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Homemade air bladder

Constant pressure system for airguns

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#1 Just582

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Posted 10 November 2013 - 02:27 AM

So, I am looking to mod a at2k and at3k to make them semi auto by adding an air bladder, like in the magstrike. Basically make a constant pressure system with regulators and stuff. I don't really want to go buy a magstrike or rf20 for its air bladder. Has anyone experimented with the rubber tubes on McMaster as a replacement air bladder? I don't want to go buying a whole bunch of tubes, so I want figure out a good place to start at least. I do not own any blasters with these rubber bladders, so I can't even begin to figure out what kind of rubber is being used.
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#2 shmmee

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Posted 10 November 2013 - 05:20 AM

Oh dear, where to start...

I've spent a lot of time chasing the perfect semi-auto platform. To start with the origional question asked:
I once went to my local EVCO house of hose and bought some varied diameter latex tubing. After having a foot or two of odd sizes rung up I would call it cost prohibitive. The nerf bladders use foam latex. I think it has a higher ductility that straight latex (surgical tubing) and therefore more fills. In discussing the materials with Doom (he's spent a lot of time with them in water blasters) I also learned that when an air filled latex bladder ruptures, it 'splodes as loud as a shotgun and might draw unwanted attention. I would honestly search out a rf-20/magstrike to gut.

Another thought you might want to think about: using a pull pin type tank will vent your reserve bladder so long as the trigger is pulled. You'll inevitably be wasting precious air even with good trigger control. You might want to consider switching to a back pressure style tank (big salvo, hornet, panther) and a "clippard mavo-3" valve (from ebay (clippard.com charges you $10 for shipping + $10 for handling on a $7 valve)). That valve triggers the tank - without venting your reserve. It's the route I went when I made my semi auto dart tag gun. I also sleeved a 1" inner-tube over the rf 20 bladder to increase the pressure to a functional level. Fair warning though - it's a lot of work.

What isn't a lot of work?
Pick up one of these for less than $10:
http://www.amazon.co...r/dp/B002YOXQRY
Marshmallow Mforcers are semi auto/rear loading by design. Once re-turreted to pteg barrels they'll give you ~80' ranges with half the work, and a 15 round turret to boot. Less work, more fire power. One of my favorite go-to primaries. They do look kinda silly - as far as blasters go, but that all changes when you've dropped 2 people during a rush and you still have half a turret full of darts.

Mforcer write up

Edited by shmmee, 10 November 2013 - 05:25 AM.

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#3 Doom

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Posted 10 November 2013 - 09:58 AM

As shmmee suggested, I have experimented with latex tubes on McMaster-Carr for water guns. I wrote a guide about latex tubes for water guns a while back. You might find it to be helpful, Just582. I've done a few things with them for Nerf too.

The nerf bladders use foam latex. I think it has a higher ductility that straight latex (surgical tubing) and therefore more fills. In discussing the materials with Doom (he's spent a lot of time with them in water blasters) I also learned that when an air filled latex bladder ruptures, it 'splodes as loud as a shotgun and might draw unwanted attention. I would honestly search out a rf-20/magstrike to gut.


I don't think the loud noise when bursting has much to do with the material, rather, it has to do with the pressure difference and air expansion. So I doubt the tubes in Nerf blasters avoid this issue. If the Nerf bladders are more ductile then they'll have less of a tendency to burst, which is another way to avoid the issue. Maybe I misunderstand you and that's what you meant?

I think if someone uses a lower pressure tube (like 5234K53 as I suggest in my article) and the tube is covered by a casing that'll prevent most sound from leaving if it bursts, there shouldn't be an issue. I have never had a lower pressure tube burst when not abused. The high pressure tubes seem to want to burst, which makes them particularly bad.
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#4 JPRoth1980

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Posted 10 November 2013 - 10:56 AM

Something I have been considering for way too long is putting a bladder in a Sceptor. The hammer valve only would allow for near-perfect semi-auto and a compressor could keep the bladder topped off.

Basically, a bladder plus compressor plus hammer valve (with a cutoff switched wired around the bladder) would make an effective semi-auto NIC-worthy blaster, to my mind.
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#5 Doom

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Posted 10 November 2013 - 12:24 PM

Something I have been considering for way too long is putting a bladder in a Sceptor. The hammer valve only would allow for near-perfect semi-auto and a compressor could keep the bladder topped off.

Basically, a bladder plus compressor plus hammer valve (with a cutoff switched wired around the bladder) would make an effective semi-auto NIC-worthy blaster, to my mind.


SgNerf did something similar to that for a Magstrike, and it seems to have worked well. A Sceptor would be even better. Give it a try if you have the opportunity.
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#6 C-A 99

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Posted 10 November 2013 - 07:32 PM

I've had a few thoughts on semi/full auto blasters, and on paper, it seems easily possible to put something together that doesn't even require air compressors, HPA, etc., just a good pumping arm.

Ignoring the need for semi-auto, you'd think that rubber tubing able to output a short, constant-pressure air stream would work for an auto-hopper based homemade. After all, this video (that you guys should be familiar with) demonstrates it.

Unfortunately, it seems to need a very loose barrel, but that may not be the case if the air source is from rubber tubing (with sufficient pressure) instead of blowing on it.

After some testing today (with some tubes I took out from a water blaster homemade), and according to McMaster, the tubes hold around 30-35 PSI. (Probably dependent on temperature.) Not exactly sure if this is enough for something high-powered, but it should be manageable to get good performance out of with the right barrel fit/length.

For semi-auto, there's an old valve design that comes to mind. http://www.sscentral...de/testwbl.html It looks great on paper, but is a lot to put together. However, it should be an effective solution, assuming the air tube has enough volume to supply a decent number of shots. (Good pump design will be needed here.)

Anyway, I'm primarily trying to avoid heavy air compressors, expensive HPA tanks, regulators, etc. and uses a rubber bladder for constant air pressure, as well as an easy loading mechanism like the hopper. That said, there's a few principles that still apply even if you're using HPA or an air compressor.

As for the MForcer mod, the lack of constant air pressure for each shot means plenty of pumping after a few shots. With a constant pressure bladder tube, the last shots should be fairly consistent with the first even as the bladder is running out of air and the pressure drops off. I may be thinking this issue is worse than it actually is, but it's still something worth considering.
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