This is one of the few examples I remember of a publicly available paper from Utron's contracted government research project for a "Combustion Light Gas Gun" (CLGG) - A.K.A. a badass hybrid that many strived here to get close to. Full paper here: https://apps.dtic.mil/sti/pdfs/ADA462130.pdf There i...

I looked at the GGDT program and it doesn't appear to have an option to calculate the maximum range in which it will be able to fire which is in my opinion the whole point of the software.. The point of the program is to have an idea of what your muzzle velocity will be. As for maximum range, that ...

Probably the quickest/easiest hand calcs you can do for potato gun prediction.... EndPressure = StartPressure * ChamberVolume / (ChamberVolume + BarrelVolume) MuzzleEnergy = (StartPressure + EndPressure) / 2 * BarrelLength * PI/4 * BarrelBoreDiameter^2 MuzzleVelocity = sqrt (2 * MuzzleEnergy / Proje...

Setup wasn't anything fancy.

Canon T-6 (about a five year old consumer level DSLR).

Comet pic was taken with a 70-300 zoom lens at...maybe 100 mm.

Milkyway pic was taken with a fixed 50 mm lens.

Decent tripod.

Not star trackers or telescopes in the normal sense of the word.

...I'm still pretty pleased with these two pics I took tonight.

I'm sitting here looking at a piece of 38 special brass. It just happens to be on my desk (yes, really). And I'm thinking to myself, "Self, this might make a good projectile." More to the point, I could see epoxying a nail in the primer pocket to make a dart. But a dart that is reasonably cheap/easy...

Some more thoughts on the thought experiment.... It assumes constant density, but this is obviously incorrect. But what DOES density do? In the first moments after the valve opens, not much. Constant density probably isn't a bad approximation. But as the projectile accelerates we know that pressure ...

The purist in me loves the idea of a port that is actually larger than the bore, with the breech tapering down such that flow into the bore is smoooooth and maximized. But yeah, the realist in me realizes that for the vast majority of cases this is beyond overkill. Hmmm... Let's see if I can come up...

Gun shot great. Had a lot of fun. Was stunned to NOT have the oldest gun at the range. One of the guys was shooting a .40-70 Trapdoor!

For all you folks who don't know old guns (not that I'm an expert)... Custard's men were using Trapdoors at Little Big Horn.

Turns out that the same guys who run the Cowboy Shoots also do what they refer to as BAM shoots.... Bolt Action Military. Basically the idea is to use a bolt action military rifle in as-issued condition that dates to 1945 or earlier. It also turns out that my Mom once bought an 1895 Mauser on a whim...

D_Hall, do you have any of the old documentation that went along with these? Or perhaps you or someone else is willing to help create some? Simple things about usage, running as an admin, the files that may need to be added, etc. I can certainly help here but don't want to reinvent the wheel if unn...

KannonKing wrote: ↑

Sat Apr 25, 2020 10:46 am

"pure oxygen" and fuel? Maybe you noticed the vacuum pump hidden in the battery box that evacuates the chamber before filling it with "pure oxygen and fuel".

If you're pulling a vacuum before injection, what *else* would you be using?

Yes, I found this topic a couple years late and it took me a bit to digest it.... ...But I don't think there's much to the "piling" phenom. It allows you to boost pressure, yes, but for a significantly smaller available volume in the combustion chamber. The result would be higher pressures, but decr...

[nevermind... hmmm... how does one delete a post with the new forum software?]

You're not going to get much lower friction than teflon seals, but they can still be a bear to turn. Ball valves simply aren't designed for quick/easy motion.