Search found 1886 matches

by D_Hall
Fri May 28, 2021 8:33 pm
Forum: Off-Topic Hobbies
Topic: Two Italian WW2 helmets found
Replies: 5
Views: 560

Re: Two Italian WW2 helmets found

I think you're lucky to live in a location with history. I'd love to do stuff like that but.... Well, there isn't really anything like that around here. Nobody lived here until WWII (and even then it wasn't a battleground).
by D_Hall
Fri May 28, 2021 1:06 am
Forum: Hybrid Cannons
Topic: Any official studies of Hybrid Cannons?
Replies: 8
Views: 1259

Re: Any official studies of Hybrid Cannons?

I remember a paper that went with that presentation, but now that I think about it.... That may not have been public release. Not sure.
by D_Hall
Sat May 22, 2021 4:46 pm
Forum: Hybrid Cannons
Topic: Any official studies of Hybrid Cannons?
Replies: 8
Views: 1259

Re: Any official studies of Hybrid Cannons?

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...
by D_Hall
Sun Nov 08, 2020 3:58 pm
Forum: Pneumatic Cannons
Topic: PVC Primer/Glue says DO NOT TEST WITH AIR
Replies: 8
Views: 1959

Re: PVC Primer/Glue says DO NOT TEST WITH AIR

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 ...
by D_Hall
Sun Jul 26, 2020 1:30 am
Forum: Pneumatic Cannons
Topic: Calculations related to pneumatic cannon.
Replies: 9
Views: 4649

Re: Calculations related to pneumatic cannon.

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...
by D_Hall
Mon Jul 20, 2020 11:09 am
Forum: Off-Topic Hobbies
Topic: I'm not photographer but....
Replies: 4
Views: 2495

Re: I'm not photographer but....

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.
by D_Hall
Mon Jul 20, 2020 12:53 am
Forum: Off-Topic Hobbies
Topic: I'm not photographer but....
Replies: 4
Views: 2495

I'm not photographer but....

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

Image

Image
by D_Hall
Wed Jul 01, 2020 5:50 pm
Forum: Ammo & Parts
Topic: Brass as the foundation of a projectile?
Replies: 6
Views: 2236

Brass as the foundation of a projectile?

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...
by D_Hall
Mon Jun 15, 2020 5:17 pm
Forum: Hybrid Cannons
Topic: Port size vs performance
Replies: 8
Views: 3272

Re: Port size vs performance

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 ...
by D_Hall
Fri Jun 12, 2020 2:36 pm
Forum: Hybrid Cannons
Topic: Port size vs performance
Replies: 8
Views: 3272

Re: Port size vs performance

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...
by D_Hall
Sat May 30, 2020 5:26 pm
Forum: Off-Topic Hobbies
Topic: My current hobby: Cowboy Action Shooting
Replies: 12
Views: 5975

Re: My current hobby: Cowboy Action Shooting

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.
by D_Hall
Sat May 30, 2020 1:25 am
Forum: Off-Topic Hobbies
Topic: My current hobby: Cowboy Action Shooting
Replies: 12
Views: 5975

Re: My current hobby: Cowboy Action Shooting

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...
by D_Hall
Sat May 02, 2020 10:01 pm
Forum: SpudFiles Discussion
Topic: GGDT and HGDT
Replies: 17
Views: 8734

Re: GGDT and HGDT

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...
by D_Hall
Mon Apr 27, 2020 12:48 pm
Forum: Combustion Cannons
Topic: New member... my baby, Big Red
Replies: 15
Views: 5114

Re: New member... my baby, Big Red

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?
by D_Hall
Fri Mar 06, 2020 4:29 pm
Forum: Miniature Guns
Topic: Dual Camera System to enhance combustion weapons.
Replies: 13
Views: 6132

Re: Dual Camera System to enhance combustion weapons.

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...