hybrid cartridge protoype without burst disk

[myinisjap]

you were right about it not giving an air tight seal it didn't really develop the leak until I tested it at 100psi. Going to try compressing the projectile that I cast into the cartridge to see if I might be able to seal up the leak. But that will have to wait till my next day off.

[jackssmirkingrevenge]

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

Looks good, those are going to be some pretty big cartridges... anti-tank rifle then

it didn't really develop the leak until I tested it at 100psi

Most launchers don't leak until you test them

As I said, casting is not the best of ideas - swaging on the other hand works.

[jackssmirkingrevenge]

Some progress, and possibly the smallest hybrid shot ever:

[youtube][/youtube]

This is the only shot I managed, fuelling is extremely fiddly. However, the o-ring detent setup held in a threaded fitting worked perfectly in terms of "valveless" filling and firing, and since it was made out of delrin cutting the threads was no big deal.

In this regard, I'm going to scale it up to 0.22", watch this space

Here's the setup, I machined a PVC inlet for the fill rig in order to reduce dead (non cartridge) volume and make it easier to force the projectile to seal against the detent:

[LeMaudit]

Nice work! Love the tiny cartridge! 8)

[Gun Freak]

Wow, that is tiny. Cool, what is this like your 50th hybrid or so, lol

[JDP12]

Hang on, I'm confused. maybe its because its 0127 in the morning, but bear with me. The whole idea with the pin inserts is for the fill rig correct, and the cartridge still has a threaded front for the o-ring holder? or does the cartridge have a pin holder method as well?

[jackssmirkingrevenge]

Nice work! Love the tiny cartridge! 8)

Cute, isn't it one step closer to the hybrid pengun

Hang on, I'm confused. maybe its because its 0127 in the morning, but bear with me. The whole idea with the pin inserts is for the fill rig correct, and the cartridge still has a threaded front for the o-ring holder? or does the cartridge have a pin holder method as well?

Yes, the steel pin is what holds the fill rig closed. The cartridge has an o-ring detent held in place with a threaded fitting that also serves as a "fill valve".

Scaled it up and been fiddling with it all morning, but no luck, the detent is impossible to adjust! It's either too weak and pops the projectile as soon as you depressurise the fill rig, or too strong and doesn't pop even with a 25x mix burning behind it.

[POLAND_SPUD]

hmm maybe you need a different oring ?? or the oring holder should be modified so orings wouldn't be supported from the sides and can expand when needed

[mark.f]

Scaled it up and been fiddling with it all morning, but no luck, the detent is impossible to adjust! It's either too weak and pops the projectile as soon as you depressurise the fill rig, or too strong and doesn't pop even with a 25x mix burning behind it.

Guess it's too late to suggest the more controllable burst disks again, right? Although with such a small design any device to hold back a specific amount of pressure with be fiddly at best.

Good work and nice usage of your new machinery.

[jackssmirkingrevenge]

hmm maybe you need a different oring ?? or the oring holder should be modified so orings wouldn't be supported from the sides and can expand when needed

I've used both 6mm ID and 5mm ID o-rings and tons of combinations of tightness and mixes, but didn't get a single successful shot - either I depressurise the fill rig and find the projectile has come out of the cartridge, or the ignitor goes click-click-click and nada, but the cartridge is warm and full of smoke.

Guess it's too late to suggest the more controllable burst disks again, right?

Alternating between those and a piston design in my head right now to be honest, the lformer has better performance but would require a separate fill valve, a piston is more convenient in some ways.

[JDP12]

I think the coaxial piston idea is probably the easiest one to go with, very little troubles manufacturing, dont have to worry about detent pressure, et cetera. Granted they may be a bit more bulky, but at some point you have to decide if the small size is worth the extreme hassle of detent cartridges.

[POLAND_SPUD]

I've used both 6mm ID and 5mm ID o-rings and tons of combinations of tightness and mixes, but didn't get a single successful shot - either I depressurise the fill rig and find the projectile has come out of the cartridge, or the ignitor goes click-click-click and nada, but the cartridge is warm and full of smoke.

well the previous one worked fine, right ? so I guess you can spend a few extra minutes to work this out rather than throw it away

I've used both 6mm ID and 5mm ID o-rings

ohh you didn't get what I meant... I meant that orings probably need to have room around them to expand outward

[jackssmirkingrevenge]

well the previous one worked fine, right?

Once

so I guess you can spend a few extra minutes to work this out rather than throw it away

I literally spent the whole morning fiddling with it, didn't get the right combination.

[Crna Legija]

how about a system they use to hold bits in die grinders/mills.

hope you get what im on about

[jackssmirkingrevenge]

Collets.

How are you proposing the system be applied though?