Search found 1593 matches

by Moonbogg
Thu Jul 09, 2020 2:36 pm
Forum: Combustion Cannons
Topic: Colinfurze makes a combustion repeater
Replies: 0
Views: 3

Colinfurze makes a combustion repeater

It looks awesome. Only question I have is how does he vent if before the next shot?

by Moonbogg
Wed Jul 01, 2020 10:24 pm
Forum: Ammo & Parts
Topic: Brass as the foundation of a projectile?
Replies: 4
Views: 172

Re: Brass as the foundation of a projectile?

It sounds like a good idea to me. At least worth trying for sure. It's always fun even if it doesn't work as hoped for.
by Moonbogg
Wed Jul 01, 2020 10:18 pm
Forum: BB, Airsoft, and Pellet Guns
Topic: Confused. Cylinder chamber to barrel ratio for compressed air.
Replies: 8
Views: 269

Re: Confused. Cylinder chamber to barrel ratio for compressed air.

Talking about both volume and pressure. For a determined Barrel to cylinder / chamber ratio. Without changing barrel volume. Just working on cylinder and pressures to volume. I could be wrong too, seen somewhere take 1 bar off regulated pressure gives actual reg pressure. In that case suppose adjus...
by Moonbogg
Wed Jul 01, 2020 2:28 pm
Forum: Combustion Cannons
Topic: Using Burnt Latke's fuel tool
Replies: 3
Views: 88

Re: Using Burnt Latke's fuel tool

I read spudblaster's hybrid fueling 101 which is stickied in the hybrid cannon forum. He told us how to do it, so I'll reiterate it here. I don't bother with any of this math myself because HGDT was thunk about so I don't have to do any thunking about fueling and I can just focus on my design. Here'...
by Moonbogg
Wed Jul 01, 2020 1:49 pm
Forum: BB, Airsoft, and Pellet Guns
Topic: Confused. Cylinder chamber to barrel ratio for compressed air.
Replies: 8
Views: 269

Re: Confused. Cylinder chamber to barrel ratio for compressed air.

It sounds like you are talking about chamber size when talking about volume. That's the volume of the container. People also talk about the volume of a gas, such as 5 cubic inches of gas at atmospheric pressure. So, if you have a big container and a small container, but the same volume of gas going ...
by Moonbogg
Tue Jun 30, 2020 6:17 pm
Forum: BB, Airsoft, and Pellet Guns
Topic: Confused. Cylinder chamber to barrel ratio for compressed air.
Replies: 8
Views: 269

Re: Confused. Cylinder chamber to barrel ratio for compressed air.

If you have the same air volume and the chamber is 1/3 the volume, the pressure will increase by 3x.

https://www.omnicalculator.com/physics/boyles-law
by Moonbogg
Thu Jun 18, 2020 12:03 am
Forum: Combustion Cannons
Topic: Multiple ignition points?
Replies: 3
Views: 161

Re: Multiple ignition points?

I wonder if the benefit of 2 gaps vs 1 is greater than the benefit of 3 vs 2. I'd imagine diminishing returns would be kicking in at 3 gaps. As you mentioned above, the variance in velocity from potato to potato is often very significant anyway. It might make any real benefit of additional gaps kind...
by Moonbogg
Mon Jun 15, 2020 11:23 pm
Forum: Combustion Cannons
Topic: Multiple ignition points?
Replies: 3
Views: 161

Re: Multiple ignition points?

I saw some chrony data that Latke did showing an average velocity with 2 sparks at about 360fps. With 3 sparks it was about 390fps. I haven't seen data between 1 spark and 2 sparks. The thread is around here somewhere, but it's old and I don't want to spend 30 minutes searching for it to dig it up. ...
by Moonbogg
Sat Jun 13, 2020 9:47 pm
Forum: Ammo & Parts
Topic: Ideas for biodegradable cannon-balls
Replies: 15
Views: 2619

Re: Ideas for biodegradable cannon-balls

Hey, I saw a post from a guy here who BAKED ammo out of flour and then dipped it in wax. I would love to bake the perfect biodegradable cannonball. Any idea how the heck you bake ammo out of flour? Mix in some eggs or what? My cannonballs would be huge (same diameter as soda cans) and probably take ...
by Moonbogg
Sat Jun 13, 2020 9:39 pm
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1477
Views: 89197

Re: Short question topic

I wonder if the shape of the B version could also have something to do with it. At least you can solve it by making up for it with more fuel and air. The A version is more like a burst disc configuration. I'd like to have two identical cannons, one using a burst disc and the other using a piston, an...
by Moonbogg
Sat Jun 13, 2020 8:08 pm
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1477
Views: 89197

Re: Short question topic

Based on the sketches the first thought that comes to mind is that you may not have enough chamber volume to move the piston and also the projectile. Maybe I'm missing something, but if I reduced the chamber volume of my piston cannon to be very tiny, then I'd expect most of the energy to go into mo...
by Moonbogg
Sat Jun 13, 2020 2:39 pm
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1477
Views: 89197

Re: Short question topic

I think I see what you are saying. The gas uses energy to move the piston, and once that work is done, that energy has been transferred and you can't get it back to do any work on the projectile. Would it be the same situation with a burst disc? It requires a lot of energy just to break the disc, bu...
by Moonbogg
Fri Jun 12, 2020 10:22 pm
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1477
Views: 89197

Re: Short question topic

I don't know what the percentage is. I think It depends on the opening pressure of the piston. Since the work is being done with pressurized gas to open the piston, as soon as it opens all of that working gas suddenly goes to work on the projectile and sends it into orbit. So, it may seem as though ...
by Moonbogg
Fri Jun 12, 2020 4:00 pm
Forum: Hybrid Cannons
Topic: Port size vs performance
Replies: 8
Views: 354

Re: Port size vs performance

Fantastic replies. Thanks for the interesting thought experiment, D_Hall. That gives me something to mentally chew on. I feel 1 3/8" is where it will probably end up for this one. An interesting thing I noticed is that giant (2 5/8" dia) potatoes break apart at 4X and I'm wondering if the 1" port is...
by Moonbogg
Thu Jun 11, 2020 6:43 pm
Forum: Hybrid Cannons
Topic: Port size vs performance
Replies: 8
Views: 354

Port size vs performance

Intuitively I want to make a port size the same diameter as the barrel for maximum flow. However, intuition often fails. HGDT predicted that performance would be basically the same with a 1" port vs a larger port for my last design, and sure enough, performance is just fine. It makes sense that the ...