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1/48 G7 Torpedos

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  • #61
    Nick-you have "nailed" it. It goes as far and straight as you'd really want it to! I guess increasing the prop speed by a factor of 5 gave the thrust that you need- now for the really hard part-making them cheap and fast enough that if you lost them-no big deal!

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    • #62
      Thanks BG! I was definitely happy to see the speed return to the torp again. There are still more revisions to come before I’d say the design is mature. Looking forward to playing around with the capacitors when they arrive. May not need to boost the voltage but that will depend on what the final motor choice is. Like you said earlier, weight is a huge factor and one of the main things that has driven the design choices. Performance is the next driving design factor and then ease of production like you mentioned. It’s been a fun experiment so far.

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      • #63
        The various super capacitors I ordered earlier this week arrived this evening. I was anxious to see what they could do so I did some rough bench testing to start out with. All the various caps ordered are in the 8mm OD can type style. The variances are can/body length, voltage (in this case 2.7 or 3v) and Farad rating. The biggest being a 3volt, 3 Farad 8mm D x 20mm L. There were longer body super caps in this diameter available in a much higher Farad rating (6 Farad being the highest I found) but the current design constraints of the available room and ballast of the torpedo dictated the cap dimensions I chose to order and test.

        Here’s what I found. I’m going to focus on the biggest super cap mentioned above. After a quick full charge on the bench top variable power supply, the 3v 3F super cap was able to run a spare motor I had on hand, (matching the currently installed in the torpedo) high performance 6mm x 15mm coreless motor for and impressive amount of time in air with no drag. Rpm’s dropped very slowly over what felt like a long time in a subtle manner. That’s not a very scientific measurement I know but I grew bored of hearing it run as it was much longer than the 5 second timer installed in the torp and I disconnected it from the super cap. Impressive to say the least.

        Where the rubber meets the road. I jumped over to testing this super cap with the torpedo on the bench in air no drag as it is configured currently with the timer module, 6x15 hipo motor and counter rotating prop gearbox minus the 3.7v 60mah LiPo. At full super cap charge, the motor started out strong but faded away in power and stopped before the 5 second timer shut the power to the motor off. Ran the test a few times and same results. Need to check if the timer has a low voltage cut off before I can make any assumptions.

        I followed the super cap testing up with plugging the LiPo battery back in and the torp ran strong the whole 5 seconds and for repeated back to back runs in the same charge.

        ive attached a few photos of the super cap and LiPo for dimensions and weight comparisons.

        The super cap is definitely a serious design consideration compared to a LiPo depending on the design. I feel if the torp design I was working on currently ran one motor, direct drive, no extra gearing or timer module, keeping everything light and clean, it is unbeatable.


        Attached Files

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        • #64
          Thank you sir!

          This has been a fun design study and I hope that some of the information adds to the library of knowledge already out there.

          If time permits today, I would like to run a couple more tests with the super caps. As BG has pointed out, the need for the timer module can be removed, especially if the charge capacity is well matched to the desired run time. I suspect the short running time I witnessed yesterday evening may have something to do with the timer module and not the super cap. Plan to omit the timer and LiPo in the next test and use just the super cap directly with the motor and gear box.

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          • #65
            Quick Update:

            Just ran a couple more tests this morning with the largest 3 volt 3 Farad capacitor. This time the capacitor was connected directly to the motor along with the counter rotating gearbox, with the tail cone and props installed. The results were as follows:

            21 seconds of total runtime in air no drag until motor completely stopped. Rate of rpm noticeably began to drop after about 4.5 seconds

            8.5 seconds of total runtime with props submerged in tank of water until motor completely stopped. Rate of rpm noticeably began to drop after about 2.5 seconds

            67 seconds to completely charge capacitor until current flow dropped from 500mah to zero using 3 volts

            Much different results from yesterday evening’s tests that still utilized the timer module. I believe the module begins to cut out the closer the input voltage reaches 2 volts

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            • #66
              If i'm correct, Dan Achur has made succesfull capacitors torpedo's, no timer needed, i run my own torps on a 1S Lipo, no timercircuit and single prop, use the counterrotation for stabilising to get a straight run, they tend to swing off when the lipo runs low.
              On one charge i get about 15 runs, i did think of the capacitor way, but the configuration of my launchtubes makes it too much complicated.

              Manfred.
              Fertig zum unterwasser.

              Comment


              • #67
                Manfred, thanks for sharing your experience with torpedoes. I really enjoy seeing your build posts and the progress you’re making on your projects. You’re a great builder!

