Rotating Big Gun Cannons

Discussion in 'Weapons & Pneumatics' started by BigGunJeff, May 1, 2018.

  1. BigGunJeff

    BigGunJeff Well-Known Member

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    I've been working on some Big Gun cannons, and have come up with this design based on some older "Can Gun" style designs. I really like this concept because it's really space efficient and can house most of the things needed to function within a 4" wide x 3.5" tall space. Here's some more specifics:

    Firing mechanism: Quick Exaust Valve type using a 1/16 polyurethane disc as a flapper. A Clippard Minimatic MAVO-3P is used to fire the gun

    Gas supply: Fires strong at 80 PSI, and I've tested it to 100 PSI. Need to get more CO2 to go higher, but I think it will be fine. Accumulator Volume = 8.9 in^3 Gas is supplied through the base of the gun to the center of the bottom of the accumulator via an O-ring sealed port.

    Rotation: Uses a hobbyKing 4-turn sailwinch servo. Rotates ~300 degrees and is proportional to stick position. (Re-centers when you let go of the stick and it re-centers). Rotates on 3 acetal ball bearings

    Magazine: Shown is a large 6" magazine for large battleship and is bored to run 1/4" rounds. Holds hundreds of rounds... not sure how many, but probably more than you need! I could easily adapt this to smaller diameter magazines or smaller caliber. I made the magazine removable from the accumulator using just 2 screws that you can get to from the top. So if you sink, or otherwise want to service the magazine and barrels, it's easily removable.

    Construction: Accumulator is machined billet aluminum. All custom plastic parts (magazine, magazine cover, gun base, etc) are 3-D printed on Form2 printer.

    Let me know what you think. My cost of making one of these is pretty high at $170 ea. including rotation and elevation servos. I'm not set up to make these as a business, but I love this hobby and want to help others.

    Cheers

    Jeff
     

    Attached Files:

    Garrett, Nibbles1, jstod and 7 others like this.
  2. bmarkb

    bmarkb Active Member

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    Jeff,
    I’m impressed and really appreciate what you’re doing for our sect of the hobby - thank you!
    At the moment, I’m not in the market for more rotating cannon but may need to contact you in the future.
    Cheers,
     
  3. Kotori87

    Kotori87 Well-Known Member

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    Canister-style cannons are incredibly efficient, since they eliminate one of major direction changes in the gas path compared to Indiana-style cannons. That cannon looks incredible! I doubt you would even need to go above 100PSI.
     
  4. SteveT44

    SteveT44 Well-Known Member

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    Quite impressed. Very nice engineering.
     
  5. gunner250

    gunner250 Active Member

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    They look great and I'm very interested.... Though how much would it cost to make them
     
    Last edited: Sep 3, 2018
  6. rudyard

    rudyard New Member

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    Hi Jeff

    I'm very interested in buying your cannon. Building a Lutzow…if you are willing, pls let me know how you'd like to take my order.
     
  7. bmarkb

    bmarkb Active Member

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    Jeff,
    I’m looking for three as well, to complete my Texas.
     
  8. BigGunJeff

    BigGunJeff Well-Known Member

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    OK great

    I'll contact you directly to discuss further.

    Jeff
     
  9. nmmichris

    nmmichris Member

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    Jeff. Out of curiosity do you still make these? Looking to design/make or buy cannons for ships I have. I'm stalled until I get cannon situation figured out. Thanks
     
  10. indie2002uk

    indie2002uk Member

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  11. BigGunJeff

    BigGunJeff Well-Known Member

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    I'm still working out the bugs on this design.. In our last battle in November, I accidentally overpressured the guns to around 300psi. The good news is that the accumulators held together well. No issues. The bad news is that the heads of the fasteners that held the accumulators together were positioned in a 3-D printed part. They pulled through the part and the guns were ruined for the rest of the event. That was a good failure mode though... No damage to the machined parts and just need to print replacements for the damaged ones. Better than an accumulator blowing up!

    Anyway, to anyone interested, I have a simpler design that is closer to the Indiana style cannon... At least in terms of format. It is still a "Negative Pressure" or Quick Exhaust Valve type design and utilizes an off-the shelf component making it much easier to manufacture. I can easily make the valve base, magazine, and risers. The shipbuilder would make their own accumulator (presumably out of copper pipe and fittings) that screws into the valve base that has a 3/8 NPT port.

    I have a method of making the barrels described here:
    https://rcwarshipcombat.com/resources/3-d-printed-barrel-assembly.137/

    This just needs some integration and effort to make a complete design.
     
  12. nmmichris

    nmmichris Member

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    I'd be interested in seeing what you have thought of. Even if its design thoughts and I do the leg work of the fabrication. I have new toys (machines) on the way to help with my cannon issue. Your designs are awesome and appreciate your help/ input
     
  13. nmmichris

    nmmichris Member

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    What qev valve is it at least. I'd like to experiment with that some. Thanks
     
  14. BigGunJeff

    BigGunJeff Well-Known Member

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    Attached Files:

  15. nmmichris

    nmmichris Member

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    I had seen that and wasn't sure how that would work. I'm glad I wasn't to fat off base. I like the simplicity of it. Thanks a ton
     
  16. nmmichris

    nmmichris Member

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  17. nmmichris

    nmmichris Member

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    Another question jeff. Sorry trying to absorb as much info as possible to further my knowledge lol. Is there a function to the 3 holes that inline with the feed ramps to the cannon barrels? Curious if there is a design aspect that I'm missing.
     
  18. BigGunJeff

    BigGunJeff Well-Known Member

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    I like to print in PETG. I haven't had much luck with ABS.

    On the three holes... I've had issues with the ammo shooting back up the ramp and damaging the magazine cover. This magazine uses a plug to close off the ramp and let the ammo drop down the hole. When the gun fires the ammo can't shoot out of the ramp. In this way you get an (at least partially) closed breech, allowing more power into the projectile.

    I keep the ramp on the design and then plug it because it allows me to run a reamer down the feed ramps to ensure they're nice and clean. Capture.JPG



    Capture 2.JPG
     
  19. Kotori87

    Kotori87 Well-Known Member

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    Fascinating. It looks similar to Indiana-style cannons from the outside, but inside is very different. I am curious about some of the specific design choices you made.
    1) How well do the 3d-printed barrel bends hold up? I've seen steel brake line wear out after a couple years, so this is a serious concern for me.
    2) The ammo holes seem like they may reduce reliable feeding when low on ammo. Has this been an issue? Also, I assume you use 3d-printed plugs?
    3) Traditional Indiana cannons use a setscrew to adjust the height of the round in the breech, to ensure single-round firing. How do you set round height?

    My own printed cannons are coming along, just limited by available time and energy. Between work and winter refits, I'm running low on both :(
     
  20. Nibbles1

    Nibbles1 Well-Known Member

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    Awesome! Do you have files to build cannons for other sized bbs and 1 or 2 barrels?