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Question 6DOF: Hexapod vs. "translational gimbal" construction?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Konsta, May 8, 2018.

?

Do you think the "translational gimbal" would work well as a racing sim?

  1. Sound's good, test it!

    100.0%
  2. I can not imagine that (poor description)

    0 vote(s)
    0.0%
  3. I can not imagine that, because of mechanical issues

    0 vote(s)
    0.0%
  4. I can not imagine that, because of software

    0 vote(s)
    0.0%
Multiple votes are allowed.
  1. Konsta

    Konsta New Member

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    Hi everyone,

    i'm a little double-minded about how i should build a 6DOF sim:

    Hexapod:
    pros:
    - "easily" 6DOF's
    - by finding a good geometry it can be optimized for either more translational, rotational or 50/50 traveling/acceleration distances
    - low space requirements
    - low mechanical work amount
    cons:
    - no "permanently" simulated forces, as i will describe below

    "translational gimbal":
    A gimbal will be combined with linear actuators. I like the simulator which a member of xsimulator.net already did (i only find the youtube vid, but i read it somewhen in this forum )

    pros:
    - i would like to use the angles of rotation at least until +/- 90 dregree from center. to be able to simulate force permanently (in racing games for example long straights for accelarating or braking / long curves)
    - "easily" 5 DOF's, (3x rotational, 2x X/Y translational)
    cons:
    - more construction space needed
    - high mechanical work amount
    - difficult heave simulation

    Im sorry that i not yet have any drawings, i will try to hand in later some CAD drafts soon.

    From the ground to the steering wheel, the concept for the translational gimbal would be as described below:

    Base Frame -> X/Y (sway+surge) linear actuated for approx. +/- 250mm -> intermediate frame for pitch (acceleration) gimbal +/- 90° -> intermediate frame for roll gimbal +/- 90° -> intermediate frame for yaw +/- 90° --> racing seat with Z linear actuator (heave) +/- 50 mm

    Simulation concept for Racing Games:
    - In primary, the lateral forces should be simulated by the X/Y/Z translational unit.
    This would be the solution for short-time accelerations.
    - For long-time accelerations, like a long curve or acceleration/braking straight, the pitch/roll could be mixed more and more in addition to use gravitational force by earth (its anyway 1 G to use). Meanwhile, the X/Y will go back to center, i.e. to prepare for braking after a acceleration straight.
    - pitch/roll simulation of the car by suspension can be simulated by the pitch/roll even though.
    - Traction loss will happen by X/Y and Yaw.

    I'm curious about your opinion.
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    In my view a traditional 6DOF Stewart platform can provide a far better range of motion simulation, particularly with respect to heave.

    And when it comes to G-forces neither design will produce anything like the Gs of a F1 or fighter jet, but there are G-force simulation systems, such as the helmet, vest and belt approach @SeatTime has implemented, which can be used in conjunction with traditional motion sim designs.
    • Agree Agree x 2
    • Like Like x 1
    Last edited: May 9, 2018
  3. Konsta

    Konsta New Member

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    Thank you for the hint @noorbeast, this is indeed a well alternative Solution.