30 replies to this topic

[CaptainSlug]

Working on this one kind of slowly at the moment. The goal is to have 6 semi-automatic shots available whenever the 75ci tank is primed.

It's very similar to the QEV blaster that Doom made. The high pressure tank is down-regulated to between 15psi and 30psi to fill the low pressure tank. The Quick-Exhaust valve is piloted and refilled by a 3-way solenoid directional control valve.

Only differences are
1. I wanted to keep all of the pneumatic components metal and pressure-rated
2. 3-way control valve is a 12v solenoid valve
3. Solenoid valve is powered by a 12v battery (AA x 8 battery box)
4. Solenoid circuit is triggered by a push-button switch mounted in a joystick grip
5. Includes a hand-operated pump for recharging high pressure tank, with a stem valve as a quick refill option

I'm also making the 7ci low-pressure tank a modular item so that it can switched out for a higher volume if I would like to be able to fire arrows or foam balls.

Edited by CaptainSlug, 02 March 2011 - 05:48 PM.

[Talio]

Do you keep a lawyer on retainer for when the FBI finally seizes one of these things and you get arrested? Cause in my head the person who made that thing has to have a contigency for every possible thing that could happen to him. I would love to hear your zombie survival plan. Somehow I think you have blue prints.

All joking aside, that thing is really cool.

[CaptainSlug]

Some revisions based on how the hardware/fittings are going together.

Edited by CaptainSlug, 12 February 2011 - 01:50 PM.

[CaptainSlug]

It's built and it works. I need to do some fine tuning. I also need to get a better regulator because the one I have been using is proving to be a significant bottleneck in flow rate between the high-pressure and low-pressure tanks.


The RF20 pump isn't very good, but one 40psi fill will net me 9 semi-auto shots.
I will post with more photos and specifics soon.

Edited by CaptainSlug, 02 March 2011 - 05:41 PM.

[CaptainSlug]

Here's how it works at the moment.

1. The high pressure tank is down-regulated to the firing pressure. Which is supplied to the low-pressure tank through a 3-way valve that's setup for Normally-Open.
2. The low-pressure supply pilots the Quick-Exhaust-Valve through the Inlet port sealing off the Barrel, which is connected to the Exhaust port on the QEV.
3. The low-pressure tank is connected to the Cylinder port of the QEV.
4. The low-pressure supply is also connected to a 2-way Normally-Closed valve.

Once the two solenoid valves are energized the 3-way valve cuts off the low-pressure supply. At the same time the Inlet port is vented of back-pressure through the 2-way valve.
The venting of back-pressure causes the low-pressure tank to fire the dart from the barrel.

The 3-way valve also vents the back-pressure from the QEV, but has too low of a flow rate to quickly pilot the Quick-Exhaust-Valve. If I had one with a much higher flow rate is could perform both tasks.

I got to practice aluminum welding while making the frame that all of the parts mount to. The yellow-top part is the 3-way valve.
The blue-labeled part is a 2-way solenoid valve meant for controlling air horns. A wing-nut holds the 8 x AA battery box in its hinged bracket.

The high-pressure tank is actually a throwaway propane tank. The 1/4 NPT adapter for it is screwed into a tee that I added a couple extra 10-32 UNF ports to.
An optional tire stem valve is included for refilling from a compressor or a more effective bike pump.

Edited by CaptainSlug, 02 March 2011 - 09:55 PM.

[Split]

I used that particular valve as an engineering project last semester, determining the factors that affected the work transfer efficiency and optimizing the system (that's what the HPA rig I sold was for). 7 cu in is a good size tank, so nice choice with that, but the elbow to the valve and the geometry of the tank are inhibiting your airflow. You could probably get a good 10% more energy going into the hopper by turning the QEV 90* and having a more pancake-shaped tank feeding directly into it.

Other than that, it looks pretty good, as always. Jlego guessed, and I agreed, that this was moved from your sekret forumz?
How many shots are you getting from each fill? What's the parts cost on this thing?

[TantumBull]

That looks pretty sweet! Do you have any problems with the RF20 pump wobbling around or is its attachment at the rear enough to hold it steady?

