How to correctly move T-Rex 450 Cyclic Servos

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14 May 2014 21:17 - 14 May 2014 21:41 #23237 by i812
I would like learn (over the phone?) how to configure a Deviated Devo8S to properly control the three Cyclic Servos on a new build T-Rex 450 with Flybar and 6 Channel DSM2 RX.

I'm in the process of building/setting-up my first "3 Servo, 120 degree" Swashplate type heli, and don't know how to configure the TX so all 3 Cyclic Servos move correctly according to TX Throttle/Pitch, AIL, and ELE stick movements.

I've watched a (Finless Bob) How to Video, and read the Deviated Devo 8S User Manual, and both recommend to:
  1. Verify Model Menu's, Swash submenu, "SwashType" has "3Servo 120" selected.

  2. Move the TX's Throttle/Pitch Stick Up/Down and verify all 3 Cyclic Servos move the Swashplate Up/Down accordingly - if any of the Cyclic Servos don't move in the proper direction, then that Servo should be "REVERSED" in the Model Menu's, "Reverse" submenu.

  3. NOTE: I've successfully completed above procedure. Originally, when I moved my TX's Throttle/Pitch stick upward, only two Cyclic Servos (Rear/EL and Front-Left/AIL Servos) moved the Swasplate upwards, but one (Front-Right/Pitch) Servo moved the Swashplate downward. I used the Deviation's Model Menu - Reverse submenu to change the 6-PIT setting from Normal to Reverse, then verified all 3 Cyclic Servos move the Swashplate Up/Down according to TX Throttle/Pitch Stick movement.

  4. Move the TX's EL/AIL stick forward/backward and verify the back (EL) Servo moves the Swashplate upward, and both front (AIL and PIT) Servos move downward - if not, then use the Model Menu's, Model Setup, Model Type - Helicopter submenu to change the appropriate ELE Inv, AIL Inv, and/or COL Inv settings from Normal to Inverted as required.

    NOTE: When I move my TX's EL stick forward:

    rear (ELE) Servo moves Swashplate upward
    front-left (AIL) Servo moves Swashplate downward
    front-right (PIT) Servo moves Swashplate upward < this is incorrect, it should be downward

  5. Move TX's AIL stock right/left, and verify the back EL Servo doesn't move, and both front Servos make the Swasplate move accordingly - if not, then use the Model Menu's, Model Setup, Model Type - Helicopter submenu to change the appropriate ELE Inv, AIL Inv, and/or COL Inv settings from Normal to Inverted as required.

    NOTE: When I move my TX's AIL stick right:

    rear (ELE) Servo moves Swashplate downward < this is incorrect, it should be stationary
    front-left (AIL) Servo moves Swashplate stationary < this is incorrect, it should move upward
    front-right (PIT) Servo moves Swashplate upward < this is incorrect, it should move downward

    AFAIK, the solutions to the example incorrect Servo problems shown in the Finless Bob 450 Build video and Deviation 8S User Manual are obvious; however, it's not obvious to me what needs to be changed on my TX to correct my above incorrect Cyclic Servo movements.

    Sorry for the long post, I can't think of a better way to post the pertinent info using fewer words.
Last edit: 14 May 2014 21:41 by i812.

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10 Feb 2015 11:27 #28538 by trhodes
Replied by trhodes on topic How to correctly move T-Rex 450 Cyclic Servos
Did you ever get this problem solved. My swash is doing something similar and I can't figure it out.

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11 Feb 2015 17:30 #28571 by mikemacwillie
Replied by mikemacwillie on topic How to correctly move T-Rex 450 Cyclic Servos
It's most likely caused by a combination of the servos being plugged into the wrong channels/mixer channel assignments, and channel reversal.

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