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20mm autoloader

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20mm autoloader

Unread postAuthor: Tostitos » Mon Jul 24, 2006 6:21 pm

I drew out plans for an air and electrically powered minigun that would shoot foam bullets when I was eleven. Just sayin'. They wouldn't have worked, but they were the start of something workable.

Now, forget all that. I don't think anyone without the help of a few graduate level engineering students and a fully equipped machine shop can make a minigun that shoots bbs, airsoft, darts, nerf, golf balls, or whatever. I do have a few ideas that would fix a lot of timing issues if the barrel cluster rotated independant of the load and fire mechs- but it's pretty much pointless aside from "cool" factor. I want something that operates without having to sink years of my life and my entire savings into it.

I'm thinking about making a 20mm tri-barreled cannon. I've worked out how it would feed (partially) load and fire. I'll build a model first in PVC, and then later on, a finished production in steel.

These are my design challenges:

Maintaining a sufficient supply of compressed gas for rapid (600+rpm) fire. Dry nitrogen?

A suitable magazine system that would smoothly feed in the ABS / organic matter slugs into the feed mechanism. I think a large drum would work with my concept for a springloaded multitrack follower.

Having the magazine feed system go directly to the breech could result a slug being pushed into the moving face and being shorn / mutilated, so the magazine would end at a feeder claw that would move in sync with the receiver unit to load in a round at a time at the needed speed.

Once the round is inside the breech, the unit will make either 1/3 or 2/3 rotation, then fire. ( http://www.pureluckdesign.com/videos/Gau17animation.wmv )The breech will need to seal somehow when firing, so possibly it can rotate past a seal, or have a block clamp down as part of the firing operation to provide a breech seal.

Hey, at the least, I'll wind up with a semi auto pneumatic (propane might work better because there's no problem with maintaining a high pressure supply- but I get a bit nervous about the idea of a fast firing gun using that if there were a few cycles that failed to detonate followed by one that did...) that shoots at least one slug per second with a crappyass feed system and lag for repressurization.

I can't find any google info on Index Valves but from what I read about them in the one post on here that has a guy being eulogized (rest in peace, cool guy) it seems like I could use it to automatically handle six or more compressed air sources to go to one tube, sort of backwards from the idea of how it should be though.

http://www.midwayusa.com/eproductpage.e ... mid=554245 might end up being a crucial part of my feed system ;)
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Unread postAuthor: Tostitos » Mon Jul 24, 2006 9:02 pm

Here's my initial crude sketch:
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Unread postAuthor: M3NT4L » Mon Jul 24, 2006 10:31 pm

:) Thats a pretty sick idea but it will cost you alot of $. When you are finished with it post some vids.
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Unread postAuthor: Tostitos » Mon Jul 24, 2006 11:07 pm

I see accessories like butterfly trigger spade grips being most of the cost...
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Unread postAuthor: Tostitos » Tue Jul 25, 2006 10:30 am

Here's my first obstacle: maintaining a metric fuck-ton of air into a rotating cylinder. If the barrels were spinning but the rest stood still, it wouldn't be hard (then the feed system would be hard instead, trying to throw something into a spinning hole every few milliseconds) but that's not how I'm doing it.

The image demonstrates my first idea: valves on each chamber with a unified air supply behind the breech. The cylinder would rotate, the air supply would not, and it would have a connection at the rear for c02 or a compressor. The seals would maintain air pressure even with the moving parts- at least that's how it would have to work. I'm not sure if seals even exist for that sort of application.

Also, the air supply would be shaped like a donut to allow for a shaft from the center of the rotating cluster, for stability. (The motor and clutch will be to one side of the cluster, not behind the air system)

As for the left hand image, that's a diagram of how the housing and ejection ramp will be placed. In case of a misfire, I want to remove the projectile so there will be an ejection ramp at four o'clock.
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