The Evil Twin

[DocsMachine]

Doc I sent you a pm..... There things to discuss

-No got. Did notice a couple other overdue PMs I need to get to... Sorry, folks, I guess I don't check those as often as I should.

Doc - use all of your powers to make a single center feed over under work correctly. Make some ridiculous ass detents or something. DOOO ITTT

-Been pondering it, but there's no easy or obvious mechanism. As ECAP's drawing shows, there's just too wide a separation between the barrels. Even dropping it to a pair of, say, Pro-Lite or Phantom barrels would still make the step to wide. The fast fix is to widen them to the point there's a whole ball in between, and I think that would have problems all it's own.

Apart from that, we'd have to have, like, sliding feed gates or something, and without some pretty good timing, given that half a ball can fall through, that would basically become a guillotine.

.331...... Basically a half a ball bore gap

-Close, though the dimensions are off a bit. The bolt bores are .6875", or 11/16", and while I'd planned on a little separation between the barrels (the Vee-Twin uses 1/16" or .0625" ) I had a brain-fart while drilling, and made the separation exactly 1". No big, this was always intended on being just a prototype/proof-of-concept, and virtually no barrels out there measure a true 1".

But that just means the actual 'step' between bores is...0.3125. You were off by a whole eighteen and a half thousandths!

We'd have to separate the barrels by nominally 3/8", or .375", to get a nominal-one-ball space in between. Not impossible, and wouldn't make the thing all that much larger, but I suspect would cause feed issues all it's own.

In any case, running something like this on a single hopper just runs out out of paint twice as fast. It'd be nice from a weight and volume issue, but I'm not sure it's possible.

What about a pair of right-feeds, stacked on top of eachother, connected to a single vertical "stack".

-The two most likely possibilities is either it would constantly jam, or only the bottom barrel would get fed. It might be possible to offset the feed just above the first 'leg', so that paint is encouraged to fall either way.

I suspect what you'd get, though, is one barrel would feed reliably, and the other would "skip" a lot. And keep in mind, that on a single-valve/double-barrel like this, if one barrel is empty, you tend to get a considerably lower velocity out of the other. (Because the air burst finds it easier to go out the barrel without an obstruction.)

For the time being, this one's getting standard left and right feeds, since we know those will work. We can try other options on later builds.

Doc.

[BrickHaus]

Beautiful work Doc!

[lhamilton1807]

I’ve gotta sub this. I’m amazed at what you’re creating out of just a block of aluminum. Where’s my popcorn?

[DocsMachine]

It is my sad duty to inform you that, at least this specific gun may have a fatal flaw.

I've been worried about the ball detent placement for the upper barrel, and as I was turning it over in my head while I was working on other stuff, another issue came to mind.

And since I have a touch of ADHD, I had to check it out. And THAT involved making some fixtures that I'd already been planning, but hadn't scheduled to actually build 'til this weekend.

So after several hours or fiddling and fumbling, I had the fixtures made (not 100% happy with 'em, but they work) and had fitted the upper barrel feed tube. So far so good.

But re-setting the fixtures for the lower barrel, immediately revealed that yes, the detent placement cannot work, and yes, the other bit I'd thought of, will also be a significant issue.

To wit; the lower feed tube interferes with the upper bolt tube.



You can see where I plugged the upper-tube detent hole- the lower feed slices right through the center of it.

And, right below that, you can see where the opening also slices into the upper breech area. And not by just a little, either.



Now, tomorrow or this weekend, after the Loctite has had a chance to fully cure (and I've gotten some of this other work off the tables, and maybe had a chance to clean the shop a bit ) I'll re-bore both those passages and see what our results are.

At best, that portion of the feed tube is going to be paper thin, at worst it'll just be a somewhat smaller hole with paper-thin edges. We should still be able to function-test this gun, but this design, as it sits, is not what you'd call marketable.

Now, how fatal is all this? As Miracle Max might say, it's not all the way dead, yet.

The detent is going to be tricky, and will probably wind up having to be an Evo/F4 style wire nubbin, up by the sight rail. I may also be able to fit the same Spyder/Intimidator rubber nubbin like I use on the Automag adapters. On that one I may be able to fit a cover that basically conceals it.

I'll ponder that one some more.

