Piston ballast tank vs Floating piston ballast tank

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  • Monahan Steam Models
    Captain
    • Apr 2020
    • 755

    Piston ballast tank vs Floating piston ballast tank

    Hey Everybody,

    Does anyone have some first hand experience they would like to share using floating piston ballast tanks? I find them interesting because the ballast tank appears to fill and drain similar to the more common screw driven piston tanks but with out the extra space required for the traveling screw. If the performance is close to that of standard piston tanks, it seems like it could be a neat and more compact way to go. Well I guess that is besides the room that would be required for a water pump or two.

    Thanks!

    Nick
  • Monahan Steam Models
    Captain
    • Apr 2020
    • 755

    #2
    An example in this video of what I am referring to as the floating piston ballast tank type. This one is neat because it is a twin cylinder on one pump set up. The more common ones I’ve seen are single pump single cylinder.

    My experience has mainly been with vent and sink, blow and go pressurized gas ballast systems besides some miniature dynamic divers I built as a kid.

    Looking at adding smaller piston type set ups mainly for additional fine trim control and depth control.

    Video: https://m.youtube.com/watch?v=cBMO-EMTEJ0

    Comment

    • redboat219
      Admiral
      • Dec 2008
      • 2735

      #3
      Aren't floating piston ballast tanks just essentially water pump/ bag ballast system but you swap out the bag for a syringe. Looks neater than a floppy bag but still has issues with internal pressure build up.
      Make it simple, make strong, make it work!

      Comment

      • Monahan Steam Models
        Captain
        • Apr 2020
        • 755

        #4
        Yeah, that was what I was curious about. Seems like the same pressure problems of a regular piston cylinder only more compact in the way I was thinking of using it and happier to see ya then a floppy water bag. I would think it would still give the same fine ballast adjustments if kept small and used in conjunction with a larger main tank as a secondary trim control
        Last edited by Monahan Steam Models; 08-02-2020, 11:57 PM.

        Comment

        • trout
          Admiral
          • Jul 2011
          • 3545

          #5
          I am working on a piston system for the Gato and may try the floating piston. I have an WTC from small world models and it uses a floating piston.
          If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

          Comment

          • Monahan Steam Models
            Captain
            • Apr 2020
            • 755

            #6
            Trout,

            Thanks for posting. Is your SWM’s wtc functional? Have you had a chance to test it?

            Comment

            • trout
              Admiral
              • Jul 2011
              • 3545

              #7
              Yes, I played with it. The design as a whole is OK, but it is designed like the New SubDriver in that it uses modular sections. These leak a lot on this WTC I have (meaning the SWM WTC) and I did not trust it for use. That being said, the piston moved fine and pressure build up was not an issue. My 3.5" piston on the other hand is 19" in length and has a 2.5" piston with 7" travel. It does build up pressure, but that is still manageable. The pushrods use a simple o-ring in a compressing type mount. That holds back air from leaking just fine. Future ones I build will not be that compact, it was more me seeing if I could.
              If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

              Comment

              • Monahan Steam Models
                Captain
                • Apr 2020
                • 755

                #8
                That’s great feedback and exactly the info I’m looking for. Thank you!

                Comment

                • Subculture
                  Admiral
                  • Feb 2009
                  • 2119

                  #9
                  Wasn't aware that SWM did a pump based piston type module- they tended to use fixed tanks with propel/gas.

                  RPMtech and RCsub workshop did pump based piston modules.

                  Comment

                  • trout
                    Admiral
                    • Jul 2011
                    • 3545

                    #10
                    Andy,
                    you are correct, I mixed up names, it was Rick Palumbo’s system (RPMTech). Thank you for catching that!
                    peace,
                    tom
                    If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                    Comment

                    • RCSubGuy
                      Welcome to my underwater realm!
                      • Aug 2009
                      • 1768

                      #11
                      I used that style of actuation for my periscopes in my current Type XXI build. I'd hazard a guess that a pump-based system like this would draw more current than a screw-type piston system, but that's just a guess. Making your own large-diameter ballast tank with this methodology shouldn't prove to be too difficult. If the pressure buildup is too large, I wonder if it would force the syringe back in and flow water back past the pump if you didn't use a valve to close the line. Not a problem if you went with a peristaltic pump, but if you used the higher flow gear pump, it could be an issue.

                      Comment

                      • Monahan Steam Models
                        Captain
                        • Apr 2020
                        • 755

                        #12
                        Bob, I’m hearing what you’re saying. I was thinking on a smaller scale about trimming for torpedo loss after launching mainly in the forward section

                        Comment

                        • trout
                          Admiral
                          • Jul 2011
                          • 3545

                          #13
                          Originally posted by Monahan Steam Models
                          Bob, I’m hearing what you’re saying. I was thinking on a smaller scale about trimming for torpedo loss after launching mainly in the forward section
                          Perfect use for a small piston, for that matter, it is a fixed weight, so a piston using a plane retract setup would work, like I did on my 1/96 scale Aluminaut. Love your thinking there Nick!

                          This gets my mind thinking in that when you launch it simultaneously moves piston or the piston motion triggers the launch.....oh the possibilities.
                          If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                          Comment

                          • Monahan Steam Models
                            Captain
                            • Apr 2020
                            • 755

                            #14
                            Trout I like your thinking!

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