While using a single o-ring as both a seat seal and a check valve for filling functioned as a concept, I noticed that sometimes while purging the air line it would not reseal immediately, resulting in lower pressure in the cartridge and inconsistent performance, so I've modified the design with a se...

If my gut is right, making the baffle shorter (increasing volume of the chamber that has the spark gap in it), will decrease performance (decrease the step function effect). According to the study that inspired hectmarr's other thread, peak pressure should increase, but for a smaller effective volu...

I made a second baffle that was both shorter and with a 1/8" orifice that looks something like this to scale: baffling2.png I then did some more testing again at 16x and using photo paper disks and 0.25g airsoft BBs as projectiles: 1) 1 disk no baffle - 1136 fps / 21 J 2) 1 disk baffle - 1851 fps / ...

pressurepiling.png Looking at this in more detail, the paper describes what is happening in a closed system, with a significant pressure peak happening in the secondary chamber much higher than what occurs in the first one. In our case the dynamic is a little different as we want the second chamber...

You need something to induce turbulence! Some experimentation was definitely in order, so I machined a Delrin cup to fit the chamber with a 1/4" orifice through the base: 20231206_213324.jpg baffling.png I fired a series of shots and the results were quite interesting. The first thing I did was rep...

This effect would be affected by the chamber's interior, however. The more bends, rough surfaces, and such, the faster the gases would go turbulet. With that said, VERA has a fair amount of equipment mounted internally and the construction (steel pipe) means a less-than-glass-smooth surface. By con...

Late to the thread here (and I've only read the first post) but one of the things I've seen with VERA is that the burst pressure doesn't really make much difference (at least, not on her). Why? Simple, really... Once the disk bursts and the gases start to move, everything becomes very turbulent. Wi...

The "eBay" in the title seems to make this post a bot-magnet

Essentially, if the flame front of a propane/air mix typically moves at X fps, what happens if that mix is in motion prior to ignition? The effects you mentioned haven't really been studied within the community to my knowledge, although there are surely more academic papers out there. One of the th...

I'm still not entirely sure about the mix(Nx) input It's shorthand for the pressure before firing. If your mix of fuel and air is pressurized to 150 psi, then that's approximately 10 times atmospheric pressure so your input value should be 10. For an unpressurized basic combustion cannon this value...

Am I off my mark? The way I understand it, in a pneumatic the pressure is more or less constant while in a hybrid it's a brief spike. If we have a disk on a chamber that bursts at 1000 psi, then by filling that chamber until the disk bursts there will be 1000 psi of air to push the projectile. With...

It looks good and I think it's an interesting adaptation. I'm not sure how a sliding breech works... Think of it like the Huben K1 whose magazine feed functions on a similar principle: https://i.imgur.com/ufIaLpr.gif The projectile is placed inline with the valve and the barrel for minimum loss and...

This 1400 has languished in my parts bin for some years now, I'm wondering if it could be a candidate for a much more radical project. Here is roughly the concept I have in mind: https://i.imgur.com/farDIxq.gif The "blow open" idea and trigger are preserved, but the chamber and valve are moved in li...

Do you have any specific questions? What are you trying to model exactly?

Something relevant to the original post, an animation I had made of the Russian 2B25 "silent" mortar that works on a principle similar to the Fly-K