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The curious case of T-Rex600 servo horns.

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  • The curious case of T-Rex600 servo horns.

    I bought this 600E second hand a month or two ago and it has bee working absolutely fine. It is my favourite non-scale machine of the five I have, of which two are scale machines.

    All has been going well until the other day when it rolled over on spool up for some unexplained reason. This suggested a servo failure, even though control response had been checked immediately before spooling up. In the re-build, not that there was a great deal of damage - just boom-strike and blades - I focused on the servos and, to my surprise found that the controls were binding on the two forward servos, aileron and pitch. The binding was occuring between the two parallel push rods going rearward from the servo and the 'returning' horn which is connected via push rod to the swash-plate, running betwen the servo push-rods and the frame. I was surprised because this had neither shown on control checks or in flying but, it obviously needed attending to. On one servo, with dual arms for the 'horns', this was easily done by positioning the balls on the outside instead of the inside. This is consistent with the illustration in the T-Rex 600 manual.

    The other servo has an Align disc type servo arm which can only take the balls on the inside because it has a captive nut location on the outside. This is consistent with most (if not all) of the illustraions (Google, suppliers etc) for Align servo arms. With this one the end of the inside horn was contacting the end of the plastic ball link ring and so just had to carefully file a 45 degree bevel on the end of it to give the clearance.

    All rather curious with conflicting information coming from the manual and spare parts supply. So what comments do other T-Rex600 owners have on this please.

    Regards

    Nigel

  • #2
    Check the Ball link size on the servo disc I found on one of mine that the larger size ball had been fitted causing the link to be tight on the ball and this caused it to bind and be very notchy.
    - TREX 600esp - TREX 600e - TREX 450 Sport - Eflite Blade MCPX - Eflite Blade MSR -


    - DX7SE - DX9ii - Pheonix -


    * Loads of Gear & Still No Idea *

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    • #3
      Originally posted by BiG-T View Post
      Check the Ball link size on the servo disc I found on one of mine that the larger size ball had been fitted causing the link to be tight on the ball and this caused it to bind and be very notchy.
      Many thanks, Big-T, will check that.

      Nigel

      Comment


      • #4
        Check the horns are correct for the servo.

        Align/Futaba horns have an "F" on them and JR have a "J".

        I fitted jr servo wheel to align servo once and it's a tight fit but can spin on splines under load.





        Sent from my iPhone using Tapatalk
        Mike
        www.RC-Scotland.com

        T-Rex 700G G270 DS610s GP750/DS650
        TZ Frenzy .53 Red Line
        T-Rex 600 .52 ASP
        T-Rex 600 .80 ASP 4ST

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        • #5
          Thanks, Mike. Appreciated.

          Nigel

          Comment


          • #6
            The Align disc horns are not meant for the 600E(old style) as the balls need to be on the outside of the horns which you cant do on the discs.

            Comment


            • #7
              I just re-read your post now that im on my laptop.

              I have had issues with the 600 and servo horns/rod linkages.
              Im currently building one for a scale body and I too had issues with ball links and the discs.

              I have chucked the discs and using standard arms with the ball links pointing away from the heli, this is because the linkage was at an angle and binding on the disc, now they run parallel with the frame and all is good.

              I think this is because the manual is designed for "Align" servos which have a different profile to the ones Im using.

              Next battle is the exhaust.
              Mike
              www.RC-Scotland.com

              T-Rex 700G G270 DS610s GP750/DS650
              TZ Frenzy .53 Red Line
              T-Rex 600 .52 ASP
              T-Rex 600 .80 ASP 4ST

              Comment


              • #8
                Originally posted by ChrisB View Post
                The Align disc horns are not meant for the 600E(old style) as the balls need to be on the outside of the horns which you cant do on the discs.
                Thanks, Chris. Noted. But it is still intersting that if, for example, one Googles 'T-Rex 600E servo horns', almost only the disc option is shown. Mike, your comments are also interesting in that respect. Servos on this one are Spektrum DS821s, so what I obviously need to do is get Spektrum servo horns.

                Comment


                • #9
                  The original 600E(not the newer esp) was long before Align released their own horns,servos,gyros etc.

                  The servos require the balls to be on the outside and of course the discs only accomodate inside mounting of the ball.

                  Not sure about the ESP though as never owned one,that may have altered slightly as it was much later in production.

                  FWIW i rate the Align wheels as bordering on rubbish as the splines are very easy to strip,had it happen to mine when i used them and seen countless others do it.
                  Last edited by ChrisB; 04-06-2011, 12:19 PM.

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                  • #10
                    Many thanks, Chris. Noted. Very helpful

                    Nigel

                    Comment


                    • #11
                      Originally posted by RotaryOne View Post
                      Thanks, Chris. Noted. But it is still intersting that if, for example, one Googles 'T-Rex 600E servo horns', almost only the disc option is shown. Mike, your comments are also interesting in that respect. Servos on this one are Spektrum DS821s, so what I obviously need to do is get Spektrum servo horns.

                      DS821s are Futaba/Align splines.

                      Other option are the quickuk metal wheels as they do not have a recess for a nut and ball link can be mounted on either side.

                      Originally posted by ChrisB View Post
                      The original 600E(not the newer esp) was long before Align released their own horns,servos,gyros etc.

                      The servos require the balls to be on the outside and of course the discs only accomodate inside mounting of the ball.

                      Not sure about the ESP though as never owned one,that may have altered slightly as it was much later in production.

                      FWIW i rate the Align wheels as bordering on rubbish as the splines are very easy to strip,had it happen to mine when i used them and seen countless others do it.

                      Align plastic wheels stripped on my 700Gasser.
                      Last edited by maderdog_1024; 04-06-2011, 06:01 PM.
                      Mike
                      www.RC-Scotland.com

                      T-Rex 700G G270 DS610s GP750/DS650
                      TZ Frenzy .53 Red Line
                      T-Rex 600 .52 ASP
                      T-Rex 600 .80 ASP 4ST

                      Comment


                      • #12
                        Originally posted by maderdog_1024 View Post
                        DS821s are Futaba/Align splines.

                        Other option are the quickuk metal wheels as they do not have a recess for a nut and ball link can be mounted on either side.
                        Thanks, Mike. Very helpful. Will work with that.

                        Nigel

                        Comment


                        • #13
                          UPDATE: It now transpires that the Spektrum DS821 servos (which came with the machine) are not considered at all suitable for helis by a key Midland supplier. The suggestion is that the plastic gears are not man enough for a 600 machine. Another suggestion is that those servos are also vulnerable to vibration. I have one spare Futaba S3050 and could get some more of those.

                          What is anyone else's opinion please?

                          Nigel

                          Comment


                          • #14
                            Hi Nigel check here for servo's info etc www.servoshop.co.uk just looked up your DS821's and they say 'Not recommended for helicopter use or installations subject to high vibration' I run Futaba 3050's on 1 600 cyclics & 9254 on the tail and I have just finished a 600 esc and fitted 9255's on the cyclic's & 9254 on the tail (got the 3 9255's off a guy on the BMFA took them off his Nitro as they pulled too much power & he didn't want to fit a bigger Lipo & BEC.)

                            Tony
                            - TREX 600esp - TREX 600e - TREX 450 Sport - Eflite Blade MCPX - Eflite Blade MSR -


                            - DX7SE - DX9ii - Pheonix -


                            * Loads of Gear & Still No Idea *

                            Comment


                            • #15
                              Great stuff, Tony. Many thanks.

                              Nigel

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