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Rotary 6DOF motor attachment point

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Attyla.pl, Dec 21, 2024 at 12:27.

  1. Attyla.pl

    Attyla.pl Active Member

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    I have a question if the arrangement of the motors in the rotary 6DOF has any meaning as to the platform performance ? ( pitch, roll, heave, sway ) or other parameters ?
    Below two 6DOF rigs to illustrate what I am asking.
    sillenchill  motor mount .jpg ronan motor mount.jpg .
  2. Aerosmith

    Aerosmith Active Member

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    The short answer: yes

    The longer answer could fill books....
    Just the most important considerations:
    • If you don't have weight support (gas springs) the static weight of the rig is the most important reason for motor heating. So if you don't have plenty of motor power (no AASD servos or similar) the most important thing is to keep the static forces low.
    • The higher the angle in the triangle in the picture the higher the static forces are. It has proven that an equilateral triangle (when viewed straight from the rear) is a good compromise.
    attach-points1.jpg
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  3. Aerosmith

    Aerosmith Active Member

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    • The smaller the red triangle the more roll and pitch you get for the same actuator movement while the static forces remain the same. So make it as small as possible without generating collisions with the seat in the extreme positions.
    attach-points2.jpg
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  4. Aerosmith

    Aerosmith Active Member

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    Having crank arms with multiple bore holes is a good idea. This way you can always trade force for speed and stroke if necessary.
    attach-points3.jpg
  5. Attyla.pl

    Attyla.pl Active Member

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    The higher the angle in the triangle in the picture ? attach-points1.jpg
  6. Aerosmith

    Aerosmith Active Member

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    More than 90° for the upper angle in the lowest actuator position is definitely bad. Close to 60° in the lowest position is good. An extremely acute triangle would also be bad because the forces for sway, surge and yaw become extremely high (pushrods almost parallel).
  7. Attyla.pl

    Attyla.pl Active Member

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    I'm ashamed to admit it, but I completely misunderstood your answer :(
  8. Aerosmith

    Aerosmith Active Member

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    And I'm not really sure if I gave the answer you were looking for. Maybe you describe what you are planning to do.
    [​IMG]
    And yes, the red triangle would be better than the yellow if you want to optimize motor load and heating. But the yellow one gives more heave for the same angular arm movement but less force per motor current. There are always pros and cons. If you tell me what the problem is or what you are aiming for then I could hopefully give advice.