20 replies to this topic

[Buffdaddy]

As many of you know, the Pulsestrike is one of the most awesome water guns for conversion to Nerf. With a pump replacement, it easily rivals the Titan in terms of power, but for much less money. A homemade version also requires perfect chamber sealing...something that's hard to achieve.

After several experiments with repair couplings and other things, I fell back to my first homemade writeup for inspiration. Instead of looking for a preassembled chamber, I would modify my earlier design of the piston inside the B.U.F.F. for better sealing. That, combined with an amazingly easy to open ball valve, made for a blaster with lots of power.

Parts list:

Blaster body:
1 1/4" PVC
1" to 1/2" PVC bushing
1 1/4" PVC tee
1/2" PVC
1/2" PVC tee (with the tee off threaded)
1/2" Sch. 80 PVC ball valve made by KBI

Internals:
(2) 3/4" PVC caps, with large hexagonal ends (made by Genova?)
3/4" PVC coupling
(2) AS568A-216 o-rings (1 1/8" ID, 1 3/8" OD)
Your choice of skirt seal/superlative plunger head/etc. Look them up.
(3) 3/4" PVC caps
(2) Hillman #49 springs

Pump/grip:
Whatever pump you choose, and the fittings required to convert to 1/2" Male threaded PVC

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Here's the new version of the internal piston. Under ideal construction, you would use a 3/4" coupling, and 2 3/4" plugs. Specifically, the kind with large hexagonal ends that you can shave down to fit ever so loosely into 1 1/4" PVC. In a nod to overengineering, I went ahead and added a skirt seal to the side that faces the barrel. Normally, I'd use polycarb circles and McMaster skirts, but none were handy. I improvised and took the skirt seal from a broken Marshmallow blaster, which fits perfectly in the 1 1/4" pipe.


Now we can place springs behind it. I used 3/4" PVC caps to keep the springs lined up to minimize issues. Pictured are Hillman #49 springs. Since then, I've nested other random springs inside the #49s. a 1 1/4" PVC tee will cap the back of the blaster, acting as the spring rest and the shoulder stock.


The main work is done. I capped the frot of the chamber with a 1" to 1/2" bushing (with a wrap of tape and JB weld). The bottom of the tee is threaded, allowing use of the Dual Action pumps from my Modular Air Gun System. on the front is a KBI 1/2" Sch. 80 PVC ball valve. Aside from the initial opening force, it is amazingly easy to open all the way - the result being performance like the spring-loaded ball valves in some Super Soakers. I'll throw a longer handle on there, so that I can use the bike pump as the grip and have a normal trigger.

Ranges? I'm still testing, and improving. There's currently no lube (need to do that ASAP), but it's sealing perfectly. 10 pumps fully compresses the springs, and firing is the most amazing sound I've heard from a homemade blaster yet. With a 2' CPVC barrel (hardly the best barrel material for airguns), I'm breaking 120', and there's STILL extra power available for a longer barrel. Needless to say, I think I have the design down pat.

UPDATE: My design allows for disassembly from the backside. Which means different spring combos. You can use a spacer to replace your extra springs!

Currently, the reduced volume and springs brings the ranges within reason. Still 100+, but similar to other homemade primaries. And I only need 5 pumps now; the UBER version needed 10 for full spring compression (and amazing power).

There are several issues to deal with:
-SHEER POWER. I was aiming for this kind of power; however, aside from a massive shotgun or rocket launcher, it has little nerf war use. Make it smaller, with one smaller but stiff spring (or precompressed spring, if for some reason, you only have a [k26] laying around...)
-OPV. There currently is none. I'm looking at the possibility of placing a tiny hole in the 1 1/4" PVC pipe. Presumably, once you've filled the chamber enough to pass that hole, it will bleed out, and the spring will seal it off again.
-Plunger padding: I need to do this ASAP, as there is a ton of force being applied. You will have to do it as well.

Firing video:
http://www.youtube.com/watch?v=Zwp_zPc33VQ

Questions/comments/flames can now proceed.

Edited by Buffdaddy, 20 August 2011 - 11:12 PM.

[arfink]

Believe it or not this is something I have been looking to do. I have one pulse strike and really like it for its ability to shotgun an unbelievable number of darts. I am currently looking at doing a project which would require two such tanks, but I was concerned about the length of the PS tanks and was thinking I'd have to look elsewhere. This should fit the bill.

One other thing that makes a pulse strike-styled tank very cool is that it's easy to use with a small portable electric air compressor. No OPV is required in my current test rig, because what I do is position a push rod and switch such that when the piston moves back far enough it will push the rod which is connected to the switch and the switch will open, turning off the pump. The push rod can be adjusted to turn off the pump on a shorter stroke of the piston to reduce power as needed. I usually tend to fill it all the way up so I can launch 20+ darts in a single massive volley.

I'd want to change up how the valve is configured for my build, since I want a more traditional trigger, but this will be extremely useful for my actually-a-shotgun double barrelled shotgun setup.