[CaptainSlug]

Split, on Mar 2 2011, 11:11 PM, said:

1. You could probably get a good 10% more energy going into the hopper by turning the QEV 90* and having a more pancake-shaped tank feeding directly into it.
2. that this was moved from your sekret forumz?
3. How many shots are you getting from each fill?
4. What's the parts cost on this thing?

1. Interesting. The tank shown is a leftover part from work.
2. Yes.
3. At 40 psi unregulated I'm getting 8-10 shots. Once I get a better regulator and a better pump that number will improve.
4. I'll make a part list an cost estimate once I have the parts finalized. But it's not a cheap project. I haven't tracked costs closely, and a fair number of the fittings I took from the leftovers bin at work.
I'd guesstimate $175.

TantumBull, on Mar 2 2011, 11:28 PM, said:

That looks pretty sweet! Do you have any problems with the RF20 pump wobbling around or is its attachment at the rear enough to hold it steady?

It needs a frame piece at the front if I wanted to use it for anything other than testing. Mounting it from only one end allows it to flex too much.
I have yet to add a tank cover too.

Two of several things still on the to-do list.

Edited by CaptainSlug, 02 March 2011 - 10:31 PM.

[bennorco]

It would be cool to see a video!

[WicketTheModder619]

That looks awesome slug! I wonder how many more shots it would produce with a small basketball pump. And how many pumps it would take. Great work again, your work never ceases to amaze me.

[utahnerf]

What sekret forumz?!?! Also, how heavy is that thing? it looks unwieldy.

[Daniel Beaver]

Neat. Semi-auto is the way to go for airguns, since pumping between shots is lame. In some ways, I like this better than your old stuff, since the design is more sane

*goes back to work on my PVC homemades*

Could you set it next to another blaster so we can get a sense of scale?

Edited by Daniel Beaver, 03 March 2011 - 11:38 AM.

[taerKitty]

You call this sane? Then again, we're talking Nerf, which has a rather elastic definition of sanity...

Back to the mod - fantastic (as usual). How much do the parts cost, and where would someone buy them?

[Inferno Falcon]

Mind blowing as always. I'm also interested how many rf20 pumps it takes to get the tank to a usable pressure.

Edited by Inferno Falcon, 03 March 2011 - 02:13 PM.

[Draconis]

Slug, don't tell them what kind of tank that high pressure unit is. We don't need anyone hurting themselves trying to modify one for use. Otherwise, that looks pretty awesome.

[pjotrkuh]

So in fact it is almost a PB marker... only this one can be pressurized in the field, kudo's for that

Is it possible to use a manual operated valve instead of the solenoid?

[blitz]

Looks like a homemade SGSL. Very cool. But is this in any way war-usable?

[Exo]

Not to sound like the power-obsessed, gun-slinging, psychotic, angsty teenager I am, but what's the range?
Do the electric valves let out a certain anount of air, or do they stay open all the time?
Looks cool, I can't wait to see it with the shell on it. Also can't wait to compare it to the Archangel that was just made, similar concepts and such.

[CaptainSlug]

To-Do List
1. Better regulator
2. Better pump
3. Tank surround
4. Add ball-valve to dart hopper
5. Muzzle brake

bennorco, on Mar 2 2011, 11:34 PM, said:

It would be cool to see a video!

I will get around to that eventually.

utahnerf, on Mar 3 2011, 10:27 AM, said:

What sekret forumz?!?! Also, how heavy is that thing? it looks unwieldy.

4 or 5 pounds.
It's heavy. But what do you expect from an all metal monstrosity.

Daniel Beaver, on Mar 3 2011, 12:34 PM, said:

Could you set it next to another blaster so we can get a sense of scale?

taerKitty, on Mar 3 2011, 01:33 PM, said:

How much do the parts cost, and where would someone buy them?

I got the solenoid valves through eBay. The battery box and push-button switch from RadioShack. The joystick from my parts box. And the rest of the parts through Mcmaster.

pjotrkuh, on Mar 3 2011, 05:34 PM, said:

Is it possible to use a manual operated valve instead of the solenoid?

It would have to have a high flow rate in order to pilot the QEV quickly. Which would mean it will probably be expensive, or large, maybe both.

blitz, on Mar 3 2011, 06:23 PM, said:

But is this in any way war-usable?

