8 replies to this topic

[TantumBull]

Parts from Mcmaster you'll need:
6464K11 - directional control valve (DCV)
5116K81 - fittings for the DCV
(also tubing and barbed fittings)

-this isn't from MM, but you'll also need a hornet valve

Okay, start by putting in the fittings.


Shave out the mav like so.


We're going to be using the catch to operate a small button on the top of the DCV. In stock form, the catch will not fit around the valve. Shave like so. Stock on the left, modded on the right.


The catch is pretty flimsy to begin with, and will bend rather than depressing the button on the DCV. Glue on some thin plastic strips.


And then put on some epoxy putty.


The catch still won't be able to slip over the button without depressing it slightly and making the valve leak air. I shaved little notches in the valve corners on the bottom to remedy this.


You're also going to need to add some plastic to the bottom of the lever on the catch.


All that's left for the trigger set-up is connecting tubing and screwing the valve into the shell. Here's what it should look like.


Let's move to the firing valve. Shave out the front part of where where plunger used to sit so you can comfortably fit the hornet valve in there. Also cut off the front of the plunger. Before gluing the front piece to the hornet valve, do lots of test fitting and sanding to make sure the front orange piece will be seated correctly. When your done, hot glue in the assembly.


Now use the holes in the DCV to screw it in. You'll notice that one screw is upside down. This is to prevent the head from interfering with the catch. This screw is just keeping everything aligned, the left screw is what's actually holding down the valve.


I also ran the screws through the stock priming slider; it covers up the hole and DCV in the back of the gun.


Now we just do tubing and we're done! Drill a hole in the handle as shown. I used 1/4" bit, but than had to widen the hole. If the tubing going through it has a barbed tubing inserted at the hole (my set-up), you'll need a slightly bigger hole. I recommend a 5/16" bit.


Now glue a barbed coupler like so. This line goes to the input.


Now just connect the DCV to the hornet valve and you're done.


Now a lot of you are probably wondering how the hell this works. Doom has an excellent explanation here. Just pretend the 1/4" QEV is a hornet valve. NB: the DCV DOES NOT work with salvo valves. The flow rate is too shitty. I originally intended to use this valve on my DTB (expect a write-up for that *soon*).

What do y'all think?

Oh yeah, vid will be up sometime soon, tonight or tomorrow. This does work though, I've tested.

[FatNerfer]

I like it.

[faddle]

That is awesome. I am going to try that out.

[Zorns Lemma]

Solutions for your shitty flow rate:

1) Get a DCV with higher coefficient of volume (expensive).
2) Put a QEV between the DCV and Hornet tank to dump air from the pilot valve faster.

A cool thing to try for (2) would be to use a smaller nerf tank (SMDTG anyone?) drill a hole in the side for tubing to the salvo tank, and then rig up the DCV to fire the smaller tank which will dump the pilot volume of the larger tank and fire the larger tank.

Hell, you could rig up successively bigger tanks in series doing this for a cool cascade effect.

Edit: yet another thought.
For (1), just adapt one of cheesy's valves. Hornet parts = cheap, 1/2" ID = large airflow.

Edited by Zorn's Lemma, 28 January 2010 - 09:12 PM.

[TantumBull]

I actually tried the series thing with a salvo valve already and neither let air out correctly. I probably need to space them farther apart. For the DTB though I built atmotron's valve out of smdtg pumps.

[Doom]

I'm intrigued TantumBull. I'd definitely be interested in seeing a video of the finished product.

Higher flow rate DCVs can easily be found for cheaper. I and others use Clippard's MJVO-3, which costs $11.94 new from Clippard. The flow coefficient for this is about 5 times higher than Mead one based on the reported data.

I prefer off-the-shelf components as I have no time or patience to make my own, but that might change in the future. Miniature pneumatics are generally not cheap but if you are patient and check eBay periodically you will find deals. Also, the distributor I buy my Clippard components from (N. B. Cochrane) sells them for about 20% cheaper than Clippard does. If you want Clippard valves I suggest calling the local distributor that Clippard suggests.

The tubing and barbed fittings might also be significant bottlenecks. Recently I've put some thought into isolating specific bottlenecks (as opposed to using a "bulk" flow coefficient that describes the entire system) for the purposes of estimating how much of an effect certain design choices might have on performance. Unfortunately, I haven't collected much data so I can't tell you if the tubing and barbed fittings definitely contribute, but you get the idea; this is a real problem worth investigating.

Edited by Doom, 28 January 2010 - 11:38 PM.

[OnyxZenith]

Gah you finished what I've started! > Nice though...

[HOTH]

Genius! Very cool. I love how you adapted the semi-auto part, but I am digging the catch reinforcement as well. Not that it is needed when you keep it as a springer... Damn inverse plungers.

[TantumBull]

Uggh. This gun has just made it's way into the I'm-frustrated-and-don't-want-to-break-you-box. When I hook the gun up to a pump, it functins fine. When I hook it up to an LPA tank, it just leaks air out the valve, unless I pull REALLY fast. Pretty damn dissapontimg after the work I put in this.

It's pretty obvious that the problem is the speed of the button depression. I'm not sure, but I have a hnch that the lever syystem of the catch is giving a "pulley" effect, and pressing the button too slowly. It also definatel doesn't help that I had to increase tension on the trigger to get the turret to rotate properly.

If I ever do get myself to open the damn thing again, I'll probably give it an atomotron valve. This DCV's shitty flow rate and retarded way if cutting off the input are really bugging me (it cuts connection to the lpa taank only when the button is fully depressed).