flex vibration

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  • Rumdog
    Fast Electric Addict!
    • Mar 2009
    • 6453

    #1

    flex vibration

    I have a 34" sprintcat. Running 5s2p, feigao 580L 1649 kv. Anyhow, the longest section of the stuffing tube extends from the hull towards the strut. It ends about3/16" before the strut. The strut is a bearing style strut. When bench testing, ( simply blipping the throttle), I notice quite a bit of vibration in this area of the tube. How can I get rid of this, being that there is so much unsupported tube? It is .187 flex, running linerless k@s brass.
  • domwilson
    Moderator
    • Apr 2007
    • 4408

    #2
    Got any pics?
    Government Moto:
    "Why fix it? Blame someone else for breaking it."

    Comment

    • detox
      Fast Electric Addict!
      • Jun 2008
      • 2318

      #3
      Here is a couple of things you can try:

      Check your collet. It may be out of round or balance. To check...simply spin your motor in hand with collet attached. I have two of the Octura .187 collets and only one of them is in balance

      OSE recommends using 7/32" brass tubing with .187 cable.

      Try a slight S bend on your stuffing tube or crimp your stuffing tube slightly every 2 inches to reduce harmonics.

      Use lots of grease.

      Read here; http://forums.offshoreelectrics.com/...ad.php?t=11896


      ...

      Comment

      • Rumdog
        Fast Electric Addict!
        • Mar 2009
        • 6453

        #4
        pics

        here ya go...
        Attached Files

        Comment

        • domwilson
          Moderator
          • Apr 2007
          • 4408

          #5
          Is it the pic or is that tube not aligned with the strut? Maybe a small piece of teflon liner from the stuffing tube to the strut?
          Government Moto:
          "Why fix it? Blame someone else for breaking it."

          Comment

          • Rumdog
            Fast Electric Addict!
            • Mar 2009
            • 6453

            #6
            It's the pic. I'm running linerless. There is no room to go into the strut with teflon or the brass. I like the idea of the S bend but I may have to adjust my motor angle to raise the motor shaft a bit, or just put a much more aggresive type bend in it. My collet runs true and is balanced pretty well it seems.

            Comment

            • detox
              Fast Electric Addict!
              • Jun 2008
              • 2318

              #7
              It's hard to see in picture, but you should have used the next size larger tubing epoxied to your hull. That way you can remove your stuffing tube from hull without having to cut it away from hull and cured epoxy. I would cut that out and re-do.


              ...

              Comment

              • Rumdog
                Fast Electric Addict!
                • Mar 2009
                • 6453

                #8
                how would you go about supporting the tube then?

                Comment

                • detox
                  Fast Electric Addict!
                  • Jun 2008
                  • 2318

                  #9
                  KS brass tubing is telescopic. Meaning the next larger size is a tight slip fit. If using a 1/4" or 7/32" stuffing tube use the next larger size epoxied to hull (short piece). That way your stuffing tube can be easily replaced. A slightly sharp bend or S bend will prevent tube from rotating while cable is spinning.

                  Comment

                  • m4a1usr
                    Fast Electric Addict
                    • Nov 2009
                    • 2038

                    #10
                    Take your flex assy out and put it on a flat surface. Clean it well prior to. Roll it back and forth with your fingers where the rigid shaft is silver soldered to the flex, observe how well it was centered when soldered. You would be amazed at how many folks dont do the one simple check. It was probably misaligned when soldered, more common then you think from name brand sources. It will be appearent right away if its not properly centered. And its a huge source of power robbing friction.

                    A better method is to chuck up the rigid part in a drill press and spin it up. You can immediately see an out of tolerance solder/ misalignment job.

                    John
                    Change is the one Constant

                    Comment

                    • Rumdog
                      Fast Electric Addict!
                      • Mar 2009
                      • 6453

                      #11
                      I'm likin' these ideas guys!

                      Comment

                      • domwilson
                        Moderator
                        • Apr 2007
                        • 4408

                        #12
                        Originally posted by m4a1usr
                        Take your flex assy out and put it on a flat surface. Clean it well prior to. Roll it back and forth with your fingers where the rigid shaft is silver soldered to the flex, observe how well it was centered when soldered. You would be amazed at how many folks dont do the one simple check. It was probably misaligned when soldered, more common then you think from name brand sources. It will be appearent right away if its not properly centered. And its a huge source of power robbing friction.

                        A better method is to chuck up the rigid part in a drill press and spin it up. You can immediately see an out of tolerance solder/ misalignment job.

                        John
                        I agree. That would explain why the tube looks misaligned with the strut.
                        Government Moto:
                        "Why fix it? Blame someone else for breaking it."

                        Comment

                        • Jeff Wohlt
                          Fast Electric Addict!
                          • Jan 2008
                          • 2716

                          #13
                          Sure looks like too small of a stuffing tube but hard to see in the pic.

                          Is the shaft soldered or loctited in the stub? I had a long flex on a hydro that slapped a bit but when under load in the water it was nothing.
                          www.rcraceboat.com

                          [email protected]

                          Comment

                          • andym
                            More Go Than Show Prop Co
                            • Apr 2007
                            • 2406

                            #14
                            Most struts have a nose piece on them that your tube slides into, the fact that it is unsupported by the strut will cause many a problem. Any harmonic or balance related flexing will move the tube about instead of the tube limiting them. The tube is to small ID as Jeff stated as well. See if you can get a strut only { no mount=cheaper) with the nose and replace the stuffing tube. If you heat the epoxy with a hair dryer it will peal away easily.

                            Comment

                            • detox
                              Fast Electric Addict!
                              • Jun 2008
                              • 2318

                              #15
                              Originally posted by andym
                              Most struts have a nose piece on them that your tube slides into, the fact that it is unsupported by the strut will cause many a problem. Any harmonic or balance related flexing will move the tube about instead of the tube limiting them. The tube is to small ID as Jeff stated as well. See if you can get a strut only { no mount=cheaper) with the nose and replace the stuffing tube. If you heat the epoxy with a hair dryer it will peal away easily.
                              Verygood observation. It does look like stuffing tube and cable is unsupported at strut. What happened to this strut? Was tapered section cut off?

                              Comment

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