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Launch mechanisms?

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  • Launch mechanisms?

    After getting my *** handed to me over the last few months of working out the straight running 1/48 scale G7E torpedoes I thought I’d start another self torture thread documenting the trials of trying to design what I think might be the most ideal launch tube design for type VII subs in 1/48 scale. What do you think?

  • #2
    Compressed air, spring or water pump.
    Direct impingement or floating piston.
    Make it simple, make strong, make it work!

    Comment


    • #3
      Originally posted by redboat219 View Post
      Compressed air, spring or water pump.

      Direct impingement or floating piston.



      Good question




      I should probably start out by clarifying what I was attempting to say last night while half awake just before heading off to bed.




      Now that the 1/48 scale G7E type torpedoes are mostly finished with development, I thought it might be better to start a new thread on the launch mechanisms instead of lumping the build in with the Torpedo thread.




      The submarine kit that I’m now attempting to develop launch mechanisms for is specifically for the Arkmodels 1/48 scale Type VIIC. The build will attempt to utilize the kit’s already molded in place features that were intended originally for the manufacturers torpedo launch system that to my knowledge was never available? The goal of the design is to come up with something that fits into the kit requiring minimal to no modifications to the kit.




      I really like the work that David did with his gas torpedoes and launchers. I also really like Manfred’s electric torpedoes and launch mechanisms. Especially the launcher he developed where the doors on his sub open and the torpedo swims out of the tube all with the single pull of that tube’s mechanism. Brilliant.




      The best designs in my opinion no matter what it is, follow the KISS principle. This build unfortunately will not be keeping to that principal, at least at this early stage.




      The launch tubes will use a floating piston to push the torpedo out of the tube. I’ve noticed pushing the torpedoes out this way (electric torpedoes) opposed to pushing them out with air or pumped water reduces water being forced into the torpedo’s propeller shaft tube. I’ve also noticed much less prop cavitation upon launch pushing them out this way opposed to pushing them out with a blast of air.




      Pushing the torpedoes out mechanically with spring loaded mechanisms also seems very effective and very easy to reload quickly. To my limited knowledge, the Type VII subs (as well as other German Navy subs) could either launch torpedoes with a either a blast of air or install a piston in the tube behind the torpedo and push it out the tube that way as to not give away their position with blast of air bubbles. Wanting to follow what the original boat’s had as an option for launching a torpedo, I chose to use the piston method.




      Liking the mechanical spring method, I thought I’d attempt to marry the two together and create a sort of air spring by using a separate air reservoir that holds the right amount of air volume and pressure to push the piston down the tube without dislodging the piston from the tube. So far in early tests this seems to work well although adds complexity to the design.




      To activate the torpedo door and launch of each tube, I’m currently exploring designs that use a small pneumatic cylinder although a small linear electric solenoid would also probably do the trick. Not sure how they each compare in available force, and travel for a comparable size?

      Comment


      • #4
        Have you tried just letting the fish swim out on it's own?
        Make it simple, make strong, make it work!

        Comment


        • #5
          Actually haven’t tried since the fish were switched to a counter rotating propeller design. I will have to give it a try once the torpedo is repaired!

          Comment


          • #6
            Another way to eject the fish might be to pump water behind it or the piston. No air tank to fill.
            I really like what you've done. Looking forward to see your work and ideas.

            Comment


            • #7
              Nick,

              As you allready know i operate both the spring assisted as the free outrunning tubes, when you go this way, make sure you have enough slits in the tube to get the water all around your torp especially near the propellors of your torp, pump up your runningtime to 7 sec, this will counteract the time to depart your tube.
              Spring actuated is suited for large boats since it's more complex with the triggersystem, the free running type is much more KISS, less moving parts, only the magnet and tube door attached to the trigger rod, disadvantage, you need one servo by tube.
              Also keep in mind the balance of your boat after firing each torp, our electric runners have bouency, each shot will alter the balance, my type VII has a cart with lead inside which counteracts the balance by moving the opposit direction restoring the balance of the boat.


              Manfred.
              Fertig zum unterwasser.

