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Official Freewing MiG-29 Fulcrum Twin 80mm Thread

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  • Originally posted by kallend View Post

    Here
    Awesome! Thank you soooooo much!

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    • Originally posted by kallend View Post

      Thanks, but I wasn't asking about chokes in the ESC leads (which seem like a good idea). Some people are putting them in the elevator servo leads, and that is what I was wondering about.
      I haven't taken any measurement but it's old 'common knowledge' in the hobby that long wires are more prone to catch EM noise which could disrupt signals.

      I saw it typically on gliders where long wire leads on the wings often were referred to as a cause of problems and many installed ferrite rings to clean the signal, mostly to protect the receiver end.

      The wires reaching the stabs on the MiG-29 are pretty long and pass close to EM sources such as the ESCs. Since the plane was seeing reports of elevator problems early on, I decided it wouldn't hurt to add a couple on the most critical control surfaces to clean the signal of potential noise. In this case, protecting the servo rather than the Rx. I am not claiming the chokes actually helped but it seemed a reasonable addition at a small weight penalty that also helped me move CG aft. :)

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      • I don’t have any and usually remove the ferrite rings that come on ESCs...

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        • Ugh...

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          • Originally posted by Airguardian View Post

            I haven't taken any measurement but it's old 'common knowledge' in the hobby that long wires are more prone to catch EM noise which could disrupt signals.

            I saw it typically on gliders where long wire leads on the wings often were referred to as a cause of problems and many installed ferrite rings to clean the signal, mostly to protect the receiver end.

            The wires reaching the stabs on the MiG-29 are pretty long and pass close to EM sources such as the ESCs. Since the plane was seeing reports of elevator problems early on, I decided it wouldn't hurt to add a couple on the most critical control surfaces to clean the signal of potential noise. In this case, protecting the servo rather than the Rx. I am not claiming the chokes actually helped but it seemed a reasonable addition at a small weight penalty that also helped me move CG aft. :)
            OK, so the choke goes at the receiver end of the long servo wire. I imagine it's a good idea to physically separate the servo leads as far as possible from the ESC power leads too.

            Would be interesting to put a scope on there to see if there really is a problem.

            Comment


            • Originally posted by kallend View Post

              OK, so the choke goes at the receiver end of the long servo wire. I imagine it's a good idea to physically separate the servo leads as far as possible from the ESC power leads too.

              Would be interesting to put a scope on there to see if there really is a problem.
              Someone posted many pages ago the details of how he did this. Quite interesting how he created the alternate pathways to avoid passing near the ESCs.

              Someone else talked about adding metal shielding between the ESCs and servo wiring (I elected to do this because it was easy.). I'm not convinced the metal shielding helps, but I did it anyway. I say that I am not sure it helps because there is no way to ground it.

              I used aluminum metal pipe wrap tape. The servo wires run in a foam channel on the other side of the metal tape.

              Click image for larger version  Name:	MiG-29.jpg Views:	0 Size:	58.3 KB ID:	312207

              -GG

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              • Ferrite Rings on ESC's: What Do They Do and How Can You Use Them? - RC Heli Nation (rchn.org)

                Bottom-line up-front: The common-mode noise frequency is unlikely to affect 2.4 GHz receiver - lower-frequency noise with outrunner kV's, and pretty narrow-band with inrunner kV's vs wide-band noise-robustness of spread-spectrum systems.

                It's not the wires from the ESC to the motors that could potentially act as a noise-radiating antenna - it's the cable running from the ESC to the receiver. The servos control signals are more likely to be impacted by this noise at certain throttle settings.

                You can introduce some distance from the ESC wire, reducing coupling, by separating and bundling the servo cables together with a cable tie and attaching to the fuselage wall with a mount. Or you could use metal foil tape to tape down the ESC wire. The ESC's heat sink/plate provides some shielding, too - as long as the wires are on the heatsink side, not any exposed electronics.

                The article also mentions "OPTO" ESCs (without built-in BEC's) are optically coupled, so no power is transmitted back from the motor-driving circuit back to the controller, hence they often don't have the ferrite rings.
                Last edited by fredmdbud; May 10, 2021, 04:40 AM.

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                • Originally posted by fredmdbud View Post
                  Ferrite Rings on ESC's: What Do They Do and How Can You Use Them? - RC Heli Nation (rchn.org)

                  Bottom-line up-front: The common-mode noise frequency is unlikely to affect 2.4 GHz receiver - lower noise frequency with outrunner kV's, and pretty narrow-band with inrunner kV's vs wide-band noise-resistance of spread-spectrum systems.

                  .
                  No mention of putting chokes on servo wires in that article.

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                  • Originally posted by kallend View Post

                    No mention of putting chokes on servo wires in that article.
                    Whatever wires are powering the receiver (THRO cable for ESC w/built-in BEC, voltage supply wires to receiver for discrete BECs) - but not wires driving the servos, yeah.

                    That be low-pass filtering each susceptible cable, instead of just the radiating one. But if you got the rings, and the space, have at it ...

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                    • It’s a risk/reward choice for each individual. Simple as that.

                      For a few dollars and very little effort and a VERY slight weight addition, I went from 3 loss of control events to ZERO! And that’s ZERO with several thousands of flights. That’s all the theory I need.