The feed tube issue? The only fix is to separate the barrels some more. I'd meant to have the same sixteenth-inch as the Vee-twins on this one, but my hands got ahead of my brain and I made them at exactly 1.000" separation.

If we raised the upper barrel by a hundred thou (0.100") or even an eighth (0.125") I think the feed neck might still just barely break through, but the bolt bore won't break through the tube itself.

So, a solid setback, yes- although not any kind of an issue on the Vee-Twins, that's an already-proven design. But I think I can still make this gun at least functional, if maybe not ready to fully finish and field.

Stand by, we ain't done yet!

Doc.

[Ecapnation]

Do a skip swift style detent....

Down vertically through the sight rail.

I can grab you a photo he used off the shelf spring plungers but I'm betting you can hide a Timmy style

[Meleager7]

....or an upside down tippmann detent?

[Paintslinger16]

Could you center feed the top barrel and side feed the bottom barrel further back? I realize that would need a shorter bolt.

[BrickHaus]

For the feed tubes. What if you have the bottom feed tube hole bored almost 90* off level, then 45 out after you clear the body? The top feed neck could stay the same and it may look a bit odd, in the fact that the left hopper would hang further off of the gun unless you put a radius pulling back. but that should solve the issue no? You have the extra height to work with.

Im thinking a ULE warp angle on the bottom with something added on.

[DocsMachine]

[Do a skip swift style detent....

-Never saw one of those off the gun. If you've got a pic of the piece he used, I'd be interested to see it.

On the same note, I was thinking of a delrin detent nose and spring, kind of like the '03 Shockers and a few others used, but also up in the sight rail.

....or an upside down tippmann detent?

-That's... actually a pretty good idea. I tend to prefer spring-loaded detents rather than rubber/urethane, when the gun's a closed bolt or is stored with the bolt closed for long periods, as no matter how good the rubber, at some point it "takes a set". But a quick slot and a spare strap/cover from a ProLite sure would be easy.

What if you have the bottom feed tube hole bored almost 90* off level, then 45 out after you clear the body?

-I wasn't thinking this bore-interference at the time, but I was thinking of having a removable feed neck, if I couldn't get a good press fit at that angle.

Yeah, a passage through the body at a lower angle- 30° would probably do it- with an add-on external neck'd do it.

Doc.

[Ecapnation]

I'll grab you a photo tomorrow

[Cunha]

Man what a thread!

[Trbo323]

It wouldn't be easy..... Here's what your up against.
.331...... Basically a half a ball bore gap

Kpsc does it with the pacemaker

This is also assuming you want balls 1 and 2 in the stack to be the chambered balls.

If you use balls 1 and 3 you have a lot more room to play with

Sent from my motorola edge 5G UW (2021) using Tapatalk

[Ecapnation]

I've never seen one in person they are all sitting on walls lol

[JeeperCreeper]

I guess the real question here is have you over engineered a double barrel swab yet?

[gabe]

Fantastic work so far! Too bad the feed tube interferes there.

One solution would be to lay the feednecks down past 45 degrees. You can use a Sconi lean elbow which tilts the hopper inwards on a normal 45 degree elbow to make up for the lower angled feedneck.

Another option would be a bolt on feed tube on at least one or both sides like the PTP autocockers but moreso like a vertical powerfeed tube. Basically a vertical feed tube screwed into the side of the body with a powerfeed sort of plug at the bottom to assist routing the ball laterally into chamber. Pretty much a power feed tube but vertical on the side of the body.

[flyweightnate]

This is what I came here to suggest. A vertical stack with a parabolic plug to roll it in the side.

[DocsMachine]

Extra big post! Grab a drink and a sandwich and buckle up, we've got a couple days to cover.

After the mockup, it was time for some feed necks! But first, I wanted to sand things a little smoother while the sides were still flat and clear. I used the same clamping fixture to hold the backblock in place, so everything could be sanded together.



For a proper client job, I'd have done a lot more work, eventually getting the thing ready for polish, but this is just a prototype and I was eager to get it together and see if it actually worked.



I located and drilled both upper and lower detent holes, which as most of you already know, was at least 50% mistake.



I then took a couple hours to make up these fixtures, to hold the body securely at 45 degrees. Both for boring the feed ports, and holding the body while the necks are pushed in on the press.



