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hybrid cartridge protoype without burst disk

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: POLAND_SPUD » Tue Sep 13, 2011 1:48 pm

as hotwired said... with standarised parts you should be able to simplify the design

Have you considered getting rid of that copper part from the back of the cartridge ?? Not sure if there exist screw with such a large head but there must be something that can replace it

that's one less part for machining
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 13, 2011 6:34 pm

POLAND_SPUD wrote:that's one less part for machining


When (not if) you get your lathe you will realise this is no trouble at all. I could happily churn out 25 of these cartridges in a single evening.

This was my first though for simplifying it, making the rear plug fixed and using the projectile as a valve:
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 16, 2011 12:33 am

Another variation, this time with a fixed rear plug and single o-ring sealing both forward plug and projectile. I reckon I could make this 7mm ID/9mm OD and 45-50mm long for a 0.177" projectile, giving a "realistic" cartridge size and reasonable power at high mixes.
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 17, 2011 5:50 am

Work in progress according to the above design, rear end plug is now epoxied in and curing, just need to drill holes for the pins.
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Unread postAuthor: wyz2285 » Sat Sep 17, 2011 3:46 pm

Sorry I only post now, actually a little after jack posted "mini hybrid win" I got the I idea of combine valve less with it. Got a try, accident happened(epoxy of ne end exploded, almost killed me) so I stoped. But after make a better plan I decided to give another go. So my only concern is will the 1mm wall brass tube hold a 30x mix?
diagram, I´m also worried about the ignition, I will use a tazer, but will the spark pass a 30x mix?
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Moonbogg » Sat Sep 17, 2011 11:10 pm

Its lookin pretty good. Keep at it!
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 18, 2011 12:17 am

Moonbogg wrote:Its lookin pretty good. Keep at it!


Hmmm...

[youtube]http://www.youtube.com/watch?v=glH0nTLitP4[/youtube]

It holds pressure well enough but couldn't get it to ignite at 10x. Eventually got it to ignite at 20x but as you can see, I missed one of the pins falling out.

Needs some work.

So my only concern is will the 1mm wall brass tube hold a 30x mix?


If the epoxy is good enough it should hold, though it might develop a leak used repeatedly at such high pressure.

I´m also worried about the ignition, I will use a tazer, but will the spark pass a 30x mix?


Make sure the spark gap is below 1mm and you should be fine.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 18, 2011 7:00 am

Some further testing, took it right up to 28x and no joy. Video at 210 frames per second, if you look at the rear part of the cartridge it glows indicating combustion half way through the clip:

[youtube]http://www.youtube.com/watch?v=c-mMnQ51A6c[/youtube]

The detent however is simply too good :roll: it doesn't help that the o-ring is compressed further by the hot gasses, increasing its grip on the BB.

According to HGDT, internal pressure exceeds 3000 psi.

The Delrin seems to be holding up well to the high temperatures.
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Unread postAuthor: jhalek90 » Sun Sep 18, 2011 7:05 am

i tried, what looks to be a similar sized oring, with a .177 BB in a penu, I was unable to get it to pop at 1000 psi... and stopped there.

I am very surprised that it did not pop at 3000 psi though!
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POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: POLAND_SPUD » Sun Sep 18, 2011 9:12 am

I loled @ devilish glow :)

Theoretically speaking you could go past 28X and see what happens :-D
Though I guess it would be easier and safer to use a different o-ring
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Unread postAuthor: wyz2285 » Sun Sep 18, 2011 9:14 am

ya I was also amazed about the detent power of a o-ring, even it looks and feels so easy for a bb to pass, it still needed more than 300 psi to work in my case, so now I make my detentes out of a rubber cube :P and worked great
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 18, 2011 11:02 am

jhalek90 wrote:I am very surprised that it did not pop at 3000 psi though!


Internal diameter is 3mm - 1/8", I tried using a 3mm bearing with the cartridge but it's too loose.

Theoretically speaking you could go past 28X and see what happens


I'm sticking to atmospheric pressure fuel metering for now, besides the design compresses the o-ring the higher the pressure so I don't think upping the mix is a solution.

Though I guess it would be easier and safer to use a different o-ring


The next o-ring size is 4mm ID/8mm OD so it could be done.
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Unread postAuthor: POLAND_SPUD » Sun Sep 18, 2011 11:12 am

so if it works... how much do you charge for one cartridge ? :)

.117 is wimpy but a 6mm or 9mm lead BB cartridge could be pretty impressive... esspecially considering the miniscule chamber volume... I sense a possible suppresed hybrid

Damn I wish I had a lathe (envy)
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 18, 2011 11:35 am

POLAND_SPUD wrote:so if it works... how much do you charge for one cartridge ? :)


If I perfect it I suppose I could offer a limited run of say fill rig and 5 carts for under 50 euros...

.117 is wimpy but a 6mm or 9mm lead BB cartridge could be pretty impressive... esspecially considering the miniscule chamber volume... I sense a possible suppresed hybrid


That's the long term goal, really I want it to use 0.22" pellets but wanted to try something smaller because a hybrid "pocket pistol" is also on my list :)

Damn I wish I had a lathe (envy)


Surely you can get a good second hand deal?
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Unread postAuthor: POLAND_SPUD » Sun Sep 18, 2011 11:42 am

Surely you can get a good second hand deal?
well yeah but that would consume my monthly income :(

for under 50 euros...
seems like a reasonable price

I want it to use 0.22" pellets but wanted to try something smaller because a hybrid "pocket pistol" is also on my list
who said you can't build a pistol in 0.22" calibre ? [/img]
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