Expansion Chamber for MiniMag [Archive] - Automags.Org Online Forums

93civiccpe

03-31-2005, 12:47 PM

Hey,
Just about any screw in expansion chamber will work on a mag, you just need the vertical ASA adapter (or 15 degree adapter if you want it angled) to hook it to the rail. This will replace the foregrip on your rail. The ASA adapter will attach just like that foregrip does, just a screw that goes from the inside of the rail into the threads of the adapter. Then you can screw either an expansion chamber or an air-through grip to that ASA adapter. I have heard people like the multi-chamber expansion chambers for helping prevent the liquid co2 from getting into the gun. Personally I have never used co2 except for in a spyder, which i didn't care if it sucked up a little liquid co2. I would advise against using co2 in a mag, even with a classic valve because even though I've seen people have a lot of success with it, I personally would just invest in HPA. If you do want to stick with co2, I would suggest a good multi-chamber expansion chamber, a remote system, and putting an anti-siphon tube in the co2 tank. If you are thinking of upgrading to a better valve in the future you should probably just upgrade to HPA.

I hope this helps, if anyone actually runs co2 on their mags please chime in to help him. I am familiar with a local's setup on a classic mag with expansion & remote using co2, but I don't have a lot of experience with it so I'm sure someone else would have some better information for him.

PumpPlayer

03-31-2005, 02:10 PM

Co2 on mags (classic valve only) is perfectly fine. You just have to remember that you're not dealing with an ideal gas (remember your chemistry lessons here) and you need to take steps accordingly.

Obviously we want to keep liquid out off the valve of any marker simply for shot consistency reasons, but when dealing with a regulator (like on a 'mag), we want to do whatever we can to ensure that the pressure drop associated with passing the gas through the valve won't put it into the saturated region. (making it 'wet' - containing droplets of liquid) As you drop the pressure of a gas, its temperature drops as well and you run the risk of entering the saturated region where the gas will condense. Incidentally, all gas coming from your CO2 tank is saturated vapor. It will condense almost immediately when you drop the pressure. As RT's, X-valves, E-mags, etc have a much faster recharge than the standard 'mag valve, the rapid pressure change will freeze your seals, causing them to crack and leak.

The only way to ensure that liquid does not enter your marker is to push the CO2 vapor into the superheated region. This is done by adding energy to the gas so that when the pressure drops, it remains in its gaseous state.

An expansion chamber drops the pressure (and thus the temperature) using a small orifice (or multi-stages of many orifices). Because the 'wet' saturated mixture will then be at a lower temperature than ambient, it will pick up heat from the surrounding air through conduction through the chamber. The main disadvantage of expansion chambers is that orifices only drop the pressure when there is flow through it. When the marker is not firing (no flow) - the pressure, temperature and mixture "quality" will equalize throughout the marker (destroying anything the expansion chamber would do in the first place). An expansion chamber alone only works during rapid-fire at a speed that the heat conduction can keep up with. Too fast and you'll freeze up, too slow and the expansion chamber doesn't do anything.

If you want to use an expansion chamber, at least put a check valve between the chamber and the 'mag's valve. (the closer to the chamber, the better) All that will do is prevent the equalization of mixture "quality" and aid in keeping liquid out when you're not rapid-firing. You can also help yourself by using a longer line between the x-chamber outlet and the 'mag valve. Which is why you see markers from the old days with big 'ol loops of hose leading to the valve - it helps heat the CO2 vapor and it contains a larger volume of superheated vapor.

Much better than an expansion chamber would be an in-line regulator. Why? Well, like the expansion chamber, the in-line reg drops the pressure (and thus the temperature) allowing ambient conditions to heat the mixture, increasing the enthalpy and pushing it into the superheated region (got all that?).

The difference is that a regulator will drop the pressure even with no flow. It acts as a check valve of sorts and prevents the mixture in the tank from 'wetting' the gas in the line. Something like the Bob Long Torpedo or Palmer's stabilizer will drop the pressure/temperature of the CO2, allowing it to heat back up in the line to ambient temperature. This will push it into the superheated region, preventing it from condensing as it passes through the mag's valve. Unlike an expansion chamber, a regulator will give you first-shot consistency rather than relying on rapid-fire to equalize. It's also a controlled pressure drop and will be more consistent than an expansion chamber. As an orifice device, an expansion chamber will function differently at different flow rates so your velocity will fluctuate depending upon how fast you're firing - a regulator won't do that.

The ideal set-up for CO2 would be a tank directly into an in-line regulator (palmer's female stabilizer as an example), into a gas-though foregrip (acts as an air volume chamber) and then having at least 6" of line between the vert. ASA and the 'mag valve.

That's going to give you the BEST performance on CO2 and you'll likely never freeze up or experience shoot-down. Is it expensive? Yeah - you're looking at less than $100 for a regulator, $10 for a foregrip, maybe $10 for a vert. ASA, $10 for lines/fittings and whatever you use to mount the regulator. --> For all that, most people would just as soon get an HPA tank.

Keep in mind that while a $20 expansion chamber will help a little bit in rapid-fire conditions, your first shot or two will still be erratic. Only a regulator can solve that problem. If you do decide to go with the expansion chamber, I'd recommend an ANS or I believe Benchmark used to make them - I've had good experiences with both. Good luck!