Sealing the magazine will improve efficiency, but it is not required. Still a good idea if you can do it, though.
Carl, Do you have a source/part # for that Tee fitting? I have not been able to find one locally. The closest i came was 1/4 OD compression on the ends with 1/8 NPT on the sides.
My local OSH carries T fittings suitable for a bb-caliber cannon. For larger ones, you'll need a different part. I'll ask my shopmaster where he got his.
The more I think about it the Arizona is really a single barreled, scaled down Indiana. Shouldn't the acumulator be lower pressure than the rest of the system? Shouldn't the poppet activating the MPA-3 be a MAV-3 rather than a MAV-2?
The answers to your questions are 0) short of. 1) sometimes. 2) yes. Yes, the Arizona is a scaled-down Indiana. However, the Arizona was developed first, so it is technically proper to say the Indiana is a scaled-up Arizona cannon. For actuation, the important part is that there is enough force to open the valve. The important thing here is the ratio of the buna-ball valve's cross-sectional area (or MJV valve's cross-sectional area) to the actuator's cross-sectional area. If the actuator has more area than the valve, then you can have equal or potentially even lower pressure in the actuator than in the accumulator. If the actuator has less area than the valve, then you must have more pressure in the actuator or it won't be able to open the valve. in the case of the Arizona cannon, an MPA-3 has much more cross-sectional area than the MJV-2 valve, so it works just fine with equal pressure in both sides. For firing, yes you need an MAV-3 valve or SMAV-3 valve and NOT an MAV-2 valve. I have tried the MAV-2 valve and it doesn't work. What happens is you press the button, sending pressure to the actuator to fire the valve. With a MAV-3, it then bleeds that gas when you release the trigger. With a MAV-2, it doesn't bleed the gas in the actuator upon release, so the gun just keeps blowing air until you're out of CO2. that really sucks, so don't try it yourself.
I don't actually know a part number. It's just a basic T fitting from my local hardware store with 1/4 compression on the top and side, and 1/8NPT on the bottom. I will see if they have a part number next time I go there. Another option is to make your own from 1/4" brass tubing, then chop off some 1/8NPT threads from another piece and solder those on. You can see some examples here: http://www.queensown.org/armament/armament.html you can find a fine example of a soldered tube breech about 2/3 down the page, and other possible methods are shown as well.
These would be cannon, designed to substitute for a torpedo with a 1/4 inch ball. Not locomotive torpedoes, which have another discussion devoted to them.
