15 replies to this topic

[CROW]

Hey all. I'm currently doing some research into how to build a specific design, and I thought I'd start it here to get some feedback from people who have more experience with this kind of stuff than I do. To keep this short and sweet, I'm looking to create an air-pressure system that could fire multiple, consistent shots off of one fill of the tank. My only constraints are that the tank would need for be fill-able from a hand pump (a high-efficiency dual action pump?) and that the tank NOT take a crazy amount of work to fill to ideal pressure. This will be used in wars, and it needs to be practical.

Other thoughts: I'm obviously not looking for hundreds of shots off of a manually pressurized tank, maybe 3-4 to be realistic. I'm thinking that the tank for this system would need to be something stronger than PVC, such as aluminum, to be able to work at higher pressures. Could a solenoid system rigged to the trigger work?

Anyways, this is what I'm looking into. If you have any experience that could start my research and planning off in the right direction, it would be much appreciated. If not, still, thanks for your time

[shmmee]

You're already kicking around some of the good questions to start asking.
Here's my resume:



^click that. it's a firing vid.

It's a Dart tag gun with a big salvo tank (back pressure tanks are key) Banded RF20 bladder and a Clippard "Mavo-3" valve(get it from ebay not clippard. Clippard reams you on shipping).

My lessons learned:

Pick a blaster with a turret that actuates by the trigger pull. (firefly, maverick, dart tag gun - my personal favorite)
For Consistent pressure I would suggest a banded bladder (stretch two layers of 1 1/2" bike inner-tube over it). It spares you the cost of a regulator.

Use a back pressure tank. Big salvo, panther, hornet and a Clippard Mavo-3 valve. That valve shuts off the air reserve then vents/fires the tank. If you go with a pin pull tank instead you are venting excess reserve out the barrel with each shot.

My system gets me ten shots @ 70'.

[rego]

A quick exhaust valve and 3 way directional control valve would fit the bill. Doom had a thread about using one a while back, and they are extremely efficient. Simply attach the output of the 3 way valve to the input of the qev, then add whatever size firing tank you would like to the quick exhaust valve cylinder port. Both can be sourced for between ten to twenty dollars. An air cylinder could then be used to cycle a breach, or you could straight up use a hopper on the qev's output. A bladder would keep a constant pressure for each shot keeping it consistent in range and power. The hardest part is finding or making a good shell to put it in.

Edit: Essentially, the post directly above mine is the same thing, just actually made.

Edited by rego, 25 June 2013 - 05:18 PM.

[CROW]

I'm really excited to see these two posts, this gives me a great starting point. Thanks shmmee and rego for that, much appreciated.

A quick question - just because I'm not a fan of the bladder style tanks, do you think it would be possible use a rigid back pressure tank such as aluminum with a regulator attached? Or do you think it would be inefficient due to a long priming (or pumping) time and a low amount of cycles (shots fired)? If hand-pumping a rigid tank wouldn't work, I may have to consider using an air source such as a HPA tank.

[roboman]

I'm really excited to see these two posts, this gives me a great starting point. Thanks shmmee and rego for that, much appreciated.

A quick question - just because I'm not a fan of the bladder style tanks, do you think it would be possible use a rigid back pressure tank such as aluminum with a regulator attached? Or do you think it would be inefficient due to a long priming (or pumping) time and a low amount of cycles (shots fired)? If hand-pumping a rigid tank wouldn't work, I may have to consider using an air source such as a HPA tank.

These are awesome, and really cheap. They've got them in 3 sizes. They should work well for your purposes.

[shmmee]

You could go that route, just add a regulator to keep pressures consistant, and please - use a fittings tank intended for air pressure. I wince whenever I see a homemade diy PVC tank.

[Draconis]

The advantage of the bladder tank is that the final couple of shots still get close to the same range as the first. This is not the case with regular hard tanks.

[CROW]

Roboman: Those look great! I assume those are metal, finished with some sort of white spray?

Shmmee: Of course, I'm building this for longevity as well as not-kill-people-with-plastic-shard'ity, hah In experimenting with the gun you showed me, did you ever try the hand tank/regulator combo? I'm curious what the pumps to shot ratio was.

