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reliable feeding

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reliable feeding

Unread postAuthor: jackssmirkingrevenge » Sat Sep 19, 2009 2:48 pm

After a lot of development of full auto valves, I stumbled on the problem of a high capacity magazine. A gravity or spring fed magazine is limited in that more than 30 or so rounds aren't practical, the ideal would be to have a hopper but this will not feed well. The ammunition needs to be agitated in order not to jam at the breech, which is how most BBMGs work. The same setup is impractical for a pulsing valve however.

The concept here is that a spring loaded piston is included, knocked upwards by each blast of air. This serves to agitate the BBs while at the same time temporarily blocking off the hopper at the time of firing, allowing less pressure to be lost expanding into the hopper. Any thoughts on different configurations welcome :)
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Unread postAuthor: jor2daje » Sat Sep 19, 2009 3:05 pm

Looks like a pretty cool idea, I think it may be dificult trying to find the right balance between strength of the spring. If the spring is too strong you'll fire without reloading but if its too weak you wont be able to feed properly at high rpms.

Also I think you may need a small bleed valve on the chamber because your piston could act as a sort of check valve.
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 19, 2009 3:37 pm

The idea certainly needs refining, I have some other unlikely solutions, such as an air driven rotor...
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Unread postAuthor: noname » Sat Sep 19, 2009 3:38 pm

The main problem I can see is that without a guide rod, the piston would not reset properly. It also might catch a BB halfway into the breech, so that neither the piston nor the BB could fall into the breech.
I also plan on watching this topic closely and trying to give helpful criticism. Believe me, I want a working feed system too. :?
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 19, 2009 3:42 pm

noname wrote:The main problem I can see is that without a guide rod, the piston would not reset properly


Naturally, I took it for granted that there would be some sort of guide rod, this was just presenting the concept.
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Unread postAuthor: inonickname » Sat Sep 19, 2009 10:05 pm

Would probably work. (As noname said, you'll need a guide rod). You would need the piston to blast back far enough reliably otherwise there would be no feed at all.
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Unread postAuthor: noname » Sun Sep 20, 2009 12:23 am

I think it'll be hard to find a perfect balance in between no feeds and possible double feeds, along with the issue of jamming. I'd get too annoyed with the design personally. Finding a guide rod that wouldn't bend at longer lengths (bigger mags) would be too irritating for me. Good luck, I'm sure you can pull it off.
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Unread postAuthor: psycix » Sun Sep 20, 2009 6:18 am

What about this modification, to make them drop through the piston?
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Unread postAuthor: POLAND_SPUD » Sun Sep 20, 2009 6:35 am

studying how paintball hoppers work seem like a good idea click

on my semi auto I would have experienced a similar problem (fill a bottle with marbles you'll know what I mean) but it turned out it worked all right because the bolt has larger OD than the air cylinder rod + spring... so each time it is retracts to load new ammo one marble directly above it is lifted upward and as a result all marbles in the mag are lifted and 'agitated' in a way... somehow this proved sufficient....

I guess that air could be used to do the same job.... I mentioned it in hybrid bla bla bla BBMG thread...uhmm I think you know which one
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Unread postAuthor: psycix » Sun Sep 20, 2009 7:02 am

I believe the best hoppers have a rotor that forces down a ball each time it detects a shot.
You need some sort of moving part. There is no shape that allows random balls to drop into an hole without any possibility of jamming.
So either something to mix the balls randomly, shaking jams out of the way, or something that grabs balls and forces them down.

EDIT, seems like we cross-posted.
An air blast could indeed also unjam the balls.
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Last edited by psycix on Sun Sep 20, 2009 7:08 am, edited 2 times in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 20, 2009 7:03 am

Interesting point, maybe a well designed hopped doesn't need a piston or similar agent for agitation, just the air blast

Image

It's a complex shape to reproduce however.
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Unread postAuthor: POLAND_SPUD » Sun Sep 20, 2009 7:34 am

it worked well with a bottle as a hopper...
so my guess is that the complex shape might not be needed at all (besides... there is no such thing that can't be built with a bit of epoxy, right ?? :wink: )
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 20, 2009 9:05 am

I had used a foetal bottle as a hopper:

[youtube]http://youtube.com/watch?v=U_1cN7lhW5c[/youtube]

As you can see air along provides plenty of agitation, but the system was not very reliable, misfires and double feeds galore.

I think that plate that only allows one level of BBs above the feed hole is critical to reliably operation, hmmm...
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Unread postAuthor: POLAND_SPUD » Sun Sep 20, 2009 9:21 am

I doubt that double feeds have anything to do with the hopper... is there anything that stops bbs from entering the barrel??

I think that plate that only allows one level of BBs above the feed hole is critical to reliably operation, hmmm..
possibly... I rarely loaded more than 20 - 25 marbles...

I think I might find answer to that question using phun (don't laugh it's just computer assisted designing) :wink:
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Unread postAuthor: spudtyrrant » Sun Sep 20, 2009 9:36 am

Question, Why not just buy a paintball hopper and modify it for your needs?
You can get them fairly cheap.
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