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Backpack air supply project.

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Backpack air supply project.

Unread postAuthor: Boomer58cal » Wed Jun 04, 2014 7:17 pm

I've been to busy with responsibilities to get much done lately, but my backpack air supply is finally taking shape. It's nothing to fancy. I started with an old Vietnam era frame pack and some 3" sch 40. I have four of the final seven 3"x24" air tanks ready to prep for paint. That's about 3 gal. right now, but should be about 5.2 gal. when completed. A blast shield to give your head and back a layer of protection is in the works. Air is filled through a standard male quick connect with a ball valve and will have both regulated and unregulated attachment points.

This will probably be used with a BBMG and a homemade Über soaker. If anyone has any ideas or suggestions it would be appreciated before I'm complete. Here's what I have so far. The tanks are just sitting on the packs shelf so you can seen what it will look like. There will be three more tanks staggered in a second layer over these. What do you think?
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Re: Backpack air supply project.

Unread postAuthor: jrrdw » Thu Jun 05, 2014 6:51 am

As long as you keep the manifold protected you'll be golden.
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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Thu Jun 05, 2014 4:20 pm

First test... was a flop. :cry: The regulator greatly restricts the flow, so there's not enough agitation of the BB's to feed reliably. Test at 95 psi.

I am removing the regulator post haste and will add a video of it unregulated later today or tomorrow.
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Re: Backpack air supply project.

Unread postAuthor: jrrdw » Thu Jun 05, 2014 7:00 pm

Is this a cloud configuration or do you have a vortex block built into it? Yea it's easy to hear when you lose the feed, other wise it spits them right out. Sounds like you have good power when you have the feed going. Are you sure it's the regulator causing the feed loss?
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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Thu Jun 05, 2014 9:19 pm

Its a cloud. Here's the gun unregulated. About 50 rounds for a second.

Once I get everything working I plan on building one with a vortex block, I just haven't had a chance.

Here's another spare parts prototype. A .177 cloud I've been playing with. Well it's rate of fire is astonishingly quick compared to my 6mm airsoft cloud, the magazine/chamber is far too small. It runs out of ammo after only two or three one second bursts. Another flaw in this design is that the BB's roll out of the barrel very easily due to the small diameter of the chamber. I guess it's time for me to start playing with detents.
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Re: Backpack air supply project.

Unread postAuthor: jackssmirkingrevenge » Wed Jun 11, 2014 7:27 am

Why not a regulated paintball tank setup? Not too expensive, much more compact. Large volume low pressure tanks do not make too much sense.
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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Wed Jun 11, 2014 5:04 pm

jackssmirkingrevenge wrote:Why not a regulated paintball tank setup? Not too expensive, much more compact. Large volume low pressure tanks do not make too much sense.

I'm also using the pack to power a Über Soaker. I have kids and summer is coming fast.

I have 4 low pressure compressors ranging from 3 gal. to 65 gal. So high volume low pressure is convenient right now. I have 2, I think they're 300 gallon, air tanks I'm going to add to my 65 gal. compressor. This will give me an almost unlimited 120 psi air source.

I do have 6 small O2 tanks I'm planning on using at some point, but I haven't had time to find a regulator for them. They are 3000 psi bottles, but they are only about the size of a 1L soda bottle.

The pack is right about 5.2 gal. and I'm getting about 15 sec. @100 psi before I run out of ammo, with about 80 psi left in the tank. I'm going to increase the size of my chamber to hold about 50% more ammo, hopefully find a larger regulator and push the pressure up to 120 psi. I think that will get me maybe 20-25 sec. or about ten 2 sec. bursts when regulated at around 80 psi.

The pack weighs maybe 15 or 20 lbs( if that ), so it feels light on your back. No where near the weight you would have on this pack if you were backpacking.
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Re: Backpack air supply project.

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Re: Backpack air supply project.

Unread postAuthor: Lockednloaded » Thu Jun 12, 2014 12:00 am

If you're having issues with low-flow from the regulator, why don't you put a small accumulation tank between the regulator and the gun?
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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Thu Jun 12, 2014 10:36 am

Lockednloaded wrote:If you're having issues with low-flow from the regulator, why don't you put a small accumulation tank between the regulator and the gun?

Not a bad idea, I don't know why I didn't think of that. I do the same thing on my 66 Volkswagen to the fuel line. The dual Weber carbs suck so much fuel the small stock fuel line won't keep up, so I have a small reservoir where is the fuel lines spilt to the dual carbs. This keeps the float bowls full during full throttle conditions. It would do the same thing here.

I have several 1' long pieces of 3" sch 40, I could use one as an accumulator. That would at least help for short bursts. I will try it, thanks.

Almost finished. Hopefully I'll get to it this week.
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Re: Backpack air supply project.

Unread postAuthor: Solar » Thu Jun 12, 2014 4:40 pm

Palmer's Pursuit has the fittings and regulators you need. www.palmer-pursuit.com
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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Thu Jun 12, 2014 6:22 pm

8)
Solar wrote:Palmer's Pursuit has the fittings and regulators you need. http://www.palmer-pursuit.com

Thanks for the link.

I did not see a regulator for my o2 tanks at Palmers, but maybe I'm looking for the wrong one. I'll try to remember and take a photo of my bottles when I get out to my shop this weekend.

Paint ball tanks seem pretty cheap, I might try those out.

I weighed the pack. It comes in right at 20 lbs. The frame pack makes it feel pretty light though.

Edit...
I found this backpack design on YouTube. Well the layout could use some work, the concepts pretty neat. The ammo and vortex block are located in the backpack and the ammo feeds through a hose to the barrel of a gun.
[youtube] https://www.youtube.com/watch?v=n2-flxp ... ata_player [/youtube]

First pressure test of my complete pack was successful. I pressurized it to 100 psi for one hour, it lost only 1 or 2 psi. I think that's about as good as I can ask for. I doubt I would ever leave it pressurized for that long in actual use, but I wanted to be safe.
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It's volume is right at 1200 ci.

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Re: Backpack air supply project.

Unread postAuthor: Boomer58cal » Tue Jun 17, 2014 6:58 pm



Here's the first full test of the complete pack. The supply of air lasts a long time. The big problem is once the ammo supply is about 1/2 or 2/3 empty I start to get feeding problems. I only get about 10 sec. of reliable feedng. In an attempt to fix the problem I have build a larger chamber for the gun. The new chamber is about the same length as the old chamber only 2" dia instead of 1.5" and holds 400 more rds, bringing the total to about 1000 rds. I will test it tomorrow.

Once I get the bugs worked out I think I can get 20-30 sec. of continuous fire. Then a vortex block may be in order. My larger air compressor is at my property in the woods( the place we play airsoft ), I will test the pack to 120 psi when I get out there. I think feeding will improve at higher pressure. Should be impressive.

Well, what do you think.

Edit... Video with new chamber.
I loaded about 1000 BB's in the chamber, but next time I will try about 1100 because I ran out. I was able to manage about 25 sec. of continuous fire that time. The rate of fire drops fast after about 15 sec. so I may try a 3/8's regulator to even out the pressure curve at maybe 80 psi. Can't wait to test a little higher pressure.
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