I then carefully located, drilled and bored the upper feed tube, putting the higher one on the right, to hopefully help a typical right-handed shooter to sight down the left side of the gun.



(The notch on the fixture was intentional, or at least I knew it was going to happen.)

I measured the resulting bore, whipped up a feed tube to match it with approximately two thou of interference, hauled the whole mess over to the big press, smeared everything liberally with red LocTite, and shoved 'er in place.



Now, as we already know, there was a bit of an issue with the other side. Again, still just a prototype, so to save the build, I spun up a tight-fitting plug, and Loctited that in to fill the as-it-turns-out-unusable detent hole.



After the red goop had cured a bit, I sawed off the bar and milled, then lightly filed the rest flat.



Then located, drilled and bored the lower feed tube, confirming another worry- that the feed tube would, in fact, interfere with the upper bolt tube.



But, I went ahead and slapped in the other feed tube anyway.



Now, the bores always need to be reamed out after pressing in a feed neck, but this one was just a bit more cluttered than usual.



To be continued!

Doc.

[DocsMachine]

After the Loctite had cured overnight (it doesn't take that long, but I needed my beauty sleep ) I set it back up in the vertical vise, and used the coaxial indicator to get a perfect "zero" on the bore.



I bored and reamed them both out, leaving them clean and smooth... but also, as I feared, leaving a slight hole in the lower feed tube, through to the upper bolt tube.



(Which I apparently didn't get a pic of. ) As noted earlier, that can likely be solved entirely simply by separating the upper and lower barrels- I suspect just 80 to 100 thou would do it. (0.080" to 0.100")

The other issue as giving the upper tube back a detent, as the conventional side-mounted one could not be used. After a bit of pondering, I milled this wee little feature just above the feed neck and just below the sight rail:



I then took only two tries to make a standard spring-detent plug out of a scrap of white Delrin...



... Which I miraculously managed to NOT lose a dozen times, and then making a matching aluminum cover, which all goes together like so:



It is effectively at the same orientation to the feed tube, as a conventional 'Cocker detent is to a standard center-feed.



A quick check, and looks like it'll work fine!



A quick scrub with hot water and dish soap, and lo and behold, Ladies and Gentlemen. It's basically DONE.







The last thing before we can actually try it, is we still need bolts. Two chunks of black Delrin, a few minutes on the lathe...



A little gussying up...



And not wanting to waste time fitting them with detents for proper pull-pins just yet, I just grabbed a couple of old-style push pins out of the parts boxes, and voila!



And there she is, Ladies and Gentlemen! One complete, functional Evil Twin Autococker!



Did I say functional? Yes, I did. I have actually fired paint from this badboy!

Now, that said, she's not yet ready for prime time. My compressed air tanks are all but empty, so the only thing I had was a cold 20-lb CO2 tank, from which I could barely get 500 PSI, straight. I also had to go through three 3-ways before I found one that wouldn't leak, and that third one is giving me timing issues.

On the plus side, the block cycles easily, smoothly and quickly. It shows none of the potential binding issues I'd been worried about.

On the bad side, there's a huge difference in velocity between the barrels. Like almost-normal out of the top, and less than a third normal out of the bottom.

The bottom bolt is bored through, and what's clearly happening is the air burst is blowing right through without 'diverting' through that bolt to the ball. So what I'll need to do is probably add a restriction or restrictor of some kind in the top bolt, probably adjustable.

But first, I need to sit down and get this thing properly timed, and top up on compressed air so I can feed this thing the pressures it's likely going to want.

BUT... it's cycled and fired. And got me cackling like a supervillain.

Stand by for more!
Doc.

[Big Phil]

OMG Its amazing

[Meleager7]

We need a shooting video !!!

[BlindFaith429]

Man, thats awesome. Can't wait to see this running.

Now slap on an Eblade and let loose a pair of ropes

Edit: If you look at the pic of the detent in the bore, you can see the hole made in the bottom feedneck. Looks like you did take a pic of it after all lol.

[flyweightnate]

Try venturi bolts. Something like the Cyclone bolts, with a central stem to channel the air. That extra back pressure will help even out the velocity; put some o-rings on the stems so you can add some resistance by stacking rubber on the top bolt's stem.

... all while cackling like a madman.

[Headshotted]

Welp. I'll be taking my laptop to the bathroom.