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Question 3DOF gimbal flight simulator YAW 360

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by yassine.eal, Jan 1, 2026.

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  1. yassine.eal

    yassine.eal New Member

    Joined:
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    My Motion Simulator:
    3DOF, Arduino
    Hi everyone,

    I’m starting a DIY 3DOF motion flight simulator and I’d love some advice from people who have already built gimbal-style rigs—especially on how you handled CG and axis placement.

    Project goal / architecture

    • Full-size seat platform for X-Plane/MSFS/DCS World. VR mandatory

    • 3-axis gimbal stack:
      1. Yaw at the base (vertical axis) with 360° continuous rotation (slip ring planned)

      2. Pitch frame mounted on yaw frame

      3. Roll frame mounted on pitch frame carrying the cockpit (seat + pedals + joystick + throttle + monitor support)
    • Structure planned in welded steel.
    Where I am now (CAD / mass model)

    • I’m working CAD-first in Onshape with “envelope volumes” + proxy masses to estimate the center of gravity.

    • Current proxy payload is ~159 kg (including a 110 kg pilot equivalent + seat/pedals/monitor/support envelopes).

    • I placed the cockpit geometry based on ergonomics

    • With my current assumptions, the overall COM relative to the pilot torso reference is roughly:
      • X ≈ 0 mm (symmetry)

      • Y ≈ +151 mm (forward)

      • Z ≈ −54 mm (below)
    I know this COM is only as good as the assumptions (monitor/support mass, future steel structure mass, adding throttle/joystick mounts, panels, cabling, etc.), so I’m trying to understand the best workflow used by experienced builders.

    What I’m asking

    1. When did you finalize CG and axis placement?
      • Did you lock it during CAD/design, or after the chassis/cockpit was physically assembled and you measured the real CG?
    2. How did you choose where the pitch/roll axes intersect?
      • Did you aim for the intersection to pass through the CG at neutral position?

      • How much CG error did you tolerate before it became problematic (motor torque, stability, oscillations)?
    3. What practical methods did you use to measure CG in real life once the cockpit was assembled (weighing corners, balancing, etc.)?

    4. Any common mistakes to avoid with gimbal rigs (especially with a front monitor on the moving frame and 360° yaw)?

    5. And finally, do you have any resources, advices, tutoriels on the building of a 3DOF with 360° axes ? (only for yaw for the moment)
    If you have any build logs, photos, or rules-of-thumb that helped you place axes and manage CG drift as you added components, I’d really appreciate it.

    Thanks a lot!
    Yassine
    yassine.eal, Jan 1, 2026
    #1