SpudFiles

edit: the concept has been revisited with much more success here.

This was a prototype i made to test a concept of pneumatic cartridge feeding and ejection i had come up with back in glory days of spudtech

I know it looks extremely ghetto but the intention wasn't for it to be pretty, it just had to work. Here's a few videos, scroll down to the diagrams and photos attached for details:

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single catridge ejecting viewed from the side


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single cartridge ejecting viewed from the top


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yes, it actually fires a projectile, excuse the poor accuracy but it's hard to fire the thing and hold a camera at the same time


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due to some reliability issues with feeding when I added a magazine for consecutive shots, I eventuallu added a bolt-stop that had to be manually activated in order to feed a new cartridge. As you can see above this worked successfully, even in a prototype that was literally held together with tape, but I stopped work on the project after realising that while it looked pretty cool, power wasn't going to be all that great.

For more detailed information on using epoxy, check out the how-tos here and here.

i think u are my new hero
that is awsome i woudl love to see a pistol desgined around that

HOLY HELL!!!! that is freaking nice, man how long have you worked on that thing??

got any stats. eg fps, running pressure?

conclusion: very very kool, cant wait for it to be used in a designed stock/gun

peace
chaos

I made it over the space of a week, what takes the longest is waiting the 24 hours the epoxy needs to cure.

I was using 110 psi from my compressor (you can see the schrader filling attachment in the last video), never measured the muzzle velocity (I was using 0.22 airgun pellets flared out to fit a 6mm barrel) but it was very weak. If you look at the smiley target, you'll note that there's a dent where the projectile struck below the face but it didn't actually penetrate the cardboard backing the target.

I remember that well. It actually aided and abetted some of my cartridge loading ideas (You may well remember some of what I said in your thread).

My brother has now "borrowed" those ideas, and with any luck, he'll soon start the building process on the cannon that will use them.

i seriously think you are jesus....

ive thought about something like this, but i always had the air coming in from the back. altho it looks very ghetto, that doesnt matter cause it works, and its good.

i seriously think you are jesus....

Yes, my son, appropriate avatar don't you think

I remember that well. It actually aided and abetted some of my cartridge loading ideas (You may well remember some of what I said in your thread).

Yeah, had some time to spare so thought I'd repost some of the old spudtech stuff that might be of interest to those on the forum who haven't seen it yet, it's nice to see people build on your ideas and experience.

You do know the competition is coming up? I would love to see that design you never built in it

*whistle*

dude... that is absolutely awesome. please dont stop ur work, im sure u will eventually get some serious power out of it somehow. the ingenious design is reason enough to complete the project!

Slick. I remember this from spudtech. You should try for something like a revolver.

how well did that piston-based design work? I've been thinking of making a precharged using a fire extinguisher for the reservoir and something like that piston set up for actual firing.

Some more thoughts on this concept... Perhaps the bolt should be housed in a cylinder that allows it to be airtight or reasonably so as it blows back for a further distance. It looks like the air shoots the projectile and the casing back but then right away there is an open vent at the magazine slot for air to exit and bleed off power.

If the bolt was designed more like a low friction piston and traveled back a couple of inches before there was any loss of air as it passes the magazine or ejection port it would have a bit more power.

I'm working on that concept now. The gravity feed magazine will be several inches back and the ejection slot even further back towards the limit of the bolts rearward travel.

Hopefully it will have the capacity to sustain a range of shots from 300 psi on down to whatever the lowest operating power is.
Definitely it will have a long spring cushioning the bolt travel for those first few shots.
It will also be scaled up and shoot cartridges holding marbles. This will require a mix of copper and pvc, but using those two materials allows a perfect blend of materials that already fit in every way without requiring any machining etc.

what kind of piston is that?

You the jesus of spuds, you have toiled in the depths of hard working hell to get this to work, and you shall be reborn! anyway, great job, i would love to see what u do next (bouncing up and down a squirrel on ridilin) seriously dude can you give us a hint about ur next design or do they just come to you in waves of BRILLIANT ideas?

What i'd really love to see is a more in depth description of how to build one of these things with a list of materials etc. if you do that you'd be my hero for life