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Pre-charged cartridge suggestions?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Pre-charged cartridge suggestions?

Unread postAuthor: inonickname » Thu Jan 21, 2010 2:07 am

I've been building some pre charged pneumatic cartridges recently which use an unbalanced spool valve similar to the brocock air cartridge. I've had no problems making the cartridges (and the spool valves) as I have a lathe to play with. However, I'm running into some problems with filling them. I want to make a filling dock to charge one cartridge at a time though I'm unsure of how to secure them to the dock.

The spool valve also needs to be held open (otherwise the cartridge will not fill). I was thinking of threading the cartridge, but that runs into several issues.. or perhaps a dock which the cartridge is placed in (sealed by an o-ring at the top) then a screw closes the breech underneath the round and opens the valve to be filled.

Any ideas?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 21, 2010 2:35 am

Nice, can we see them?

If I recall correctly Brococks where filled by screwing them into an adapter. You could also have something which clips on to a rim, I've seen something of the sort recently :roll:
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Unread postAuthor: USGF » Thu Jan 21, 2010 4:35 am

jackssmirkingrevenge wrote:Nice, can we see them?

If I recall correctly Brococks where filled by screwing them into an adapter. You could also have something which clips on to a rim, I've seen something of the sort recently :roll:


Really?

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Unread postAuthor: jackssmirkingrevenge » Thu Jan 21, 2010 4:48 am

The first rule of cartridge club is you do not talk about cartridge club :D
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Unread postAuthor: inonickname » Thu Jan 21, 2010 11:35 pm

Image
It still needs substantial improvements. It needs a charger, a longer firing pin (this one doesn't reach to the end of the cartridge), a way to house the ammunition and a way to stop it mauling the orings, but it's a start.

The idea is that the hammer opens the unbalanced spool valve by forcing it forwards. I don't know how, but on brocock cartridges the valve seems to retract backwards. Anyone know the exact workings of these?
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 22, 2010 12:04 am

Looking good.

Filling procedure illustrated here.

Image

Unscrew cartridge pellet cap

Image

Push spool into cartridge body

Image

Insert cartridge body into charger and fill with compressed air

Image

Drop pellet into pellet cap and screw onto cartridge body

Not quite the design I'd want to replicate but they're interesting little things.

Image

On an almost related note, turns out Brocock air cartridges are available quite cheaply! :shock:
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Unread postAuthor: inonickname » Fri Jan 22, 2010 12:12 am

Ahh I figured out how they work (as in-open backwards). It's quite complex to do on this scale (extremely).

http://www.google.com/patents?id=BBorAA ... q=&f=false

It hit me on page 8. The gas is trying to force the larger side back, but it is retained by a makeshift sear (such as bearings) though when the sear (firing pin) is forced forwards the sear can open (bearings move inwards), allowing the piston to actuate.

The only upsides that come from this are slightly more flow (but you wouldn't make something like this for power), perhaps better filling and lower actuation energy, but that amount to work for a single cartridge is unthinkable.

P.S. probably going in a low energy target or cane gun.

By the way Jack;
Image
How are they filled without leakage around the firing pin?
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 22, 2010 12:17 am

inonickname wrote:How are they filled without leakage around the firing pin?


It's clearer here, the charger is enclosed:

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Unread postAuthor: inonickname » Fri Jan 22, 2010 12:20 am

Oh, nice. So the spring and the firing pin are used as a check valve I see? Very ingenious.
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