              Comment


              • #8
                I'm sure that this thread is going to be good!
                Here's an Idea- how about doors that open with the same water that launches the torpedo and spring-loaded to close. A pressure shuttle valve that allows water to partially shunt over to the torpedo tube to launch after a set pressure has built up (maybe thru a snubber orifice) , assuring that the door is open first. When the water is stopped after the torpedo has left the tube, the pressure holding the door relieves and slowly, thru the orifice -and the door slowly springs closed. Regarding the launch piston, why not retain it with a nub or a pin that sticks into the torpedo tube a few thousandths -possibly three to keep things stopping square-BG

                Comment


                • #9
                  Hey guys,

                  Great advice and design ideas! Thank you!




                  Scott,


                  I like the idea of pushing the fish out with pumped water. I’ve noticed in earlier tests exploring this method, that water would be pushed into the prop tube even with a close fitting tolerances and a bit of jelly lube. Pushing the piston with water would work well.



                  Manfred,


                  Thank you the helpful tips about the slots in the launch tubes to let the fish swim out of the tubes. I would like to get timers that I could increase the runtime setting. I’m limited to setting the runtime to 3 or 5 seconds only with the current timers. Having a adjustable timer has been on the wish list. I like the sliding lead weight mechanism you described for your VII. Great idea! I have been concerned about the same potential ballast adjustment issues after launching the torpedoes. What I cannot answer yet is how the floating piston type launch will effect the ballast. After the launch the piston will remain at the end of the tube near the muzzle. The rest of the tube after the launch will be dry with a very slight positive pressure. Was guessing I may need to add a small piston type trim tank to fill with water after each fish was launched. Again just a wild guess for now until I can see how it actually behaves.




                  Bob,


                  I’m following exactly what you’ve described. That would work. I did test the piston launch tubes with the floating pistons very early on for the plain reason that air is compressible while water is not. I was thinking that controlling a measured amount of water to move the piston down the tube would be a lot easier. The only thing I noticed immediately was using the same size syringe as what was used during the pneumatic tests required a lot more force when using water. Not a big surprise since the diameter relationship effectively between the two cylinders was not optimized for less force required. It would be interesting to explore the use of water or hydraulics further. I considered using a positive stop for the piston at the end of the tube like the real boats used but realized my tubes dimensions were not optimized for this. The torpedoes are .4375” in diameter. I’m using .500” OD tubes with a .014” wall. The tail fins on the fish are designed like the full-size counter parts in that there are short guides at the ends of the fins that stick out further then the diameter of the torpedo body. What I’m left with is .012” clearance around the torpedo. The floating piston locks onto the fins of the torpedo making the leading edge of the piston roughly the same .012”. I was worried that adding a stop would damage that edge after hitting it a few times and the stop would also need to have an ID large enough for the torpedo to past through without resistance. The floating piston is made from Delrin and does not use o-rings to seal to the tube. I found o-rings creates too much drag. It’s instead a precision machined fit that seals great but still slides very smoothly in the bore. With a small amount of tweaking the design could be optimized to use a stop. It just wasn’t on my radar originally when I started.








                  ​​​​​​​






                  I was able to make some more progress yesterday and this morning on the prototype launcher. I have one tube functional now. This is not meant to be a final design at all. I’m still in the process of testing each individual component and system for the launcher that I originally envisioned months ago. The difference is I’ve now been able to put them all together to see how and if they work as a system.

                  So far I’ve tested the muzzle door and outer shutter opening mechanism. The floating piston for launching. The reserve air storage tank and poppet valve to send the piston down the tube the correct distance. The last two tests was seeing if the pneumatic piston at under 15psi would have enough force to open the doors and trigger the poppet valve. The final test in the set was to test the Rube Goldberg mechanism I came up with to allow it all to happen.

