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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 » Sat Sep 24, 2011 9:53 am

You need some new material

:? Damn I am getting old

Better to add one time complexity to the fill rig than complicate every cartridge, this is how I see it:
Me approves


soo when are we going to see some flying brass ?
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Unread postAuthor: al-xg » Sat Sep 24, 2011 11:03 am

I feel I'm missing something on that last quick exhaust fill rig sketch.

Is there another valve involved not represented?
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 24, 2011 11:19 am

al-xg wrote:Weren't you meant to be venting the filling chamber on disconnecting the schrader ? :?


Shock pump, independent schrader opening and disconnection.

You should use some sort of quick release plug, or even just an o-ringed threaded cap.


Yep, there are simpler ways of going about it, most of which involve turning all or part of the rig into a projectile :D

soo when are we going to see some flying brass ?


Not tonight, there's a kilo of prime ribeye and 8 pack of finest epoxyland beer in the fridge that suggests I will be putting cartridges on hold for today ;)

I feel I'm missing something on that last quick exhaust fill rig sketch.

Is there another valve involved not represented?


You're perfectly right, I was still thinking air spring pop-off when I drew that, and to work it would require a separate schrader. The piston would be air tight, you fill the space behind it to just enough pressure to resist the mix pressure you intend to achieve, fill the main chamber from a separate valve and it automatically pops when ready.

An actual exhaust valve as described earlied might look something like this:
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Unread postAuthor: Labtecpower » Sat Sep 24, 2011 1:46 pm

Not tonight, there's a kilo of prime ribeye and 8 pack of finest epoxyland beer in the fridge that suggests I will be putting cartridges on hold for today :wink:


Makes fine targets when empty :D
You'd better speed up, i'm also designing a full auto now :wink:
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 25, 2011 1:53 am

Labtecpower wrote:Makes fine targets when empty :D


Can't use local ones, it would give away my location :)

You'd better speed up, i'm also designing a full auto now :wink:


Damn! *machines*

:P :D
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Unread postAuthor: HunterT » Sun Sep 25, 2011 4:32 am

jackssmirkingrevenge wrote:
Labtecpower wrote:Makes fine targets when empty :D


Can't use local ones, it would give away my location :)



Yeah, but we don't know what Epoxyland beer looks like.
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Unread postAuthor: Labtecpower » Sun Sep 25, 2011 5:11 am

Can't use local ones, it would give away my location :)


Doesn't matter to me, I already know it :D
You can give them a layer of masking tape.

Damn! *machines*


The design I posted will cost me about 10 euro's to make 5 pieces, not too expensive I think :P

At school I asked for the largest hand taps, and they go up to M24, so I won't have to use a very small bore :)

Yeah, but we don't know what Epoxyland beer looks like.


Google translator can read the text on it :wink:
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Unread postAuthor: myinisjap » Tue Sep 27, 2011 2:05 am

Read through all 37 pages of posts and wondered why I didn't see anyone suggest casting/pressing in the projectile. I was thinking something similar to an actual bullet. I will put up a drawing of what I am talking about tomorrow.
questions only testing would answer
At what psi will the projectile try to separate from the casing?
Would the friction of the projectile being cast in place provide a good seal?
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Unread postAuthor: Crna Legija » Tue Sep 27, 2011 2:38 am

myinisjap wrote:.
questions only testing would answer
At what psi will the projectile try to separate from the casing?


That and the time it would take to cast ammo into it. Also a cast bullet probably wont do much damage, if it was lead the heat would melt most seals, epoxy would takes to long to cure and would stick to everything and is expensive.

myinisjap wrote:Would the friction of the projectile being cast in place provide a good seal?


it wont be air tight.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 27, 2011 3:05 am

myinisjap wrote:Read through all 37 pages of posts and wondered why I didn't see anyone suggest casting/pressing in the projectile.


If you look atthis post it's pretty much what I did, but the projectile was swaged as opposed to being cast, putting a 4.5mm BB in a 4mm hole.

Image

it wont be air tight.


When swaged it held pressure surprisingly well:

Image

My only objection to this was the fact that as you're deforming the projectile, at best it would be inaccurate, at worst it could actually jam in the barrel.

It might work using pellets as opposed to BBs, but they would have to be loaded from behind.

Also, at 5x the combustion was enough to dislodge the projectile, suggesting that at higher mixes this relatively low "pop off" pressure would not allow the full power potential to be achieved.
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Unread postAuthor: myinisjap » Tue Sep 27, 2011 6:35 am

i was thinking this casting this type of ammo
Image

I am going to try and stop by the hardware store tomorrow to pick up some fittings, to test whether or not the design will hold pressure. And if it does how much it will hold.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 27, 2011 6:54 am

I've tried that type of pellet, hopelessly inaccurate from a serious air rifle and a bit of a gimmick. Here's a review that agrees with me.

Casting as opposed to swaging is likely to result in a much lower pop-off pressure, especially as the tendency is for the casting to shrink slightly as it cools.
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Unread postAuthor: POLAND_SPUD » Tue Sep 27, 2011 9:08 am

If you look at this post it's pretty much what I did, but the projectile was swaged as opposed to being cast, putting a 4.5mm BB in a 4mm hole.
I guess you could have designed a better 'detent' (or whatever you want to call it) for it

Was the tubing crimped ? I have no idea what kept the BB in place

I imagine that using a pipe cutter would be a good method to uniformly reduce the ID of the tube
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 27, 2011 10:48 am

POLAND_SPUD wrote:I guess you could have designed a better 'detent' (or whatever you want to call it) for it


If you're using lead only, then jamming it in place is really the only way to hold it, there's going to be some deformation on the way.

Was the tubing crimped ? I have no idea what kept the BB in place


No, it was simply a 4.5mm projectile jammed forcefully into a 4mm tube.

I imagine that using a pipe cutter would be a good method to uniformly reduce the ID of the tube


Either way you're going to squeeze the projectile.

I suppose a diabolo shaped pellet would act the same way as a squeeze bore shell and retain its aerodynamic characteristics if diameter reduces evenly.

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Unread postAuthor: Labtecpower » Tue Sep 27, 2011 12:23 pm

I started working on a prototype today, otherwise I will just keep dreaming and designing, and that won't get me a working gun :D

Turned the backplug out of some red PVC, on some a very nice "mini" lathe.
(Emco maximat super 11) it works very nice, and the finish is very smooth, opposed to the lathe I normally work on.

Image

Inventor drawing for the plug;

Image

Also bought a pipe for extra building stimulation :)

Image

23mm ID 27 mm OD aluminium pipe. I think it's plenty strong, as it is being used for construction purposes. (scaffolds is the right word? :P)
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