[Curly]

Holy Shnike. I don't know exactly how you intend to make your trigger, but a 3DBBQ check valve would work PERFECTLY. Those damn check valves are so helpful, they make good blast buttons if hooked up correctly. I would assume the pseudo plunger tube's volume is a variable in range. Finally, an airgun that is composed mostly of springer parts.

I think you've found your bolo gun.

[Buffdaddy]

After I thought about it, this design can already be shrunk. There's nothing to keep you from popping off the back and removing the springs inside. In all reality, you could just stick one spring in there, and then use some kind of spacer to fill the rest of the space.

BAM! this thing is as powerful as you want it to be Even if you only want a normal primary.

[Parallax]

Apologies for being dense - but how does this work?

I understand the basic principles of a back pressure tank but this design baffles me.

I'd love some clarity. Thanks.

[Curly]

Apologies for being dense - but how does this work?

I understand the basic principles of a back pressure tank but this design baffles me.

I'd love some clarity. Thanks.

It's not a BP tank at all. When you pump it air goes into the piston/plunger tube, and gathers pressure. When the pressure is high enough, the springs compress. You now have a plunger tube with compressed springs, AND higher than atmospheric pressure in the same space. When the ball valve opens, the air leaves the barrel, being pushed by the plunger as well. It's like a springer-airgun hybrid, with brutal power.

[lionhawk]

Sweet gun. I'm thinking with a long barrel and an empty rscb this could be a normal primary, while you can also make it amazingly powerful just for the fun of it/to show friends. Great job on this.

[chavez guy]

So just to clarify, this operates under the principle of the tank being both a plunger AND a compressed air tank? If so, then that is pretty cool.

[makeitgo]

Excellent work. I now have a use for all my sub-par water blasters that incorporate a spring loaded ball valve.

[arfink]

So just to clarify, this operates under the principle of the tank being both a plunger AND a compressed air tank? If so, then that is pretty cool.

Absolutely right. And I can say that for whatever reason you'll get more power out of that same volume of air than if it were just a plain springer or air gun. I do not know why this is.

[One long shot]

@arfink; It's probably because in this type of blaster, the entire volume of air is forced out of the barrel. A springer with the same volume would force all of the air out in the same way, but the pressure would lower because, fully drawn, there is still only one atmosphere inside the plunger tube. An air gun with the same volume would expel all of the excess pressure and you would be left with one atmosphere still left in the tank. This design combines the springer's forcing-out-all-the-air with the air with an air guns pressure-release system making for an efficient hybrid. But that's just my two-cents.

[Blue]

I like this a lot, and I think it's very cool what you did here. What are the O-rings for though? Stability of the PVC so it doesn't scratch the plunger tube? I guess this is more of an application for super soaker guns with spring loaded ball valves, but do you have any plans on making a homemade trigger? This also gave me a much better understanding of the shot blast type super soaker tanks. I can only imagine the sound it makes firing... giant airgun combined with massive spring force... no surprise you want to add padding. Anyways, keep up the great work with all these awesome homemades.

[Buffdaddy]

@arfink; It's probably because in this type of blaster, the entire volume of air is forced out of the barrel. A springer with the same volume would force all of the air out in the same way, but the pressure would lower because, fully drawn, there is still only one atmosphere inside the plunger tube. An air gun with the same volume would expel all of the excess pressure and you would be left with one atmosphere still left in the tank. This design combines the springer's forcing-out-all-the-air with the air with an air guns pressure-release system making for an efficient hybrid. But that's just my two-cents.

Pretty much nailed the explanation there.

I like this a lot, and I think it's very cool what you did here. What are the O-rings for though? Stability of the PVC so it doesn't scratch the plunger tube? I guess this is more of an application for super soaker guns with spring loaded ball valves, but do you have any plans on making a homemade trigger? This also gave me a much better understanding of the shot blast type super soaker tanks. I can only imagine the sound it makes firing... giant airgun combined with massive spring force... no surprise you want to add padding. Anyways, keep up the great work with all these awesome homemades.

The extra o rings are the result of over-engineering, quite frankly. With the new piston setup, it "should" seal with just the o-rings or just the skirt seal. But I went ahead and made the assumption that I'd mess up somewhere, and require extra sealing surfaces. The O-rings do help hold the piston in place, though, so it's not scratching up the tube.

And yeah, we've discussed this in IRC somewhat. Since the pump can be switched out and all that, there is the potential for using this for Nerf (any ammunition) and water blasting. I'm just going to delay that experimentation for now, until I grab another cheap super soaker that I can scrap for the water tank and pump.

[PVC Arsenal 17]

I never really thought about the possible advantages of pressurizing a spring-loaded chamber like this. I imagine the results would be similar to a chamber made of latex tubing (which may be easier to build). This is a great innovation for air powered blasters as efficiency can be increased while size can be decreased. Nice work.

If you replaced the ball valve with a QEV or something like that, you should be able to get the same power from an even smaller gun while creating a more ergonomic "trigger".

