Search found 26179 matches

by jackssmirkingrevenge
Fri Dec 01, 2023 9:57 am
Forum: Off-Topic Hobbies
Topic: Buy on ebay
Replies: 23
Views: 116842

Re: Buy on ebay

The "eBay" in the title seems to make this post a bot-magnet :D
by jackssmirkingrevenge
Thu Nov 30, 2023 10:07 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29916

Re: Hybrid disk burst pressure effect on performance

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...
by jackssmirkingrevenge
Wed Nov 29, 2023 3:29 pm
Forum: Combustion Cannons
Topic: HGDT Guide
Replies: 5
Views: 4061

Re: HGDT Guide

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...
by jackssmirkingrevenge
Wed Nov 29, 2023 2:07 pm
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29916

Re: Hybrid disk burst pressure effect on performance

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...
by jackssmirkingrevenge
Wed Nov 29, 2023 1:48 pm
Forum: BB, Airsoft, and Pellet Guns
Topic: Crosman 1400 Pumpmaster 0.22"
Replies: 35
Views: 25665

Re: Crosman 1400 Pumpmaster 0.22"

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...
by jackssmirkingrevenge
Tue Nov 28, 2023 12:37 pm
Forum: BB, Airsoft, and Pellet Guns
Topic: Crosman 1400 Pumpmaster 0.22"
Replies: 35
Views: 25665

Re: Crosman 1400 Pumpmaster 0.22"

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...
by jackssmirkingrevenge
Tue Nov 28, 2023 12:35 pm
Forum: Combustion Cannons
Topic: HGDT Guide
Replies: 5
Views: 4061

Re: HGDT Guide

Do you have any specific questions? What are you trying to model exactly?
by jackssmirkingrevenge
Sat Nov 25, 2023 4:02 pm
Forum: General How-To & Discussion
Topic: Fly-K mortar - "captive piston" variation
Replies: 14
Views: 26582

Re: Fly-K mortar - "captive piston" variation



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
by jackssmirkingrevenge
Fri Nov 24, 2023 11:12 am
Forum: Hybrid Cannons
Topic: Hybrid geometry
Replies: 7
Views: 6324

Re: Hybrid geometry

My chamber walls are around .23" thick, so I should be able to run mixes considerably higher than 15 and remain in a safety margin. (Mathwise anyway) Given the materials and toolings you've shared previously I was hoping this would be the case ;) Another thought: have you experimented with an *inne...
by jackssmirkingrevenge
Fri Nov 24, 2023 10:34 am
Forum: Hybrid Cannons
Topic: Hybrid geometry
Replies: 7
Views: 6324

Re: Hybrid geometry

Moonbogg wrote:
Fri Nov 24, 2023 1:18 am
Now the OP can just focus on simplicity.
With say a 30 inch long barrel and 15x mix one can envisage sending a half inch round ball downrange at just over the speed of sound :D
hgdt.jpg
by jackssmirkingrevenge
Thu Nov 23, 2023 10:43 pm
Forum: Pneumatic Cannons
Topic: Valve reliability
Replies: 7
Views: 9488

Re: Valve reliability

A very interesting design! Also, to help it open, i had hollowed out the spool so the collar on the sprung rod impacts it to get it moving. Before that, the o-ring sticking friction at higher pressures was too high for the spring to move it. I can image that, the pressure causes the o-rings to expan...
by jackssmirkingrevenge
Thu Nov 23, 2023 10:28 pm
Forum: Hybrid Cannons
Topic: Hybrid geometry
Replies: 7
Views: 6324

Re: Hybrid geometry

An interesting question and I thought worth investigating, so I made the following modifications to the Mini Hybrid II : Blunt endcap insert: 20231123_211452.jpg Insert bore tapered: 20231123_214925.jpg I fired two shots each with both endcap variations, for each shot I used a 63cm long 0.177" barre...
by jackssmirkingrevenge
Mon Nov 20, 2023 9:48 am
Forum: Hybrid Cannons
Topic: Mini Hybrid II
Replies: 11
Views: 28322

Re: Mini Hybrid II

mark.f wrote:
Sun Nov 19, 2023 9:56 pm
That's a hell of a BB gun. :D
We have moved somewhat past "you'll shoot your eye out!" territory into something altogether more serious :twisted:
by jackssmirkingrevenge
Sun Nov 19, 2023 9:59 am
Forum: Pneumatic Cannons
Topic: Valve reliability
Replies: 7
Views: 9488

Re: Valve reliability

I had doused it with oil several times to prevent wear, and made sure there were no sharp edges on the ports, but apparently that is not enough. The other draw back was the higher the chamber pressure, the harder it became to open at the o-rings are pushed into the cylinder walls increasing frictio...
by jackssmirkingrevenge
Thu Nov 16, 2023 1:10 pm
Forum: Hybrid Cannons
Topic: Mini Hybrid II
Replies: 11
Views: 28322

Re: Mini Hybrid II

I made a 0.177" barrel attachment for this thing, at a 20x mix it was pushing 0.35 gram BBs to just over 1800 feet per second :D that's 39 ft lbs of energy! https://www.youtube.com/watch?v=23-DWhJ0-MA The same barrel hooked up directly to the air cartridge at 2500 psi yielded 1143 fps, still impress...