The magazine is actually one piece. I sawed the first one in half to help diagnose my problem, which is the half you see in the first picture.
Great idea, Mark, on both the gun and the magazine. That's a great application for 3D printng! And the assembled gun is beautiful. You, sir, are a master craftsman. Did you make the aluminum gun parts, or did you buy them?
I made all the aluminum parts myself. I spent a lot of time on the lathe last night. Well testing was a mixed bag today. On the good side, the gun fed reliably and the piston worked well. On the bad side, I could only get 140 fps and the tweak was constantly changing. So it turns out I have three leaks in the gun. First, and causing the most problems, is the O-ring sealing the loading hole. That one will require some redesign. I also have a leak on the threads holding the cap under the piston on. I suspect that one is because the threads are very sharp and are cutting the Teflon tape, so a little fine sand paper should take care of that. The last leak was on one of the joints, so I'll just have to re-glue that one.
I got the Parker O-ring handbook out today and machined an attachment to put an O-ring on the fill tube. Now it seals nicely - it's always better to do the right engineering first, instead of after a failure occurs. I cleaned up the threads on the bottom of the gun and now it seals there too. Finally, I machined a new attachment "L" for the top and changed to a BC style breech, instead of the Foster breech. Now at 130 psi I'm getting 195 to 205 fps out the gun, right where I want it. I still have a couple of issues to work out. First, I can see that the BBs striking the top piece right before they turn to go to the breech, is slowly driving the fitting off the up tube. So I don't really have enough area for the retaining compound to work. I may have to go to a brass "L" at the top for reliability. Second, if I open and close the valve quickly I get a normal single shot. But if I hold the valve open, it will go to rapid fire on me. So a little adjustment of CO2 lines is in order. Today, for the first time, I used the Genuine Innovations light weight 16 gram adapter and regulator from Strike. First thing to realize is that this is not a high flow regulator. When testing I fire off a round every 3-4 seconds, just waiting long enough to read the chronometer before I fire the next shot. I quickly noticed that the line from the regulator was frosting up after several shots. But more of a problem was that when I looked at the pressure gauge it read 160 psi, even though it was set for 130 psi. I put a 1 cubic inch accumulator before the valve and ran some more tests. Unfortunately, the accumulator didn't make a difference. So it looks like the setup will be good for 2-3 shots followed by a 30 second or so warm up time. Which may not be ideal, but it is workable for a tiny destroyer using hit and run tactics.
Have you considered running a section of the line under the hull. I have seen this setup on some of the old Freon based ships, and some big gun ships to help with frosting. The water acts as a heat sink to bring the temperature of the line up to the ambient temperature of the water more quickly with water being a better thermal conductor than air. It would add some weight, but should should help with the line issue. Maybe a section of 3/32" tubing with an elbow on each end...
I could run a line under the ship, it wouldn't be that hard. But the line was still flowing CO2, it just had a lot of frost on it. What I'm most concerned about is the regulator freezing, thereby making the pressure regulation unreliable. If I could put the whole cartridge adapter and regulator under the boat, I think it would solve my problem. That would also solve other problems like stability and lack of space inside the ship, but I think it might violate the rules.
I have the same composite regulator for my Orfey, and had anticipated such issues. My idea to control the problem if it arose (and obviously will) was to run a flexible tube from the underside of the bow to inside the ship, wire tie it to the co2 feed hose down its length, make a couple wraps around the base of the regulator, then exit it out the stern just ahead of the props..... not sure that it would work, there are a lot of iffy assumptions, but something I figure I could try. The theory was that the high pressure at the bow and low pressure ahead if the props might draw water through, which might help warm the bottle. My other thought was to run a servo controlled diverter valve to control the intake to the bilge pump to go in between pond water and bilge water, with the output wrapping around the bottle before exiting the boat, but its more complex, heavier, and adds more potential points for failure.....
I played around with the gun some more, replacing the straight up-tube with a piece of stainless steel tube, bent in a 90 degree arch. Gun tests went well, with up to 215 fps achieved with just 120 psi. So I'll probably run the gun at about 110 psi, which should help the life of the regulator. The gun mounts to the underside of the deck and is only held in place with the barrel right now. I'll add some silicone to the loading tube to seal it, which will make the mount stiffer. I figure I can just put shims under the rear turret to adjust elevation. Plus it makes me perfectly legal since the barrel exits the face of the turret. The penetration of the first level is sealed with a grommet so that I don't have to worry about water entering through the gun mount. And with the pretty stuff: There is no vertical room left in the ship. But I don't need any room left, so it fits perfect. In fact, the gun is back far enough that I can fit the pump between the motors and gun, where I wanted to put it.
The collar was to throttle the CO2 to the magazine if there was a problem with multiple shots. But the new up-tube seems to eliminated that problem. So for now, the collar is just sitting loosely on the line.
I've been working a little each night on the superstructure. Most of it is together now, I just need to add the life boats and life rafts.
Outstanding! Color me super-impressed! Will you bring it to any of the build sessions Mikey is hosting the coming weekends? More importantly, I assume it will be battling at Task Force 2 in a few weeks...
I hope to make it to one of the build sessions... the Admiral has ordered the spare bedroom painted, so it depends on how much progress I make on that. I do expect to run the Gridley at TF2, although that was never really the plan. The remaining hurdle is to mount the valve for the cannon, after that it's all standard construction.
I see it has been over a year since I put any time in on this project. So many projects, so little time. With the new 3D printer pretty much done, I started turning my thoughts to making ship parts. I started with the mount for the Gridley's motors. It functions as the protective armor, shroud to prevent water swirling, ESC shelf, and mount. I made the first one a little too tight but the second one was right on. Next I made a mount for the CO2 regulator and cartridge adapter. While I was at it, I made an insert to adapt the system from a 16g to a 12g cartridge. I made the first mount a little high, so I printed a slightly shorter one to keep everything below decks. A little pump screen on the back to keep out the balsa chunks. This is the 3rd or 4th iteration on the motor mount, hopefully this will be the last.
