Rotabolt gun. Theory, Diagram, Ramblings Inside.

[Lurker27]

Cross Post form tinkerers guild.

I was thinking of another project to do, when an idea popped into my head. For prototyping, it can be based on a spyder.

The idea is to chop off the front of a spyder bolt (delrin would be best, since it needs to slide nicely) and make a small (delrin) plate to seal the breech from the feedtube (trap door design, pretty standard). Air is constantly fed through the body hole of the spyder via a plugged blowback port in the valve and lack of a valve pin/cupseal assembly.

The cycle is run through the ACE. When a ball is detected, the breech is sealed by the plate, which, since it doesn't require much force, could be run directly by a low-power solenoid (solenoid could be held closed via spring and energized to open to save batteries).

The firing cycle itself would use a vertically oriented ram to rotate the bolt assembly , briefly lining up the inlet of the valve with the body hole and allowing a burst of air through. I'm thinking enlarged body ports are in order, and the the body hole would be lined with 'liquid gasket' to provide a good seal. Because only one ram is needed to trigger the firing cycle, any old board would do.

You might be thinking that the problem you'd run into is efficiency, but, if one were to have a bolt with 2 ports and a ram stroke such that the rotational action was ratcheting and turned the bolt 180*, you'd have a dwell that was transitive, rather than reciprocating. This would lead to shorter dwell times, but at full flow. Creative structuring of the port could help to even out the graph of flow over time during a syzygy of the 2 holes. (Naturally, it is a bell curve with the most flow in the middle)

I think that this could help to solve the efficiency problem, by packing a very short dwell in. in most other markers, short dwells decrease valve dwell, but also can decrease flow by not opening the poppet as far. In theory, LP air could be dumped quickly and allowed to expand adiabatically behind the ball, while the bolt continues rotating to seal off the barrel making for an extremely efficient marker. Hopefully you could get the air dumped and the valve closed again before the ball leaves the barrel.

Also, because there is no obstruction in the breech, in lieu of detents one could create a C-shaped UHMW barrel insert (running the entire length of the barrel) that clamps when the ACE sees a ball (again, the default position could be closed, set with a spring and relaxed via a solenoid when a ball is not detected). The clamping UHMW insert would provide for a perfect paint to barrel match with each shot, improving consistency, accuracy and efficiency. UHMW is a flexible but reasonably strong, slick and hard material (harder than a paintball) that would be good for this application. since you know the relationship of the bore in relationship to the paintball with every shot, you can do interesting things like applying internal rifling and be sure the ball is taking the spin, or purazor blades set ever so slightly out of thwe UHMW sleeve to slit paintballs ever so slightly, increasing their chance of breakage on target.

The characteristics I can see provided by this design:

Speed. No reciprocating mass in the pneumatic cycle, so CPS is limited only by the ram.

Kick. Should be nonexistant, as the only reciprocating part is the breech sealing plate, which should weigh no more than a paintball.

Efficiency. If leaks can be avoided, you can the potential for a very short dwell at high flow rates. That spells efficiency, to me.

Accuracy. This has more to do with the barrel concept, but if rifling could be successfully applied, (and there's no reason it can't, in theory) you'd have a deadly accurate marker, since every paintball had the barrel clamp specifically to it.

Size. The bottom tube is not required. If the ram was located in the frame (not unrealistic since it sits veritcally) and no LPR wa used (ala SP) you could have a complete valving system aobut the size of a mag valve.

Complexity. A definate disadvantage, here. The face seal that the rotating valve necessitates is hard to accomplish. The ACE would control so much, you'd have to have them super reliable and be able to see through paint. WAS eyes do half of that. the ratcheting system would have to be very reliable and consistent, as well. Teh trap door must be carefuly placed as to not become a ball guillotine.


Battery Life. Using solenoids to open the breech and relax the barrel/detent system will suck up juice, but probably no worse than an E-spyder since neither enterpise takes much work (Force x distance) I don't imagine electrical shootdown would be a big problem.

Choppage. Since nohing solid contacts the ball, there shouldn't be any. Since the barrel will size even to the odd balls in the batch you shouldn't get too many breaks. The ACE should help too.

I'd love to hear what you guys think of this pipe dream.

[coolcatpete]

sounds goo, but it may be hard ti do it sounds like.
Pete

[Mango]

lets think...you want to shoot paintballs, out of a barrel, that has "razorblades" in it? You MIGHT want to hit the think tank one more time.

[Lurker27]

I was simply using a generic term. The idea is that, because you are controlling the position of the paintball relative to the wall, you can make however deep a cut you want in the shell you want. even a large scratch on the shell is enough to create a stress riser, which acts like the seam, concentrating force on a part of the shell to break it.
Consider the following: A paintball hitting on its seam is 5 times more liekly to break than a paintball hitting on the "pole". If you can artificially increase the number of seams (read: stres risers) on the shell of a ball, you're increasing the chance of hitting one, and therefore increasing the chance of breaks on target. If you can't fine tune it well enough, simply take the "blades" out and use as a standard barrel kit.

[1stdeadeye]

How are you going to line the seems up?

It seems like you would have lots of barrell breaks with that system.

Good thinking though!