                      For a “rare” event (RF noise induced crash), I might have so far just been lucky in these crash free thousands of flights. Could be I am about to have a loss of control event/crash any time even with chokes installed. But, my bet is...again based on my personal experience and I could be totally wrong...that I have improved my system stability. Read....I am not experiencing loss of control any more.

                      Paraphrasing a historical phrase: “Ya plunks down your nickel and ya takes your choice.”

                      Me....I much prefer flying without crashing. Especially 100 mph+ birds. Peace of mind thing for me.

                      If it is a long wire, have at it. Couldn’t hurt. Someone posted that his electronics instructor said, “If in doubt, choke it out.”

                      -GG

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                      • Originally posted by kallend View Post
                        Would be interesting to put a scope on there to see if there really is a problem.
                        Agree, but don't have any... and am a bit lazy!

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                        • Originally posted by GliderGuy View Post
                          It’s a risk/reward choice for each individual. Simple as that.

                          For a few dollars and very little effort and a VERY slight weight addition, I went from 3 loss of control events to ZERO! And that’s ZERO with several thousands of flights. That’s all the theory I need.



                          -GG
                          Reminds me of the very old joke:

                          A man is sprinkling a powder all over the streets, when a policeman walks up to him and asks what on earth he is doing. The man replies, saying "keeping the elephants away of course! It's elephant repellent."

                          The officer replies, don't be absurd, there are no elephants here. The man replies "then it must be working!"


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                          • Too true! But Hugh said he is monitoring data post flights made with chokes, and he is seeing positive results (no frame drops, etc.). Might actually be better than just powder! And a key difference is I saw elephants...applied powder...and no longer see elephants.

                            Hugh??? Care to elaborate?

                            Also....might be best to move this discussion to the radio and receivers forum. MiG pilots may be about ready to arm their missiles. LOL

                            -GG

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                            • Originally posted by GliderGuy View Post
                              And a key difference is I saw elephants...applied powder...and no longer see elephants.
                              Correlation does not imply causality (the science/logical guy in me says...).
                              But the 'practical engineer' one replies: sometimes, it's just easier to apply 'reasonable' fixes (The anti-elephant powerd wouldn't be the best analogy though, lol) as long as they don't require big trade-offs and call it a day. :)

                              So, I won't state that these chokes are solving anything but I will keep mine in place for a lack of better understanding and a reluctance to invest the time/money it'd require to get everything right and more deeply understood.

                              Comment


                              • Originally posted by Airguardian View Post

                                Correlation does not imply causality (the science/logical guy in me says...).
                                But the 'practical engineer' one replies: sometimes, it's just easier to apply 'reasonable' fixes (The anti-elephant powerd wouldn't be the best analogy though, lol) as long as they don't require big trade-offs and call it a day. :)

                                So, I won't state that these chokes are solving anything but I will keep mine in place for a lack of better understanding and a reluctance to invest the time/money it'd require to get everything right and more deeply understood.
                                I'm a firm believer in chokes in the receiver to ESC lead if that lead is supplying the + supply to the Rx.

                                I've seen no evidence whatsoever presented for a benefit of chokes in the servo leads. Elephant repellent but harmless if it makes you feel better!

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                                • Originally posted by GliderGuy View Post
                                  And a key difference is I saw elephants...applied powder...and no longer see elephants.
                                  Nothing wrong with that. Then there are ostriches. I've seen ostriches but never one with its head in the sand. Apparently, they don't do that. However, if you believe that ostriches stick their heads in the sand when scared, then it doesn't hurt to keep that in your "happy thoughts". Since most people on earth will never see an ostrich in the wild, there's no way to disprove it. Just don't try to scare one when you do see one.

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                                  • Originally posted by kallend View Post
                                    I've seen no evidence whatsoever presented for a benefit of chokes in the servo leads. Elephant repellent but harmless if it makes you feel better!
                                    Placebo effect is REAL.
                                    It affects your faith, and your faith affects your LUCK.

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                                    • When you get right down to it, of the 16 modifications I did (to date) on the MiG, many were very likely not necessary. They were mostly easy to do, rainy/windy day projects and somewhat inexpensive to implement.

                                      Remember...we were dealing with the unknown, and somewhat grasping at straws = any straws.

                                      But we kept them flying!

                                      Mine finally developed too much toe out. Was looking ugly and was hard to roll. So, I applied a hammer and vice to the main gear axles. Red neck mod, but it did the trick.

                                      Airguardian, so far my “fix” to the main gear blocks is holding up = CF, metal angle bracket brace, and more Foam Tac added around the blocks. Will be surprised if more work than this is needed.

                                      -GG

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                                      • My MiG-29 arrived today. Here’s a short video on what the upgraded parts look like.
                                         

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                                        • Originally posted by GliderGuy View Post
                                          Airguardian, so far my “fix” to the main gear blocks is holding up = CF, metal angle bracket brace, and more Foam Tac added around the blocks. Will be surprised if more work than this is needed.
                                          Good to know!
                                          Mine is holding well too.
                                          (I glued a balsa wood square-rod to distribute loads against the side wall of the duct).

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