Practical? Not particularly.
Safe? Only if the firing pressure is within a safe range.
Fun? Hell yeah.

Exo, on Mar 3 2011, 06:39 PM, said:

1. what's the range?
2. Do the electric valves let out a certain anount of air, or do they stay open all the time?
3. Looks cool, I can't wait to see it with the shell on it.

1. Depends on the firing pressure.
2. They only pilot the QEV, so their vented output is consistent, as is the firing volume of the QEV and Low-Pressure tank.
3. I'm making a shell? I'm only going to be adding a piece to support the pump, and surround the high-pressure tank a little.

Edited by CaptainSlug, 03 March 2011 - 06:03 PM.

[ricochet]

Great build slug. The joystick setup is an interesting idea, I like it. When you get around to getting the new regulator, I'd love to hear where you get it and which one it is (ie. mcmaster part # if you buy from mcmaster). I have been needing a regulator, but am still new to them, how they are installed, and which to buy. Keep up the good work.

[taerKitty]

Did you say "muzzle brake"? Good lord, does this thing have an actual recoil? The more I hear of it, the more I love it.

[PVC Arsenal 17]

@Draconis: Modify? It's just a matter of threading on one of these adapters and possibly removing the valve core from the propane bottle to improve flow. No big deal really. In fact I made this same suggestion to Doom some time ago as an alternative to his Catalina cylinder.



CaptainSlug: "It would have to have a high flow rate in order to pilot the QEV quickly. Which would mean it will probably be expensive, or large, maybe both."


I disagree. The MJVO-3 should be adequate by itself, and if not, you can make a QEV cascade using the MJVO-3 to pilot a small [inline] QEV which the pilots the larger one. It would cost less than the Mouse valve, take up about the same space, and eliminate the batteries as well the weight associated with them.

Edited by PVC Arsenal 17, 03 March 2011 - 08:27 PM.

[CaptainSlug]

Yes, the only downsides to using throwaway propane cylinders are
1. You have to empty them using a camp stove, then finish it by venting it outside for quite a long time. Make sure to tie or weigh it down with something, then depress the valve stem using the tank fitting adapter to vent it out. DO NOT HOLD THE TANK WHILE DOING THIS, it will get cold enough to freeze your skin to it because the propane is undergoing a phase change from liquid to gas. Also obviously do it away from a flame source.
2. Even after being emptied they smell.

Obviously the process is dangerous.

taerKitty, on Mar 3 2011, 08:45 PM, said:

Did you say "muzzle brake"? Good lord, does this thing have an actual recoil? The more I hear of it, the more I love it.

No, it will be a cosmetic part painted a fluorescent color for safety reasons.

PVC Arsenal 17, on Mar 3 2011, 09:17 PM, said:

The MJVO-3 should be adequate by itself

Yes, rated for 25 scfm @ 100 psi the Clippard MJVO-3 or MJV-3 should be able to pilot a QEV fairly well.
I'm not sure where the floor on SCFM is for piloting this QEV, but I suspect that anything below 15scfm @ 100psi is not likely to work very well. Getting it filled and sealed is much easier than exhausting it. That can be done with a valve rated as low as 1 scfm @ 100psi.

I'm going to order a surplus MJV-3 to test it out. I have a tiny QEV in my parts bin if I need to try that as well.

Edited by CaptainSlug, 05 March 2011 - 08:15 AM.

[Doom]

Great work.

I've thought of doing a QEV + hopper since last year, but I've been way too busy to get around to it. It's not that hard of an idea to think of, as Split did the same thing last year as I recall. (Edit: Just to be clear, I'm no credit-whore, and I don't know who thought of combining a QEV and hopper first. My point is more against all of the credit-whores here. This is just the logical progression of new technologies, not anything worth going nuts over as some people do.)

MJVO-3 is great to pilot the QEV used here. I highly suggest it and its variants.

It seems I might have to actually make something for once now with all of these recent air gun projects. If I only had the free time...

Edited by Doom, 09 March 2011 - 11:02 AM.

[BritNerfMogul]

This is bat-shit insane. It's perfect.

Shame you couldn't keep it the same colour as the plans. That would have been awesome.