[Lurker27]

Which seams? The paintball seams? Those would have a random orientation. Any sort of sharp guides, blades, whatever would be simply evenly spaced around the interior of the UHMW insert.

[FutureMagOwner]

well i think besides the razor blade idea it sounds good but i dont think your going to get the paintballs to not hit on the seams, because of the inconsistant bore sizes in paintballs themselves amongst other things. and to quote brain fellow "Thats crazy!!"

[Lurker27]

I think that my post is putting misconcpetions out there...The position of the seam only affects breakage ON TARGET...this gun design wouldn't particularly care about them, even with the questionable blades idea.

The inconsistency between patinballs, even in the same batch is the reason for the clamping barrel system. as far as the relationship of the surface of the barrel and the paintball is concerned, its constant, because the ACE sizes each shot independent of the others.

[paintballrulzs]

What would you do if a paintball were to break. You can't exactly squegee it

[Destructo6]

lets think...you want to shoot paintballs, out of a barrel, that has "razorblades" in it? You MIGHT want to hit the think tank one more time.
I believe this was done and marketed quite some time ago, say 1993 or so. It was intended to score each ball as it exited the barrel to ensure reliable breaks. This is a time when paintball shells were pretty rubbery.

[personman]

Interesting.

You're crazy. :tard:

[firebanex]

sound like a good idea. good luck with it.

[Lurker27]

This is a little disorienting...I was kinda expecting a fatal flaw in the design to be pointed out to me within a few hours of posting...so far so good, myabe it'll get out of vapourware.

[Destructo6]

If you want fatal flaws, I believe the rotating bolt/valve is it. It would seem that in order for the seals to be effective, they'll have to be so tight that the bolt would only rotate with great effort.

The barrel is overly complicated. It would be a neat project, which if that's all this is, I'd like to see the results, but it's hard to see how it would be significantly better than a good conventional barrel.

That's my 2 cents, feel free to ask for change.

[Lurker27]

That's definately where I was thinking the problem lies....mkaing an effective face seal and not chopping it up via the action of the bolt. It needs a compressable material, there's not much doubt about that Perhaps a delrin sleeve, or at very least polished aluminum would be necessary for that portion of the body. in addition, I think stiction induced FSDO could pose a problem. Instead of the 2bolt orings, using airtight rotating fittings would reduce the friction significantly...Something in slightly larger quick disconnect fittings, bored out for higher flow, of course. I'm sure McMaster has somehing like what I'd want. There's still the issue of the face seal surviving, but I think a delrin bolt with a stationary gasket on the body would produce the best combination of coefficient fo friction, gasket surviveability, and effective sealing.

I remember particularly well a post that had Tom griping about o-rings...to be effective they have to be slightly undersized and stretched to fit. I was thinking that the easiest way to do this particular one is via a product known as liquid gasket...basically a rubber with plasticizers that evaporate to leave a gasket where you want it...Angel users have been using it to create a face seal in the rotabreech, with pretty good results.

As for the barrel, it's complicated, but its also the equivalent to a kit with a basically infinite number of inserts, with the inserts adjusting individually to each paintball. It would become REALLY effective if one could include some sort of rifling scheme, in my opinion. Theoretically, rifling would improve the performance of an imperfect sphere as a projectile, but its always been a problem with implementation. I don't see how a barrel with a stationary set of grooves can impart spin on everything from Hellfire to Big Ball. seems like it at least some, if not most shots, you're shooting a lumpy smoothbore, and such inconsistency can only hurt accuracy.

You've relly helped revise the design...I think that with a stationary gasket, delrin bolt, and rotating couplings rather than additional rotating orings, its far more viable.

[Destructo6]

Theoretically, rifling would improve the performance of an imperfect sphere as a projectile
AGD did some spin testing a while back and concluded that, because paintballs are not solid and are relatively light, spinning produced very little to no improvement in accuracy.

http://www.automags.org/resource/tech/tomstech/03_spinning.shtml

[Lurker27]

Not to derail my own thread, but I've seen that link and disregarded it. That test was done YEARS ago.

Glass of ice water? the fill doesn't spin? the spin won't take. /me points to the flatline barrel. Ok, you can spin paintballs, that's been done. Already part of that "tech tip" is utterly incorrect.

No improvement in accuracy? Well, of course not if he's using perfectly round paintballs! The paintball inaccuracy that Tom is talking about is knuckleball effect, caused by the random orientation of the seams of the paintball when it drops. Even if you impart NO spin at all, the ball will begin spinning due to vortices being created behind the seams. As the position of the seams was random to begin with, this induced spin, and the forces it create that cause deviation from an ideal flight path, is also random, thus creating a spread. This is the last factor that we can control in paintball flight.... we control velocity, we control spin, we control angle. EVERYTHING ELSE is environmental. At the very least, spinngin a paintball breaks even. In theory, its more accurate...maybe we should stop denouncing rifling as a whole as hype and look into it as a viable technology.

As for the design, I did some thinking on it. and decided that QD type fittings are unecessary, but rather, simple bearings would be a better choice there.....no modding required, just machine the delrin bolt/valve assembly to fit.

[i bunkered u]

wo. most of this is mumbo jumbo to me but let me know when its all done and this thing rips! lol!

[evan123]

Yet another thing of lurkers flies over my head.