Recently on the Yahoo Big Guns Model Warship group, Rob Wood announced that WWCC is almost ready to release the files to allow users of (or those with access to) 3d printers to produce the most complex parts of two different cannon designs. One uses a positive pressure firing system like the Indiana cannons and most other designs. The other uses a negative pressure firing system based on a Quick Exhaust Valve. This thread is for discussion and creation of cannon designs based on these valves. The particular series of valves are these: http://www.fluidlinecomponents.com/files/Valves_Shuttle_Legris_QE.pdf Rob also posted some photos of a test cannon they have been using in combat. As you can see, the QEV takes the place of the MPA-7 pilot and the buna ball-valve that had to be custom made. This greatly simplifies cannon construction. Rob asked project lead Jeff Krolick to chime in, and Jeff posted some more detailed photos of the test design: And some photos of the valve: As you can see, the design uses a standard Indiana "upper" with the new valve and accumulator joined by a rotation bearing.
Jeff also posted some photos of another design that takes advantage of another "feature" of the QEV. With a little modification, the QEV can be mounted *inside* the accumulator, reducing the size of the cannon even further. Jeff said the only problem with the accumulator shown is that it is made from available materials and has a 12 cubic inch capacity, far larger than necessary. It is also designed to attach to the standard Indiana "upper" through a rotation bearing
Those of us in the Big Gun group began discussing the designs and asking questions, bringing our own knowledge and experience to bear on the problem of cannon design. For my part I knew that I would not be needing a rotation bearing, since my Agincourt's fire control system uses homemade barbette rotation bearings already, to avoid having to recalibrate after every cannon removal/reinstall. I realized I could move the QEV output directly under the breaches, greatly improving the efficiency of the gas usage, resulting in a smaller accumulator or lower pressure being needed, possibly both.
For a long time now, I have been trying to reduce the size of the cannon mounts in model warships to something the same size and volume in relation to ship size as those in the real ships. I even considered storing the ammo in the bottom of the turret stalk and using an electric "shell" hoist to raise the BBs to horizontal ball-bearing selector guns- which would work, but I couldn't squeeze in the traditional Indiana buna valve and separate parts. So I was very interested in the design using the QEV inside the accumulator, and suggested several possible substitutes for the 12" accumulator, including the reloadable motor casings used in the High Power model rocketry hobby. Shortly after posting those suggestions I realized how I could combine the various elements to produce a cannon design that would "drop-in" to my barbette rotation bearings and emulate a real-world turret stalk. The attached drawings show the original concept and it's initial evolution to eliminate possible long-term problems and reduce it's size. The original concept uses snap-rings and aluminum closures with 6061 aluminum tubing. I am also "reverse" engineering the design to make it simpler for individuals to make using pvc pipe or possibly exhaust pipe for the casing. QEVs have been ordered and I will try to make a couple of prototypes while glue and fiberglass are curing on Agincourt.
Please let us know when the design is ready for further testing! You guys are doing great work in every sense of the word(s).
Remember this is an open forum. Anyone can help or contribute and is welcome to do so. Kotori87 advised us that some types of QEVs may leak water in a sink. I didn't know this, or if this is the type that might leak, but now I'm including a drain port in the bottom disc of my designs, just in case. Some numbers: On WWCC's test cannon the barrels are sized for 1/4" rounds and the accumulator holds 6 cu. inches of volume. It delivered satisfactory performance at 150 psi. For the drop-in cannon, all the drawings are for an ID of 2" and use the 3/8" QEV. Jeff Krolick told us that the Legris QEVs are available on Amazon for $16.38. I got the last two until they restock. For more suppliers and information try this search: https://www.google.com/?gws_rd=ssl#q=7982 exhaust valve
rocketsmith, please do not publish my full name in a public internet forum. I prefer to maintain a single online identity, kotori87.
Hmm, that kind of looks like a dump valve. I'm intrigued. I also like the printed barrel clamp, I hate making those from aluminum. On the QEV - you have to maintain pressure in the accumulator or there is nothing to stop the water from entering. So if you are out of gas you can expect water in your gun.
My two 3/8" QEVs arrived, and they are a bit "chunkier" than they appear in the photos. The largest diameter is 1 1/4". In the drop-in cannon, that could be a problem with a PVC bottom disc- mounting the QEV off-center with a hexagonal hole and a gasket seal, *and* bolts to hold it together, and a drain plug. I had already thought about rounding the points of the hex to allow rounded edges in the plastic to avoid starting stress cracks but with a 2" dia. and that many holes it may be asking for it, even with fender washers. At some point a solid steel plate might be necessary to reinforce the plastic, rather defeating the purpose of an easy to build design. I was thinking of using four 1/4 x 20 long bolts or threaded rod and a 3/8" drain hole, now I'm thinking three bolts, reduce the size of the drain to minimum (remove a screw and force out water with gas pressure?) and if necessary move the QEV to the center to equalize stresses all around. Maybe lose the drain altogether and use a cordless socket driver for field stripping? There's still much thinking to do before cutting materials. Anyone know the OD of Iowa or Sodak or other triple barbettes for 1/4"? Of course with larger size comes greater force on the ends of the cylinder. I think the first order of business will be to construct a ridiculously over-strength unit from something like 1/4" wall seamless steel and find out just what the minimum required pressure is. All initial testing of the various designs will be done inside an old industrial gas cylinder (condemned) with the top half cut off- nearly 3/8" wall steel for safety.
I have always thought a feed ramp that is fed by a vertical hole/funnel would really help gas efficiency. This would allow rounds to drop from the magazine into the feed ramp (at a location "between rounds") but when fired the gas would just jam the rounds on the ramp against the end instead of flinging them out into the magazine. I probably need to draw a picture.
pardon my ignorance but those accumulators are huge how much gas does it take to fire a big gun one time i would think if you emptied a 12 inch accumulator every time you fired you couldnt carry enough gas for 5o rounds per turret. please enlighten me
My big-gun battleships both carry 20 oz CO2 bottle and easily manage over 120 salvos from all three triple 1/4 cannon before running out of gas.
While Big Gun ships may seem inefficient, remember that they are firing multiple rounds per barrel, at significantly higher mass per round. Fast Gun ships also run smaller bottles because they arm fewer cannons. I once did some measurements at a battle, and found that the Big Gun battleships I tested used around 1oz of CO2 to fire 50 rounds. That's actually quite comparable to good, hard-hitting Fast Gun cannons. Big Gun ships tend to carry large CO2 bottles because they tend to carry a lot more than 50 rounds per barrel.
