magnets get weak?

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  • a1965l
    Lieutenant Commander
    • Apr 2020
    • 147

    magnets get weak?

    Took the Akula to the neighbor's pond today for some water time. Pre checks good, in the water, worked out the bubbles and got underway. I very quickly lost control of the rudder. Recovering the boat, I find that the rudder is loose, as the magnetic connector has come uncoupled. That happened when I first started running it.. but it was because the pushrod was contacting the driveshaft. I reduced travel and the issue dissapeared. Until today. With the top off, I verified that the linkage was still clear of teh driveshaft, and that there were no other interference issues. I also verified that the WTC was sitting squarely in its foundations and was on the index pin. In the water with the top off, and I find that if I cycle the rudder quickly, it comes disconnected on the pull stroke. Dosen't happen in the air. I've never had an issue with cycling the rudder quickly in the water before, so... what the hell?
    "It does not take so many words to speak the truth" Chief Joseph
  • Bob Gato
    Captain
    • Feb 2019
    • 826

    #2
    Magnets attract more strongly exponentially as they get closer...is it possible that there is a coat of rust on the magnet's face? or paint? or filings?

    Comment

    • Bob Gato
      Captain
      • Feb 2019
      • 826

      #3
      Is it possible that you accendently have the rudder trim set to a setting that you normally dont have set? Did you change anything-like the servo (might be faster and more powerful?) Change the ubec? (more servo voltage) change to a lipo battery? Does the rudder swing without binding when disconnected? Did you accidentally go from low rate to high on the rudder control? I got a million of them-I'm here all week!

      Comment

      • a1965l
        Lieutenant Commander
        • Apr 2020
        • 147

        #4
        The only screw-up I pulled was running it on the 688's settings briefly. The only real difference in the two, at least at that time, was that I had set all the travels back to 100% for the new boat. The magnets look all nice and shiny and I dont' see any fod on them. Haven't changed anything electrical in the boat.. Literally, the only thing I did between the last, good run and this one was charge the battery and smear some more grease on the pushrods, from the outside...other than that nothing! That's why I'm so puzzled by this.

        The rudder swings freely when not connected, but will go overcenter if swung too far. But the servo won't allow that, I verified that it was not swinging outside of limits. Didn't drive the boat any differently.. it's automatically speed limiting, as the prop will come out of teh water if you get going too fast on the surface and then cavitate. The rudder would disconnect just sitting dockside if I swung it fast enough. No dual rates...
        "It does not take so many words to speak the truth" Chief Joseph

        Comment

        • Bob Gato
          Captain
          • Feb 2019
          • 826

          #5
          Do you know anyone with a gauss meter? -Not being familiar with your Akula's setup...any chance of swapping the connector with a known good one?

          Comment

          • trout
            Admiral
            • Jul 2011
            • 3545

            #6
            The two things that make a standing magnet get weaker is heat and impact (to my limited knowledge), but I do not think it is the issue. To me, it sounds like over travel or binding. Weeds a can accumulate at the pivot points.

            if it continues you can try a stronger connector.
            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

            • Bob Gato
              Captain
              • Feb 2019
              • 826

              #7
              Originally posted by a1965l
              Took the Akula to the neighbor's pond today for some water time. Pre checks good, in the water, worked out the bubbles and got underway. I very quickly lost control of the rudder. Recovering the boat, I find that the rudder is loose, as the magnetic connector has come uncoupled. That happened when I first started running it.. but it was because the pushrod was contacting the driveshaft. I reduced travel and the issue dissapeared. Until today. With the top off, I verified that the linkage was still clear of teh driveshaft, and that there were no other interference issues. I also verified that the WTC was sitting squarely in its foundations and was on the index pin. In the water with the top off, and I find that if I cycle the rudder quickly, it comes disconnected on the pull stroke. Dosen't happen in the air. I've never had an issue with cycling the rudder quickly in the water before, so... what the hell?
              How did you reduce the travel? was it done by an end point change in the transmitter, or was it done by moving a hole on the servo arm?

              Comment

              • a1965l
                Lieutenant Commander
                • Apr 2020
                • 147

                #8
                Reduced the travel in the xmitter. I love computer radios.
                "It does not take so many words to speak the truth" Chief Joseph

                Comment

                • Bob Gato
                  Captain
                  • Feb 2019
                  • 826

                  #9
                  It is imperative that the two magnet faces meet parallel and flat

                  Comment

                  • Kim Sleep
                    Commander
                    • Nov 2013
                    • 329

                    #10
                    What also happens is whatever you are using to be attracted by the magnets becomes a little biot magnetized themselves, and therefore becomes less attracted to the magnet.
                    A man of true Frankenstinean proportions!!

                    Comment

                    • a1965l
                      Lieutenant Commander
                      • Apr 2020
                      • 147

                      #11
                      It's 2 magnets....
                      "It does not take so many words to speak the truth" Chief Joseph

                      Comment

                      • scubaed1911
                        Lieutenant, Junior Grade
                        • Jul 2019
                        • 45

                        #12
                        Originally posted by trout
                        The two things that make a standing magnet get weaker is heat and impact (to my limited knowledge), but I do not think it is the issue. To me, it sounds like over travel or binding. Weeds a can accumulate at the pivot points.

                        if it continues you can try a stronger connector.
                        Hello Trout! You're correct:



                        In the absence of external influences, a commercially viable magnet alloy should remain magnetic for hundreds of years. The alloy’s resulting field may degrade slightly from aging effects, but for the most part it should remain an effective magnetic field source. With that said, most magnets used in real world applications experience many external demagnetizing conditions. A partially demagnetized magnet may greatly impact operational performance that may result in failures in the field...
                        If you're part of the particulate, then you're not part of the solution"

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                        • a1965l
                          Lieutenant Commander
                          • Apr 2020
                          • 147

                          #13
                          I forget who's suggestion it was, but I installed a soda straw over the connectors. Ran today for a while, no issues.
                          "It does not take so many words to speak the truth" Chief Joseph

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