                  Here’s some photos from today of the launcher in it’s current state. I used a common air source rigged up from a temporary brass and copper manifold to provide air to both the pneumatic cylinder and the poppet valve to initially test the function of the assembly. In the video links below, the floating piston in the tube was removed so it would not shoot out and fly across the room anymore more times than it already had this morning. Later I separated the two systems and added the poppet valve reservoir tank and reinstalled the floating piston.


                  https://youtu.be/zRsGPZW8eD0


                  ​​​​​​​https://www.youtube.com/watch?v=U0BTc3Hjwwk



                  ​​​​​​​Nick

                  Comment


                  • #10
                    Nick,

                    I've enjoyed your Rube Goldberg contraption running your tubes on air, a good engineer feat, you mentioned that you have a timer issue with increasing the time, i would go the spring assisted tube, less bulky as the air/gas system, dugged up some vids from some time ago,

                    https://youtu.be/QAKQZEoY_X0

                    It's about my reartube, the principle is the same as with the front tubes.

                    https://youtu.be/SvPFp-iaEHQ

                    Practical use with a dummy and a real torpedo, the spring gives the torpedo a nice headstart by being pushed out of the tube.

                    https://youtu.be/Nk98gAA5klY

                    And some actual footage when testing inside the bathtub.


                    Manfred.

                    Fertig zum unterwasser.

                    Comment


                    • #11
                      Originally posted by MFR1964 View Post


                      It's about my reartube, the principle is the same as with the front tubes.



                      Manfred.
                      Click image for larger version

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                      Last edited by redboat219; 10-11-2020, 01:43 PM.
                      Make it simple, make strong, make it work!

                      Comment


                      • #12
                        LOL, Finish your damned Kilo

                        Manfred.
                        Fertig zum unterwasser.

                        Comment


                        • #13
                          Originally posted by MFR1964 View Post
                          LOL, Finish your damned Kilo

                          Manfred.
                          Ditto.

                          One project at a time.

                          So what each project takes over a decade!

                          Who's counting? Wait ... I am!

                          David
                          "... well, that takes care of Jorgenson's theory!"

                          Comment


                          • #14
                            Manfred,

                            Thank you for taking the time to dig up and post your videos.

                            Redboat, you beat me to the punch on the “rear tube”. LOL!!

                            Watching the videos was very helpful. I recall watching some of those videos you just posted last year. I remember thinking to myself back then, damn this guy has serious talent. Seeing them again was refreshing and perfect timing. Your spring actuated launch designs are very neat and well executed. Definitely a lot less bulky than the gas launcher I’m screwing around with currently. It is faster to reload too. Very nice work!

                            The transmitter I am using has 6 channels, but has only a single channel available for launching all five torpedoes individually. Wish I would’ve stocked up on some of the 16-18 channel radios years ago. Don’t like the 2.4ghz stuff for anything other than surface or air.

                            Last winter is when I came up with the concept for the launch mechanism that I’m just currently getting around to working on now. The idea was, the concept would potentially address the single channel needing to make each tube and door sequence work that I was hoping for. Back then, I was also hell bent on using gas to eject the torpedoes. That was before the floating piston was introduced into the mix which cancels out the visual effect of a gas launch.

                            I really like both the spring launch as well as the swim out of the tube designs. I can see with a small bit of design work both of these launch methods being made to work successfully with a single channel as well. Could use electric linear solenoids instead of electric gas solenoids. This is definitely a strong argument to move the design work towards this architecture layout.

                            Damn it! I’m so invested into to contraption I’m knee deep in currently. I should probably finish it out for the sake of it before switching everything up! Thank you for the reset!


                            Nick

                            p.s. There’s a Kilo sitting off your stern. Fire when ready!
                            Last edited by Monahan Steam Models; 10-11-2020, 10:11 PM.

                            Comment


                            • #15
                              David M addressed the single channel multiple launch using a ratchet mechanism activating a sort of music box drum with protrusions that trips each individual launch tubes. Change the pattern of the protrusions and you can either fire all tubes at once or in what sequence you program, tubes 1,2,3,4, or 1,3,2,4,.... I know I've seen it recently in one of David's post. Maybe he can repost it here and tell you more about it.
                              Last edited by redboat219; 10-11-2020, 10:35 PM.
                              Make it simple, make strong, make it work!

                              Comment

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