Big Gun cannons with MJV valves have been in use essentially from the beginning of the hobby. Their construction is quite simple. Here is an installed example as a destroyer torpedo cannon: Air is stored in the MAT accumulator tank on the right, in this case at around 120PSI. To fire, an MPA-3 actuator (brass cylinder on the left) opens the MJV-2 valve (brass block in center), which causes a pressure wave down the barrel that launches the bb. This particular example is set up as a single-barrel multi-ball torpedo cannon, firing three 1/4" ball bearings from a single barrel and is reloaded on shore using a 12v air compressor or bicycle pump. Reloading MJV valve cannons only require a few extra parts: The T fitting you see has 1/8NPT threads on the bottom, and 1/4 compression fittings on the side and top. To the left is a 1/4 compression support insert, that is used as a selector piston. The barrel shown is not the correct size, but it's all I had readily available. When firing, the gas rushing up from the MJV-2 valve lifts the selector piston, closing the breech. The example shown is suitable for .177" and 3/16" rounds, and T fittings for 7/32" or 1/4" rounds can be ordered online or manufactured at home with hand tools like a hacksaw and file. Remember that most Big Gun cannons require a lathe and mill to produce, so this significantly simplifies cannon production. What atomicpunk235 is proposing is to modify the headspace on this type of cannon to allow two, three, or four rounds into the breech to emulate the firepower of a multi-barrel cannon. This is significant. single-barrel multi-ball cannons are simpler and smaller than their multi-barrel equivalents. Not only does this idea allow easier construction of battleships, it makes gun-armed cruisers a viable option.
Like these guns. We are trying to some new rules in an attempt to simplify the game. These shoot a single BB every 2 seconds at 100 PSI with a .75 tank and with only the barrel rotating you can use the old style gun with very little air and these take an hour to make, when I tested them they shot through 2" pink foam a cheap plastic container and bounced around the garage. Big Gun Jeff and Sammy want to use the Vacu Destroyers with fast guns so we are trying a 2 second rate of fire for BB's and removing the limit of reloads for torpedo guns so we can get simple guns to work and not rely single shot.
Do you have a pic of what's under the pulleys? I'm curious what keeps the rotating barrel assembly from being pushed out of the top of the gun?
See the spacer ring on top, that fits under the deck and that keeps it in place and the loader at the bottom of the pic is all that is there. You can use a dish or tube mag and this boat has both. It is Mogami and these guns will fit in a DD with a smaller rotation ring for the belt. Mogami has 3 rotating singles and 6 1/4" reloading torpedo guns. It will be a very powerful cruiser. These are all old school guns and I keep using 1989 tech because it works, I think better than all the new stuff (KISS). I tried to lower costs and expand the club in the mid nineties by cutting the number of guns because after 7 years we still had 10 active members and that's because of cost, complexity and availability of Big Guns. In 1992/93 the club had switched to playing 1/72 over 1/144 because it uses the guns above in most boats. I did not want the 1/144 format to die so Deryk and I convinced 80% of the members to cut the number guns and torps to save the scale. It would have been nice to go further but I took what I could get and it worked better than we could have hoped. I have a similar idea to yours but it would be this gun one round per shot, limited rounds, no rate of fire and use CO2 only plus you have to have an accumulator tank on each gun and that will create a rate fire (no more counting). Imagine arming an Iowa for $150 ish for the guns and doing the same amount of damage using a lot less CO2. The guns above are out of my gutted 1/72 destroyers and both of our ideas will not pass because the same people are in charge and I am done FIGHTING off the water. Maybe another group can try this and I am telling you it works.
OK. A couple more questions. What triggers the "actuator"? A KIP style solenoid valve? How would one modify the piston selector mechanism to allow more rounds into the assembly? It seems like the both the "throw" and the length of the selector probably have to be longer?
See the actuators next to the on/off switch for the gas, a servo pushes the plunger but you can use the same tech as fast gun. I use a set screw to determine the # of rounds per shot, see loader in first pic's and I don't use a piston. The problem with both ideas is that it is not sexy. If someone ask's you how many gun's are in the boat and you say 3 it does not get the same response as 18. What that person does not know is that only 6 out of 18 can put a hole in 1/8 balsa but it just sounds far more impressive. I know not all boats are quite that bad but most are. After my first return battle I could not be leave how may dents I had on 3/32 hull, but as I said it is all moot and I am just venting my frustration because it does not harm me with the exception of lower turn out because I make my own guns and I built my last set of multi barreled guns for my pocket. I will help the club with reloading torpedo guns for cruisers because I think that would be the easiest way to get someone on the water with 6 1/4" guns that can fight the whole battle and not running to reload.
