Short question topic

[jackssmirkingrevenge]

I had a similar idea for a valveless, except using a mechanism like a Quick Disconnect air hose fitting to lock the projectile in place.

Something like that:

[Xamllew]

I had a similar idea for a valveless, except using a mechanism like a Quick Disconnect air hose fitting to lock the projectile in place.

Something like that:

Exactly. Did you ever get a working prototype built?

[jackssmirkingrevenge]

Yes, to a point:



It just need a lot of force to operate even with relatively low pressures.

You would definitely need some form of strong hammer to set it off. Since I was looking at blowback mechanisms, I did not proceed with it as too much hammer strength would make blowback impossible.

[jrrdw]

@JRRDW, could you explain what you mean by air getting around the projectile and slowing it down? What I had in mind was a barrel diameter that narrows by less than a millimeter, going from decently airtight, to requiring a few tamps with a ramrod to fully seat.

If the projectile is air tight from chambered to exiting the muzzle it removes the issue from the equation. Any less of a seal could leak the pressure of gasses used to launch the projectile.

[Xamllew]

@JRRDW, could you explain what you mean by air getting around the projectile and slowing it down? What I had in mind was a barrel diameter that narrows by less than a millimeter, going from decently airtight, to requiring a few tamps with a ramrod to fully seat.

If the projectile is air tight from chambered to exiting the muzzle it removes the issue from the equation. Any less of a seal could leak the pressure of gasses used to launch the projectile.

Ah, i see what you mean. My dimensions would ideally allow the projectile to slide down with little effort, but then require a force of maybe 10lbs to seat the projectile into the constricted section at the bottom.

[farcticox1]

For a spring powered airsoft would a short stroke large bore piston work as well as a smaller bore piston with a longer stroke if they had the same displacement volume ? I'm thinking the larger bore piston would need a heavier spring but would be more compact length wise.

[mrfoo]

Porting and piston form is going to be important to get air out of a short, squat, cylinder into a long, slender, barrel in a hurry. The big issue is, IMO, going to be changing the direction of the air, as such I'd probably go for a conical piston face mating to a conical cylinder end, with highly radiused and polished port(s). Which loses some, or all, of the advantage in terms of compactness.

[farcticox1]

Anybody know the bolt pull/cocking force required on a typical airsoft sniper rifle? trying to get an idea of spring strengths I may need for a 100mm stroke piston, I have read that one has a 95mm stroke but can't find any force required data.

[wyz2285]

Any one could tell me whats these holes on the baffle are for? Like why isn't the hole/cut mirrored? Wouldn't' it cause non uniform turbulence?

[hectmarr]

Problem: My hybrid works with butane and air at 6 bar. When the combustion chamber is cold, around 8 -10ºC, it costs a lot to fire. After the first shot, everything works perfect.
My explanation, I do not know if it is correct or not, is that at 6 bar, the butane from the stoichiometric mixture that enters the cold chamber, condenses and therefore fails. When the combustion chamber heats up a little, around 30ºC, it is always in the gas phase. Someone to give me your opinion?
Aggregate:
Butane is liquid in the tank at about 3 bar. I made the measurement with a manometer.

[jackssmirkingrevenge]

Any one could tell me whats these holes on the baffle are for? Like why isn't the hole/cut mirrored? Wouldn't' it cause non uniform turbulence?

My understanding is that the turbulence increases the effect. These ports are commonly known as "mouse holes" and introduce what is essentially an angled jet of gas into the path of the main flow, slowing it down further.

My explanation, I do not know if it is correct or not, is that at 6 bar, the butane from the stoichiometric mixture that enters the cold chamber, condenses and therefore fails. When the combustion chamber heats up a little, around 30ºC, it is always in the gas phase. Someone to give me your opinion?

Intuitively that seems to be the best explanation.

[hectmarr]

I was testing and definitely preheating just a little, (with a heater), the camera, the problem is solved. Maybe using propane, which is kept in the gas phase at higher pressure, avoid all that.

Speaking of turbulators, it is important to consider. This phenomenon is what explains, because in some tests I'm doing, even with small combustion chambers, about 15 or 20 cm3, the power of the shot increases considerably just by waiting about 15 or 20 seconds before taking the shot. And logically, gases mix better.

[hectmarr]

How much energy, (in percentage and approximately), is subtracted from the air powered by the combustion process, in a hybrid with valve to piston, to displace this piston? I mean, I imagine, that of all the energy available to fire the shot, to accelerate the projectile, a good part is "eaten" by having to overcome the mixing pressure, the piston. I imagine that it is a mechanical work, an area, a small path, and an opposing force, and that the only source of energy at that moment is for high pressure inside the combustion chamber, at the moment of the explosion . Can someone clarify this point for me?
The question comes from seeing the ability to pierce targets drop, between a weapon without a valve, and the same weapon, (and the same pressure, and ammunition), with a piston valve to open when shooting, things I'm testing.

Variación fuerzas en híbrido con pistón y sin pistón.png (14.52 KiB) Viewed 29713 times

[Moonbogg]

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 you are "wasting" work potential to open the piston, but I see it as increasing "work density" where more work can be done in a shorter amount of time with a high-pressure burst. It takes a lot of the gas's energy to move the piston, but since the gas behaves like a spring, all of that energy springs into the projectile once the piston gets the hell out of the way. That's how I see it. Maybe someone more scientific with some actual knowledges can help more.

[hectmarr]

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 you are "wasting" work potential to open the piston, but I see it as increasing "work density" where more work can be done in a shorter amount of time with a high-pressure burst. It takes a lot of the gas's energy to move the piston, but since the gas behaves like a spring, all of that energy springs into the projectile once the piston gets the hell out of the way. That's how I see it. Maybe someone more scientific with some actual knowledges can help more.

I understand your point of view. When the piston opens at more pressure, it expends more energy but there is more energy available because the combustion chamber has more pressure, and vice versa. However, I think that the energy invested in opening the transfer, when the piston moves, does not recover or a very small percentage recovers. Thanks for your opinion.