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Old 07-12-2012, 08:22 PM   #11 (permalink)
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A lighter spring will not help. We tried both heavier and lighter. Lighter meant the assembly tried to destroy itself just that much quicker.

Ty
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Old 07-12-2012, 08:48 PM   #12 (permalink)
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Ball stack clipping is very unlikely unless the paint is super super tiny.

I just started tossing a few ideas around in CAD, this time looking at blowback potential more than the robustness as the dual springs seem to be at least in the right direction. I'll shoot you a message with a few ideas once I've had a little more time to ponder them.
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Old 07-12-2012, 09:14 PM   #13 (permalink)
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A lighter spring will not help. We tried both heavier and lighter. Lighter meant the assembly tried to destroy itself just that much quicker.

Ty
Then would a longer throw help? so the bolt went further into the breech making more of a seal

It works in my head lol
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Old 07-12-2012, 09:41 PM   #14 (permalink)
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Longer throw isn't a good thing because you end up with over-travel. The back end of the bolt actually passes into the breech. Then you get massive blowback. The dual springing helped out a lot. I'm still tweaking the timing. I'm actually going to be swapping out to a nice raw, partially milled macdev frame/oled board that should allow me to time the valve more specifically. I believe the blowback is mainly coming from very, very small amounts of air between the body and bolt (minimal) combined with the air pushing the bolt getting released prior to the main thrust. The bolt at this point at least seems like it'll be tough enough to survive the pounding it takes.

Lighter springs aren't really do-able because of the speed of the bolt going forward, stopping, and resetting. It'll destroy the spring in literally a couple cycles. It also really kind of kills the ability to reset the bolt consistently. Ball clipping is doubtful but I can't completely rule it out, so I will check again. All it takes to notice the blowback is putting your hand above the feedneck. The tougher bumper-spring seems to have help a decent amount. I may also try to drop an o-ring in the feedneck, and see if that locks paint in a little better. Yoda, let me know what you're thoughts are. Alpha, if you're out there and have any ideas, I'd love to hear them.
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Old 07-13-2012, 10:50 AM   #15 (permalink)
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I'd look to make a longer, heavier bolt with a longer throw. That will, at very least, calm things down.

After that, I'd try to redesign the bolt to have a significantly smaller pressure-bearing surface. You have what looks like an extremely tight venturi, which means the majority of the profile is acting as a piston to shove that bolt forward once air gets around the first barrier. If you're at 250psi, you want less than .05 in^2 piston face, or you need a 10lb spring to balance it. Shrink that piston surface as small as it will go.

Supposing you cloned the Aedes animation perfectly, and your bolt OD is .750", an ID of .650" still gives you around 13lbf at 250psi. That's a hefty spring. You want the balance to be as close to zero as possible, and you need to tighten everything up (inside and outside of the bolt) to prevent air from passing the bolt and heading up your feedstack. Tolerances have to be pretty tight, so you might need to look into brown delrin instead of white, or some more advanced polymers.

Edit: to specify, the different polymer choice would be because white acetal can be very dimensionally unstable depending on temperature and lubricant choices. If it changes at all, that could be where your air starts circumventing the tail of the bolt and heading up your feed stack. I don't remember if it was Apoc or Alpha who specialized in polymer manufacture, or someone else... Also, if the tolerances on the back of the bolt are tight enough, the venturi shape is only relevant to the bolt destroying itself from all the pressure, not as much to the ball clipping issue.
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Old 07-13-2012, 04:49 PM   #16 (permalink)
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Yeah, Longer bolt with a longer throw,left that part out,

If the front of the bolt was similar to the cure bolts would that help the clipping? I know that would mean you would have to put an oring but I believe it would help
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Old 07-13-2012, 06:38 PM   #17 (permalink)
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I've thought about taking that from the eclipse bolts too. Say whatever you want about the eclipse guys, but some of their engineering just makes a lot of sense. That may be a mod worth doing.

Lengthening the bolt would require the entire body to be re-worked. You'd have to change the feedneck/air vent ports/location of the MQ2. We're hoping to avoid that.
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Old 07-13-2012, 10:31 PM   #18 (permalink)
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Can't cut a ramp onto a bolt that can't be indexed

The bolt is only .668" on it, ball clipping is very unlikely to be an issue unless you are somehow getting double feeds - also unlikely with that small a bore, but possible with how small paint is in some areas. The bore in an Ego is significantly larger than in most guns, that is part of why ball clipping was an issue in them, the top of the bolt was higher than the top of the paint once it was settled into place in some cases.

A heavier bolt is going to do more harm than good I think, damping the thing is difficult enough as is without increasing the cyclic mass.

Longer throw is the main thing I was looking at, but we can only get it a little longer due to where the transfer port in the body is located. I'll figure out exactly how much longer it can get though. I can give Ty the dimensions to cut the powertube part to, and I can make you a longer bolt to try out.

There just isn't enough room with the brass body to put any o-rings in to take up the slack and eliminate blowback, and the step that is in the bore makes taking up that slack with a tighter clearanced bolt problematic because it will just shave it away. The other problem is that you can't have everything sealed, or the bolt will not retract because it will have to fight against an air spring with the air trapped between seals. If it could have been better sealed without causing problems, I would have.

The issue with the forces generated on the bolt are also determined by needing a decent flow path for the air. Make that area too small, and the system is too restrictive. The venturi is actually not too bad a restriction, it has a total cross sectional area equal to a .303" hole. Granted, there is more drag from the edges compared to a single hole, but it isn't too bad, and is only exposed to the air for the last 3/16" of throw or so.

Actually, if Ty can pop off that rear part of the top bore (it looked like it is a separate piece, but I couldn't tell for certain), then doing so and smoothing out that edge of the bore would let a bolt with tighter clearances be made. Replacing that with a piece that has no step would actually be even better, or a step that didn't start until right in front of the air port. Definitely not the preferred method due to the work involved, and probably best saved for a last resort,
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Old 08-05-2012, 09:37 PM   #19 (permalink)
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IT FINALLY FRICKIN' WORKS!!!!

So I went out and played with Ty and a bunch of his guys today. Beyond having a great time playing with them, I also brought along the Aedes with it's new frame and a board. Last night, my new Frenzy frame with an OLED Ego board came in. It allowed for much more precise bolt control. I also was able to tune the bolt springs down, setting the bumper spring (cut down sheridan main spring) to the correct length, and get the mainspring tuned in.

We were able to put about a hopper and 4 pods through it. Only a few breaks, mainly when the air was dying down. It does need a little tuning, but we're talking tweaking it versus holy-crap-it-exploded-again. The respringing and timing from the board seem to have killed the problems that it was having. Big, big step forward. I'm a very happy human today. Here it is as it sits. It'll have a black durocoat over it soon.




Thanks again to Ty and Jonathan for the work that they've put in over the past year and a half.
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Old 08-05-2012, 10:34 PM   #20 (permalink)
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The end of an era... One more prototype out the door... Jonathan, I could *NOT* have done this without all of your help and expertise! Thanks for all the hard work.

Ty
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