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by D_Hall
Thu Mar 28, 2024 12:17 am
Forum: Hybrid Cannons
Topic: Hybrid velocity
Replies: 10
Views: 622

Re: Hybrid velocity

Yes, H and O are great. That's why you see 'em used in rockets. For bonus points, run it just a bit fuel rich and you get even lower molecular weight without much loss in temperature. And yes, that's why rockets run such. The same physics apply! That said, running H/O in a gun at anything that resem...
by D_Hall
Tue Mar 26, 2024 9:04 pm
Forum: Hybrid Cannons
Topic: Hybrid velocity
Replies: 10
Views: 622

Re: Hybrid velocity

What are methods of passing beyond the local SOS? The previously mentioned exploitation of Maxwell-Boltzmann distributions. Highly inefficient and has it's own limitations. Not useful for much more than braggin' rights. I imagine things like raising temperature beyond that of standard combustion or...
by D_Hall
Sun Mar 24, 2024 7:43 pm
Forum: Hybrid Cannons
Topic: Hybrid velocity
Replies: 10
Views: 622

Re: Hybrid velocity

A few thoughts in no particular order.... 1 - Post-combustion chemistry absolutely matters. It can drastically alter the local sonic velocity. 2 - Traditional powder-based guns can go much faster than OP's listed 5200 ft/s. I've personal experience with a gun that runs at 8,900 ft/s. 3 - I'm a bit b...
by D_Hall
Sun Jan 28, 2024 2:00 pm
Forum: SpudFiles Discussion
Topic: GGDT and HGDT
Replies: 22
Views: 31700

Re: GGDT and HGDT

Jack got it right.
by D_Hall
Sun Jan 21, 2024 7:26 pm
Forum: SpudFiles Discussion
Topic: GGDT and HGDT
Replies: 22
Views: 31700

Re: GGDT and HGDT

I didn't keep anything, but if you've a specific question I'm likely to be able to answer it.
by D_Hall
Sun Jan 14, 2024 2:03 pm
Forum: Pneumatic Cannons
Topic: Where to download GGDT
Replies: 3
Views: 7394

Re: Where to download GGDT

I don't remember where it's stashed, but it's actually on this site somewhere....
by D_Hall
Thu Jan 11, 2024 7:11 pm
Forum: Off-Topic Hobbies
Topic: My current hobby: Cowboy Action Shooting
Replies: 24
Views: 86606

Re: My current hobby: Cowboy Action Shooting

And as a minor brag, I set a new personal best last weekend....



...Still not going to win any championships, but I felt really good about that run.
by D_Hall
Sun Dec 17, 2023 6:09 pm
Forum: Combustion Cannons
Topic: Potato cannon not igniting
Replies: 3
Views: 6288

Re: Potato cannon not igniting

As hinted at in the previous post.... The most likely cause is incorrect fuel/air ratio. Unfortunately, this is not an easy thing to measure with a "spray and pray" potato gun. First things first? Ditch the hair spray (that is an affront to the potato gun gods!), and find a way to MEASURE how much b...
by D_Hall
Mon Dec 11, 2023 9:29 pm
Forum: Combustion Cannons
Topic: HGDT Guide
Replies: 5
Views: 4058

Re: HGDT Guide

jackssmirkingrevenge wrote:
Wed Nov 29, 2023 3:29 pm
I believe a stoichiometric mix ratio is assumed depending on the chosen fuel.
Correct. I am NOT going to loop in PEP or any similar combustion codes!
by D_Hall
Fri Dec 08, 2023 12:31 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29858

Re: Hybrid disk burst pressure effect on performance

That's enough experimentation for this session but I would also like to try cutting down the baffle to make the "second chamber" smaller to see if that makes a difference, I wonder if it will increase or reduce peak pressure at the disk. If my gut is right, making the baffle shorter (increasing vol...
by D_Hall
Fri Dec 08, 2023 12:28 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29858

Re: Hybrid disk burst pressure effect on performance

A mesh screen would kick up turbulence but also suck up a lot of heat. We have discussed before if running the chamber fan during firing might increase the burn speed. Way back when I measured burn speed in a closed chamber at 1x with/without the fan running and with one or three sparks gaps. There...
by D_Hall
Wed Dec 06, 2023 8:28 pm
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29858

Re: Hybrid disk burst pressure effect on performance

My gut says we're on to something.... You need something to induce turbulence!
by D_Hall
Wed Dec 06, 2023 12:01 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29858

Re: Hybrid disk burst pressure effect on performance

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...
by D_Hall
Sat Dec 02, 2023 2:53 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29858

Re: Hybrid disk burst pressure effect on performance

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. Wit...
by D_Hall
Fri Oct 27, 2023 2:51 pm
Forum: Combustion Cannons
Topic: Ideal C:B ratio?
Replies: 3
Views: 3413

Re: Ideal C:B ratio?

The 0.8:1 ratio comes from burntlatke's testing where chamber volume was held constant and barrel volume was changed, which effectively found the longest barrel length that could efficiently use a certain chamber size.. It is worth noting, however, that latke was using potatoes for projectiles and ...