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Ballast System for Small Submarine

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  • Ballast System for Small Submarine
    Make it simple, make strong, make it work!

  • #2
    redboat219- I think I got this one from you...I copied it and it works great. Thinking about scaling it up...he calls it a thruster but I'd say its a HVLP water pump...very simple .. that air tube is critical to limit ballast water level and no need for snorkel valve because built up air pressure seals off the snorkel check valve. BRILLIANT!
    Last edited by Bob Gato; 10-06-2020, 03:19 PM.


    • #3
      Hi Bob,
      can we see your version of the HVLP water pump.
      Make it simple, make strong, make it work!


      • #4
        Nope-I sold my house and I am waiting for a Covid delayed new construction condo to get its whole shop is in storage and has been in storage since July. But the thing I built was an exact copy of the one in the YouTube link...right down to the water bottles. I used a small coreless park flyer motor and a cut down park flyer prop...I did not want to change his design incase something was critical to the operation. It went down and came back up to PD and continued up once the snorkel check valve came above the surface -no problem coming up to and past waterline! When I get back in action, I want to build a un tethered self contained version I am confident that this simple design will lend itself to ANY size sub.-BG

        The pump looks just like the one in the video...basically a ducted prop...I'll be happy to share photos in a couple of weeks-(I Hope)
        Last edited by Bob Gato; 10-06-2020, 11:17 PM.


        • #5
          Thanks Bob.

          Click image for larger version  Name:	image_44817.jpg Views:	7 Size:	62.2 KB ID:	144255Click image for larger version  Name:	image_44818.jpg Views:	6 Size:	48.1 KB ID:	144256Click image for larger version  Name:	image_44819.jpg Views:	7 Size:	56.0 KB ID:	144257 In the link you showed during surfacing from depth the pump evacuates the tank but since the snorkel is underwater water continually enters and the tank remains full. As the pump's outflow is underneath the sub it functions as sort of "thruster" raising the sub up to PD where the snorkel can then take in air.

          The new system utilizes a sort of siphon instead of a flap valve to keep the sub surfaced. As long as water level does't go up pass the bend in the tube the ballast tank remains empty.
          Last edited by redboat219; 10-07-2020, 05:22 AM.
          Make it simple, make strong, make it work!


          • #6
            Stop me if I am wrong.. In Wat_Air's design, I understood that as the water is pumped into the chamber, the trapped air is under a slight pressure -both holding the check valve closed and reserving air with which to surface. In the video. The angled air tube sets the height that the ballast water reaches and any further running of the pump only pumps water in and right back out after it reaches that point. To surface, the residual air (under a slight pressure)allows the pump to start to vacate the tank until it reaches PD at which point the surfaced check valve allows air to enter and the boat comes up to waterline. The water bottle video is a little different than the diagram...In the diagram, almost all of the air is released and the thruster is heavily relied upon to surface (hence the need for a snorkel the same diameter as the thruster). The water bottle test boat uses the motor more as a pump and less as a thruster (note the small diameter snorkel-fish tank check valve). ...only one moving part!


            • #7
              Click image for larger version

Name:	img_6_m.jpeg
Views:	60
Size:	47.8 KB
ID:	144265 that red straw next to the pump/ thruster in the third photo also dictates how much residual air remains inside the ballast tank.

              Here is a diagram of the water bottle ballast tank. Yes its more pump than thruster.
              Attached Files
              Make it simple, make strong, make it work!


              • #8
                Not much remains above that straw (sure.. its not to scale) -in the "water bottle "version" the trapped air is whatever was above the air vent tube plus what's in the sail. That can be enough to start the boat on it's way to the surface?-It appeared that way in my swimming pool...As that air goes to negative pressure(very low pressures involved), a check valve could start to suck in water-I tried a snorkel float valve on top of the check valve and it looked promising- then I had to pack up to move.

                Sorry...I am working on memory here.


                • #9
                  Just found another one.

                  Same principle, a low pressure vented tank emptied by an axial flow pump but this one incorporates a small piston tank as a negative tank.

                  To dive, a vent is opened allowing air to escape through the snorkel and water enters the main ballast tank through the inactive axial pump at the bottom of the tank. The boat goes down with just the top of the sail sticking out. To dive completely, the piston tank is used.

                  To surface, the piston tank is emptied bringing the top of the sail up to where the tip of the snorkel can take in air when the axial pump is activated and the vent valve opened blowing the main ballast tank clear.

                  The use of axial flow pumps is common among Japanese RC submariner but not Westerners. Several years ago I remember seeing on a Japanese site a Japanese DSRV model that used an axial pump to fill and empty it's ballast tank. I can't remember if the tank was a closed type or vented.

                  I wondered if the axial pump used here can clear the tank even partially with the vent valve in the closed position.
                  Make it simple, make strong, make it work!