Type7 - Robbe Rebuild.

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  • subkraft
    Junior Member
    • Jan 2009
    • 76

    #1

    Type7 - Robbe Rebuild.

    Hi y'all from Australia.....
    I've been lurking and loitering on here for a while now, learned a lot, so maybe now time to post something.

    Some years ago I did a Robbe U47, my first sub. Probably not the best choice, but, hey, had to have a U Boat. Replaced a lot of it, one of those beautiful etch brass decks, conning tower from Accurate Armour....a lot of resin to be ground out to make that work.

    Then converted it use a Engel piston tank. As a working model it was never much good. It was a cut up of the Robbe wtc piston tank filled from the rear, so sub always went down stern first....overpressure, huge turning circle, not much space for adequate batteries, direct drive...many shortcomings.




    So, new project....Build a new wtc for it.

    Through my work I use cad daily. This has extended to using a laser cutter to make parts. Signwriters often have them now to cut out acrylic lettering. Perfect.

    I've built all the parts as 3d models and designed a new wtc to address the problems. The set of parts have been done and redone a few times to get the fit right. Now I have what looks pretty much like a final set][/url]



    For those familiar with the Robbe model....the bulkheads sit on a standard plastruct section which sits over the beads on the bottom of the tube. All these pieces are held apart on threaded rods.

    Decided to post it as a build here....will keep me at it!

    CNC, lasering is a fantastic process. I could never make it all by hand. Worst thing about it is the acrylic cement. Fumes awful....never thought I'd wind up making model parts dressed like the guy in Breaking Bad....
  • Guest

    #2
    Re: Type7 - Robbe Rebuild.

    Looks very neat and tidy. I think the main issue with the Robbe was always the way the o-ring was compressed using the tray as a stressed element. This was okay as a dynamic diver, but once you introduce the internal pressure created by a retracting piston tank it puts a lot more strain on the mechanism, which to be fair to Robbe wasn't designed with that in mind.

    So what ballast system will you be using this time?

    Comment

    • ober freak
      Junior Member
      • Jan 2014
      • 114

      #3
      Re: Type7 - Robbe Rebuild.

      Very nice one!

      I also own a Robbe Type VII, it was the first sub of a friend of mine, we build it right oob, back in 2001.
      After a while we replaced the forward battery with a soldered dive tank operated by a Bruggen hose pump system with the pump direct in front of the tank.
      Dives really slow 90 sec or so, but was good enough for us school guys that days.
      I got it when he moved away.

      Comment

      • subkraft
        Junior Member
        • Jan 2009
        • 76

        #4
        Re: Type7 - Robbe Rebuild.

        Thanks....

        Aim of this is to get the piston tank working.

        Stressing the equipment tray to get a seal on the endcap sufficient to resist the overpressure of the piston is the problem.
        Its entirely dependent on the quality of the joint between the endcap and the tray.
        My idea here is to make a better joint here...and to pull the end cap down all round equally.

        Previously I used to close the piston, then bleed off the presure via bike valve on endcap.

        Got a bit together...

        Gearboxes from model aircraft, getting it to fit was a bit of a juggle....





        Comment

        • ober freak
          Junior Member
          • Jan 2014
          • 114

          #5
          Re: Type7 - Robbe Rebuild.

          Brüggen offers special bayonet lock rings for the robbe wtc http://www.modelluboot.de/Zubehoer/Bajonettver_e.html
          may this is an attempt to solve the pressure problem due to the operating piston.

          Comment

          • subkraft
            Junior Member
            • Jan 2009
            • 76

            #6
            Re: Type7 - Robbe Rebuild.

            I did buy one of those intending to use it.....it's still in the spares drawer....

            It would be an interesting job to retro fit it to the end of the main tube. You have to shorten it by 10, 15 mmm.
            Easy enough to do before you put the hull together....but after the hull assembled? Probably have to make somesort of tool to do it from the
            inside.

            The actual o ring on the fitting seems very fine in section.....I did wonder if it would really do the job. Once done, there's no going back, lol.

            Anybody done this successfully?

            Comment

            • Guest

              #7
              Re: Type7 - Robbe Rebuild.

              They work very well, seen a couple of them fitted, and of course the bayonets fitted onto Engel kits.

              Very difficult to fit on a completed model though as you say.

              Comment

              • subkraft
                Junior Member
                • Jan 2009
                • 76

                #8
                ....been a long time between drinks with this project. But have been chipping away. It has taken a lot of versions to get all the parts cut correctly. Finally getting there I think.
                Basic parts like this:

                Click image for larger version

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                • subkraft
                  Junior Member
                  • Jan 2009
                  • 76

                  #9
                  stern assembly. The laminated rings slot into the robbe endcap.
                  Click image for larger version

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                  • subkraft
                    Junior Member
                    • Jan 2009
                    • 76

                    #10
                    assembling from endcap forward. I've used a pair of electric aircraft gearboxes for approx 3:1 reduction instead of the direct drive in the original
                    Click image for larger version

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                    • subkraft
                      Junior Member
                      • Jan 2009
                      • 76

                      #11
                      Update the cad drawing with all changes.....at this point I'm making a few by hand.
                      Duplicate shapes are laminated together to build up parts.

                      Click image for larger version

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                      Comment

                      • tsenecal

                        #12
                        having an old retired robbe type VII myself, i find this a very interesting thread. hope to see more. thanks for continuing on this.

                        Comment

                        • ober freak
                          Junior Member
                          • Jan 2014
                          • 114

                          #13
                          Hi,
                          I have to rebuid my Type VII, too.
                          On the last run the technical framework and the pressure hull cracked.

                          So i have to redo the whole thing.

                          Marco

                          Comment

                          • subkraft
                            Junior Member
                            • Jan 2009
                            • 76

                            #14
                            Here's a couple of pix of this morning's quick assemble.....just have to try and adjust to get the overall length correct.

                            Click image for larger version

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                            Engel 750 ml piston tank up forward and inlet from bow so it will go down bow first. Inlet is still at the rear so a long run of tube but should be okay once primed. Engel's own twin tank systems use a similar long run okay.

                            There is a solid aluminium section that slots in underneath which makes it all quite rigid while clearing the locating bead in the bottom of the Robbe tube.
                            The screw joiner is beefed up and mounts into a brass plate that is bolted through two layers of 3mm acrylic. I'm hoping that having three rods running through to stern endcap will result in a more even seal around the o'ring. Apparently this needs to be a silicone o ring as opposed to the standard nitrile one.

                            Thanks for your interest....aim is to get everything assembled to prove all the laser cut parts then wire it all up.

                            From previous conversion I made the stern section detachable from the rear endcap so will look to make some improvements there as well.

                            Comment

                            • ober freak
                              Junior Member
                              • Jan 2014
                              • 114

                              #15
                              Your piston tank looks a little to far forward to me.
                              On my upgraded stock setup I replaced the forward lead battery with an soldered brass tank with the same length. That position was quite perfect.

                              Comment

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