I may make a similar rig with a dual-acting air cylinder to test this concept and find an ideal balance between input pressure and air-spring pressure... On a similar note, I wonder how much performance could be squeezed out of a water hammer arrester.

Edited by PVC Arsenal 17, 18 August 2011 - 10:54 PM.

[Demon Lord]

I'm not going to lie, I both like this design and and terrified of it. I'm thinking I need to combine this design with your homemade nerf mortar set up and have one truly pants wetting siege blaster.

[Buffdaddy]

I never really thought about the possible advantages of pressurizing a spring-loaded chamber like this. I imagine the results would be similar to a chamber made of latex tubing (which may be easier to build). This is a great innovation for air powered blasters as efficiency can be increased while size can be decreased. Nice work.

If you replaced the ball valve with a QEV or something like that, you should be able to get the same power from an even smaller gun while creating a more ergonomic "trigger".

I may make a similar rig with a dual-acting air cylinder to test this concept and find an ideal balance between input pressure and air-spring pressure... On a similar note, I wonder how much performance could be squeezed out of a water hammer arrester.

I know, trigger trigger. I'll get to it....but yeah, some other options would be better. Heck, even a 3DBBQ style trigger would be fine.

I'm not going to lie, I both like this design and and terrified of it. I'm thinking I need to combine this design with your homemade nerf mortar set up and have one truly pants wetting siege blaster.

Yep. and technically speaking, you can scale up to a piston of 1 1/4" fittings and a tube of 2" PVC. I need to find the o-ring numbers you would use, but it's definitely possible.

[PVC Arsenal 17]

I found that you can get a good seal in 2" sch40 using a #9562K48 skirt seal. The fit is very tight, however. If you let the skirt seal sit inside the pipe for a while it might eventually conform. That plus good lubrication should make it work for this. Or, go straight to 2" ID polycarb tube and it'll work immediately.

Buff, would you consider making an equivalent test rig without the spring system to see just how much the spring helps? I think all of us would be curious to see the difference.

Edited by PVC Arsenal 17, 19 August 2011 - 04:49 PM.

[BOSS9]

I converted my SNAP into this (it has a perfect seal already), and man is that awesome. The ranges are incredible, even though I never built up much pressure- a [k26] is WAY too weak for this. To make it more awesome, I just added deadspace, or expanded the tank, depending on whether you're talking in springer language or airgun. I threw a 5-shot shotgun hopper on it and played with it most of the night. Props for the idea.

[Buffdaddy]

I found that you can get a good seal in 2" sch40 using a #9562K48 skirt seal. The fit is very tight, however. If you let the skirt seal sit inside the pipe for a while it might eventually conform. That plus good lubrication should make it work for this. Or, go straight to 2" ID polycarb tube and it'll work immediately.

Buff, would you consider making an equivalent test rig without the spring system to see just how much the spring helps? I think all of us would be curious to see the difference.

I actually should have rigs already made, I can just use the air tanks from my Modular airgun system, swap out the garden nozzle, and try it out. Will have to measure out/estimate volumes, but I'd certainly be glad to do so.

I converted my SNAP into this (it has a perfect seal already), and man is that awesome. The ranges are incredible, even though I never built up much pressure- a [k26] is WAY too weak for this. To make it more awesome, I just added deadspace, or expanded the tank, depending on whether you're talking in springer language or airgun. I threw a 5-shot shotgun hopper on it and played with it most of the night. Props for the idea.

With my nearly non-existant background in homemade springers, this thought never occurred to me, taking a SNAP and throwing a pump on the side. In all reality, you could again take the pump on and off, and possibly switch between pulse mode and normal springer. I'm going to have to try this now, once I finally get around to building SNAPs.

[arfink]

With my nearly non-existant background in homemade springers, this thought never occurred to me, taking a SNAP and throwing a pump on the side. In all reality, you could again take the pump on and off, and possibly switch between pulse mode and normal springer. I'm going to have to try this now, once I finally get around to building SNAPs.

That would make it a true hybrid weapon. A traditional springer with a pulse strike option? Heck yes!

[BOSS9]

That would make it a true hybrid weapon. A traditional springer with a pulse strike option? Heck yes!

In my tests, with a normal ball valve and tee to attach a pump (I used a 1/2" plug in the tee with vinyl tubing going to the same pump buff used, but unmodified), and the minimal amount of piping to attach things, I still got good primary ranges using the snap with a hopper. It could be used as a high ROF ~100' primary with a ridiculous range backup, but in one gun! And if you just attached the ball valve directly o the PT and drilled a hole for tubing, almost all deadspace would be removed, giving you much better springer ranges. I feel like to increase reliability, the plunger head needs to be modified. my superlative head needed to be re-lubricated to maintain the seal. I'm thinking something like Venom's homemade pump head (http://nerfhaven.com...ndpost&p=301385), but for 1 1/4".

Edited by BOSS9, 20 August 2011 - 04:41 PM.