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Community Project #1 - Handheld, High Mix, Hybrid

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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Community Project #1 - Handheld, High Mix, Hybrid

Unread postAuthor: Hubb » Tue Sep 22, 2009 5:19 pm

The objective for Community Project #1 is to construct a hybrid launcher that is regularly fired at 10x mix, is comfortable enough to be held before, during, and after being fired, and has a rate of fire of one round at least every 20 seconds.
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Unread postAuthor: Pookydarts » Tue Sep 22, 2009 5:42 pm

I know next to nothing about hybrids, and I've seen it suggested at least two or three times by JSR and others

But here goes:

A 'shell' precharged with mix, with a screw cap securing a coke can base burst disk up against an 'o' ring for sealing.

The screw cap is turned on a lathe with a reduction in diameter from say 1.5" to .5" and also contains a .5" lead or otherwise hollow base slug.

This is dropped into a giant bolt action and the front end is aligned with the barrel by something like a morse taper with a few 'o' rings in it.

The 'shell' IS THE COMBUSTION CHAMBER and is ejected with it's heat and post-burn gasses.

Shells would be very heavy, expensive, and time-consuming to build and 'reload' but rate of fire should be well over 6/minute and more like ten.

Did I mention my Dad's just bought a metal lathe!?! :D

All I'd need would be the electronics guys to get the electrickery into the shell to spark the whole thing off... :roll:

Just an idea, let the evolution begin!
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Last edited by Pookydarts on Tue Sep 22, 2009 7:06 pm, edited 1 time in total.
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Unread postAuthor: Moonbogg » Tue Sep 22, 2009 5:51 pm

A cartridge system is interesting. An alternative could be to use a multi chamber method where the chambers rotate. This would allow rapid loading and firing and would allow the chambers to cool off a bit between shots while still keeping the size of the chambers large enough to actually send something down the barrel.
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Unread postAuthor: jeepkahn » Tue Sep 22, 2009 5:58 pm

oooh, pick me pick me...

Seriously, this sounds like a design I've been playing with for a hybrid...

coax piston valved hybrid with on board 10x compression...

Keep the combustion chamber relatively small, the pistons pilot volume would be calculated so that the piston will be 100% seal both directions and the pilot volume would be "captive" making it air sprung with enough captive pressure to hold the 10x mix but with enough volume to allow full flow under combustion pressures... Now, you have a compression chamber(stirrup pump style) that is 10x the size of the combustion chamber, connected to the combustion chamber via checkvalve, and a fuel air supply feeding the compression chamber the proper mix...

You extend the pump, drawing in the mixture, you compress the mixture into the combustion chamber, you pull the trigger, BANG...repeat as neccasary.... there will be more calculations, but I hope you get the jist of my idea...
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Unread postAuthor: Moonbogg » Tue Sep 22, 2009 6:39 pm

A napkin sketch would be helpful
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Unread postAuthor: Pookydarts » Tue Sep 22, 2009 7:40 pm

Hate to say it, but isn't that similar in function to a honda lawnmower engine with a 10:1 compression ratio and a barrel instead of an exhaust header?
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Unread postAuthor: ramses » Tue Sep 22, 2009 8:43 pm

jeepkahn wrote: Now, you have a compression chamber(stirrup pump style) that is 10x the size of the combustion chamber, connected to the combustion chamber via checkvalve, and a fuel air supply feeding the compression chamber the proper mix...

You extend the pump, drawing in the mixture, you compress the mixture into the combustion chamber, you pull the trigger, BANG...repeat as neccasary.... there will be more calculations, but I hope you get the jist of my idea...


The only problem would be the insane force required to compress said mix. For a reasonable size chamber (several cubic inches), you would have to put the gun on the ground and jump on the pump to achieve the needed compression. Then you deal with shock heating and maybe a diesel.

It would be more reasonable to use something like 2x/pump or something.

and as to the piston valve with the "captive" air, that was pretty much my contest entry, and it does work. Even though I lost :(
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Unread postAuthor: maverik94 » Tue Sep 22, 2009 8:55 pm

Never done I hybrid, but I like the Idea of a cartrige, how bout a a bolt action clip-fed hybrid?
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Unread postAuthor: Ragnarok » Tue Sep 22, 2009 9:05 pm

maverik94 wrote:How about a a bolt action clip-fed hybrid?

Sounds like it would be more trouble than a magazine fed one.
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Unread postAuthor: jonnyboy » Tue Sep 22, 2009 9:27 pm

ramses wrote:
jeepkahn wrote: Now, you have a compression chamber(stirrup pump style) that is 10x the size of the combustion chamber, connected to the combustion chamber via checkvalve, and a fuel air supply feeding the compression chamber the proper mix...