                The design for these torpedoes sounds very similar to yours. For me, this was also mainly due to how the launch tubes will be configured in the type VIIC. I do like the way 1s LiPo performs and during the test runs of each design, being able to get multiple runs from one charge has been helpful.

                With the lack of multi channel expandable surface radios available today, I’ve had to compromise on how to go about launching each of the 5 tubes individually using only one available channel. I plan to use one of Kevin McLeod’s launch module for gas solenoids and launch each tube with propellant. I think I’ve come up with a way to get each forward torpedo door to open just before the launch occurs for each tube and then close after. Getting the torpedoes perfected to me seems like the logical first step. Then I can move on to the launcher.

                Nick

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                • #68
                  Nick...no need for expensive expandable radios to launch torpedoes. Five would be tough... but four would be easy using an inexpensive 433 MHz garage door/ light rc unit...tiny key fob like transmitter is simply clipped, Velcroed or two side taped to the main transmitter. Four push buttons each control a 10 amp relay.
                  Attached Files
                  Last edited by Bob Gato; 07-30-2020, 07:57 PM.

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                  • #69
                    Okay that’s cool! Thanks for sharing this! Btw, I ordered a couple more super caps today. There’s a few 3v 5F’s on their way and a few 3.8v 25F‘s!!! Mwahahahaha!

                    Couldn’t help myself when I saw it! The hot rod builder in me had to do it. That one they called me shortly after I placed the order to say it’s considered restricted and can’t be shipped by air. Has to go ground.

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                    • #70
                      Paleese! Are they kidding! They are just aluminum foil and wax... somebody must have thought they were batteries...
                      Wow -i​​​​​​i can't wait to see those heavy hitters perform.
                      Last edited by Bob Gato; 07-30-2020, 09:09 PM.

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                      • #71
                        It was weird, they shipped the 5F caps by air today but would not ship the 25F caps by air. Oh well, the design is starting to split paths. I have parts coming to optimize the LiPo version as well as the super cap version. Some latching and non latching double throw reed switches are on their way too. Mainly for the super cap design.

                        In all of this, I still need to focus now on designing optimized scale counter rotating prop designs. To date I’ve been using modified props off a hoard of 1/125 type VII revell u-boat kits left over from 20 plus years ago when I converted one of those to RC.

                        To make design matters even more challenging to navigate, I’ve been playing around with the idea of running twin 4mm counter rotating motors each driving their own shaft and using a small custom designed pc and some code to sense torp body roll and compensate with adjusted individual motor Rpm’s control to correct body roll. Wouldn’t take too much to do. I would think you could almost steer the thing by manipulating the prop thrust

                        Comment


                        • #72
                          Originally posted by Monahan Steam Models View Post
                          To make design matters even more challenging to navigate, I’ve been playing around with the idea of running twin 4mm counter rotating motors each driving their own shaft and using a small custom designed pc and some code to sense torp body roll and compensate with adjusted individual motor Rpm’s control to correct body roll. Wouldn’t take too much to do. I would think you could almost steer the thing by manipulating the prop thrust
                          That is insane, anxiously waiting for this!

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                          • #73
                            Not too insane when you boil it down to the basics. Let’s look at it mechanically for a sec. Can you fit two 4mm motors side by side in a 10mm space. Yes you can. Can you provide the proper distance from each motor shaft centerline to prop shaft centerline in a 10mm circle foot print. Yes I think so with the right gearing. It’s much easier to have control with two variables in real time then only one where you have to get the mechanical dynamics balanced out just right. Im taping this out on a smart phone which has micro accelerometers sensing the exact position of the phone. Think about that for a moment, fairly small light weight components right? Micro RC airplanes, helicopters and drones with gyro stabilization hardware use similar micro sized chips. I think it’s achievable with some r&d work.
                            Last edited by Monahan Steam Models; 08-01-2020, 10:39 AM.

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                            • #74
                              Currently waiting for new bits and pieces to arrive for the next rounds of torpedo designs and testing. In the meanwhile here’s a video of a marine steam engine I built from scratch a few months ago being test run on compressed air before being sent out to it new home. Every single part on it is machined and made from scratch. I used to manufacture these in my shop along with the boilers and other bit more than a couple decades ago and hundreds of these are around the world today. I stopped making them back in 2010 to focus on design and machine work for the labs and the private sector but they’re still fun to play around with every once and a while.

                              https://youtu.be/2wnT55L4wkg

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                              • #75
                                Starting the process of adding some of the finer details to the G7E Torpedo parts. Here’s the current tail section CAD model with the beginning details being added now that the mechanical functioning part of the project is almost complete. Rudders, planes, hatches and other details will be added soon

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