Draconis: The regulator should prevent the inconsistency, more or less, I thought?


Once again, thanks for everyone that has put in their input, its been great!

[shmmee]

... did you ever try the hand tank/regulator combo? ...

Nope. I went straight to a bladder. I've never counted pump strokes, but I'm sure it will vary between tanks, reserves and pumps. I counted about 30 pumps in my vid which will normally get all 10 shots off - so 3 pumps per shot? At the very least a dual stage pump is a necessity.

Edited by shmmee, 25 June 2013 - 09:56 PM.

[roboman]

Roboman: Those look great! I assume those are metal, finished with some sort of white spray?

Shmmee: Of course, I'm building this for longevity as well as not-kill-people-with-plastic-shard'ity, hah In experimenting with the gun you showed me, did you ever try the hand tank/regulator combo? I'm curious what the pumps to shot ratio was.

Draconis: The regulator should prevent the inconsistency, more or less, I thought?


Once again, thanks for everyone that has put in their input, its been great!

They are polypropylene. Rated to 500 psi burst, 120 working. If you could somehow get one to fail, it would just tear, and would not send shrapnel anywhere. Super lightweight, too.

[ShaNayNay]

I've got a similar project lined up for this Winter. It is possible to create your own semi-auto valve from a hornet trigger system as done here.

I'm planning to do a backpressure tank variant of this design inside a Firefly. I suggest using a Firefly shell over a DTB due to more comfort and a significant more amount of workspace. I've discussed all of this with Schmmee in the past and he is definitely the one to consult on this type of project.

Good luck.

Edited by ShaNayNay, 25 June 2013 - 11:04 PM.

[CROW]

Roboman: Sweet, I will definitely keep that in mind when I go to build this. Once again, thanks for the reference!

ShaNayNay: I'm actually going to use the Supertech 9000 shell I finally got a hold of! I looked a lot more into the thread that rego referenced, by Doom, and I'm leaning toward going that way. Doom used a combination of a QEV, a three-way directional valve and a pneumatic cylinder to cycle the bolt. It took me a little while to understand, but now that I've got it, I really like the set up. That being said, using the Hornet trigger system looks to be a lot easier to build and work with. Wish you the best mate!

[shmmee]

I spent several weeks trying to get a hornet trigger system to work - it would never seal. I even re-built the manifold in soldered brass tubing and drilling it out of a soft plastic block I found but the o-rings kept letting air by in all 3 materials. I would definately go with either the mavo-3 valve or the Doom set up. Doom is a 'friggin genious and I've always been an admirer of his work.

[azrael]

Here's a useful thread for you:
http://nerfhaven.com...showtopic=21429
The second post is what I think you'd find interesting.

[spencerak]

This may help alot: http://nerfhaven.com...showtopic=21480 Basically a semi-auto big Solvo tank

[Hipponater]

The advantage of the bladder tank is that the final couple of shots still get close to the same range as the first. This is not the case with regular hard tanks.

Draconis: The regulator should prevent the inconsistency, more or less, I thought?

The regulator will only make the first few shots consistent. As soon as your tank pressure drops below the regulated pressure, you're going to have weak shots. The advantage of having a bladder is that you have variable volume but more consistent pressure. Rigid tanks are the opposite, rigid volume but variable pressure. Our blasters are pressure driven, so a bladder would be better in my opinion.

With a rigid tank, you're going to need to pressurize it much higher than you would with a bladder, in order to get the same number of shots. This high over pressure is going to require a regulator to make the first few shots consistent. With a bladder, you can adjust pressure somewhat by banding it, but you don't need a regulator because the pressure will be much lower.

I have a magstrike bladder hooked up to an AT2K tank through the magstrike valve (not totally sure what it's called). I can pressurize the bladder, then press the magstrike valve which fills the tank. Then fire, and press the magstrike valve again which refills it. Fairly basic, but I'm sure you can rig something up with a back pressure tank or other pieces so you're not pressing a button after firin