You extend the pump, drawing in the mixture, you compress the mixture into the combustion chamber, you pull the trigger, BANG...repeat as neccasary.... there will be more calculations, but I hope you get the jist of my idea...


The only problem would be the insane force required to compress said mix. For a reasonable size chamber (several cubic inches), you would have to put the gun on the ground and jump on the pump to achieve the needed compression. Then you deal with shock heating and maybe a diesel.

It would be more reasonable to use something like 2x/pump or something.

and as to the piston valve with the "captive" air, that was pretty much my contest entry, and it does work. Even though I lost :(


There's no rule about the minimum chamber volume volume, I say we
go small first then if the idea works well work our way up to a larger size.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 22, 2009 9:56 pm

I'm on board with the cartridge idea :D

I think my straight blowbackcombustion concepts would be slightly relevant, why make it bolt action when you can have semi-auto? Flying brass, plus it offers an interesting possibility to help with recoil mitigation:differential recoil

Basically, the spring loaded bolt strips a cartridge from the magazine and rams it forward into the breech, before it hits the end the ignition system kicks in and fires the cartridge. By the time the projectile leaves the cartridge the latter would have locked into the breech, but in terms of recoil the gasses would be trying to push back a cartridge that is already travelling in the opposite direction as opposed to a static one.

Could be an overcomplication though, depends on calibre, mix and cartridge size.

Ooh ooh! We could make it like Batou's "standard issue big gun" from Ghost in the Shell :D

Image

It has a toggle action, just like the luger :)


ramses wrote:and as to the piston valve with the "captive" air, that was pretty much my contest entry, and it does work. Even though I lost


It was a very good effort, don't beat yourself up over it ;)
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Unread postAuthor: POLAND_SPUD » Wed Sep 23, 2009 5:37 am

@jsr
sounds cool but I doubt you could convince others to build it this way... the guidelines doesn't explicitly state that you can't use cartridges... well they don't even say that it has to be semi auto...

the design that rag mentioned in one of the threads could be useful here (though it's not needed) but cartridges don't offer any advantages here apart from differential recoil

for the same volume a launcher using cartridges will be heavier than a traditional launcher... even though it's not stated we can assume that this project aims at achieving the highest possible power mainly... so cartridges are seriously disadvantaged here

I am not saying that cartridges don't have any advantages but they would make more sense in a project that focuses on rate of fire...
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 23, 2009 7:08 am

POLAND_SPUD wrote:the design that rag mentioned in one of the threads could be useful here (though it's not needed) but cartridges don't offer any advantages here apart from differential recoil


I disagree:

I am not saying that cartridges don't have any advantages but they would make more sense in a project that focuses on rate of fire.


The specs say "and has a rate of fire of one round at least every 20 seconds." ;)

for the same volume a launcher using cartridges will be heavier than a traditional launcher...


The cartridges don't have to be in a magazine, they can be available loose like one would carry for a break barrel shotgun, in that case the firer only has to deal with the weight of one cartridge at a time - big advantage compared to the weight of an on-board fuelling system.

... even though it's not stated we can assume that this project aims at achieving the highest possible power mainly... so cartridges are seriously disadvantaged here


Assuming a locked breech, there should be no difference between a cartridge and a fixed chamber.

Oh come on, I just want to see brass fly! Pleeeeeease? Pretty please with icing on top?

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Unread postAuthor: inonickname » Wed Sep 23, 2009 7:11 am

To satisfy JSR, we could just feed the ammunition in ejected cartridges.
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Unread postAuthor: Ragnarok » Wed Sep 23, 2009 7:37 am

POLAND_SPUD wrote:the design that rag mentioned in one of the threads could be useful here (though it's not needed)

That's really more useful for smaller launchers that need to fire very fast. Not that it can't be used in larger launchers, but it's not necessarily the way to go about it.

jackssmirkingrevenge wrote:The specs say "and has a rate of fire of one round at least every 20 seconds."

That's not such a demanding rate of fire if you look at it. Not such of a challenge that you start needing to look at any particularly special options.

~~~~~

Anyway, in this case, more weight would not be a bad idea - if you're putting out a 5 ounce projectile out at 1600 fps (Moonbogg's aimed specs, if I recall the chat the other day), you'll need some fairly hefty mass in order to absorb that recoil.
Personally, I wouldn't make this launcher any less than about 15 kilos total weight, and even then the recoil will be very serious. (Although a muzzle brake might allow you to cut that slightly).
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