SS2 is pretty big, I'm going to go ahead and glue it back together. If it doesn't work, I can probably revert the hole to the regular size with epoxy putty and drilling.