I've been quietly following this thread for a while, and I'd like to congratulate you for pursuing the project this far. There aren't many hybrids this big around, and they don't tend to get fired very often, so it's a rare treat to see one in action. What were the parameters for this shot? Specific...

This is actually a pretty interesting question, now that I'm thinking about it. I'll bet that Jimmy will have a more satisfactory answer. The listed heat of formation for acetylene (+225 kJ/mol) suggests it to be energetically favourable for acetylene to decompose into carbon and dihydrogen, which i...

Regarding the use of a heavier / higher friction potato slug: using a propane/air mixture starting at atmospheric pressure, the maximum theoretical pressure is about 120psi. This would be, roughly, the pressure generated in a sealed, perfectly insulated chamber with no significant contribution from ...

Generally speaking, piston weight should be chosen based on the desired pressure profile - a heavier piston will travel slower and tend to reduce the amount by which the pressure spikes above the disk rupture pressure. Varying piston mass makes possible a great deal of tuning, for example to try to ...

...14.4g is nothing for a 0.76" bore! Well, it's about the largest mass that this gun can get up to decent velocity. Projectiles between 5g and 10g will be more common when it's operating as a single stage gun. Pistons for the LGG would be heavier though, between 20g and 60g depending on the other ...

Let me just come out and say this: I hate multiple spark because it doesn't work! Current flows through the path of least resistance, and air had quite high resistance, even with the fuel in there, so if your electrodes are not exactly as close to each other (close to impossible), then there is a p...

The accuracy would still be expected to be 0.25% of the full scale at any pressure, unless the manufacturer explicitly specified otherwise. Most manometric systems use two gauges because of the following problem: The air pressure is about 20 times the fuel pressure, and you don't want to go past 3/4...

1. Apart from concern about the field gradient inducing breakdown in the surrounding air and insulation (which would be a major concern at 19MV), the diameter of the wire has nothing to do with the voltage. I get the feeling that you may be conflating the voltage difference between the wire and the ...

I recommend against a ball valve directly behind the union, as it may fire when the valve is not fully open. This will reduce performance, and could introduce large shot-to-shot variability. Your other idea is better. Any burst disk system is not ideal for use in games. Something using a cam lock fi...

Simple and high performance tend to be enemies. If you can accept a small delay (on the order of tens to hundreds of milliseconds, depending on flow rate), you could simply open a ball valve that rapidly fills the chamber until the burst disc ruptures. This could also be automatically controlled to ...

Propane air would definitely be adequate for the first stage of a LGG, but there are two project branches at play here, and one of them is the eventual development of an oxy/hydrogen CLGG. It seemed more convenient to incorporate them into one build, considering that the scales were the same, and th...

MrCrowley, those are the same parameters I used when I got the rats nest. Which version are you running? I have v0.5.4. Jrrdw, the video was just thrown together in WMM last night. I don't have my own computer set up at the moment, and didn't see the point in going to any trouble making a video for ...

I don't live in an apartment, and no one outside of my house can hear anything noticeable during these tests, as they're done in a basement. Moving everything outside is just too much trouble, especially on systems that aren't complete yet. MrCrowley: how did you simulate that on HGDT? I get one of ...

Stage1 is my first foray into the development of a combustion light gas gun, and has several design features not seen before on Spudfiles. First, the specifications, interspersed with the relevant pictures: Chamber : 1.525" ID x 3.5" long, 1.5" long taper from 1.525" to 0.800". 2024-T651 aluminum wi...

What, no video? :P Good to see you got this working, especially considering the awkward ignition placement. I've used regular 600 WOG ball valves on hybrids up to 10X air/propane with no major problems, so you should be fine here. As regards your question on the barrel: J-B Weld claims a tensile lap...