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Question All about 2DOF pivot points...

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by clay_statue, Aug 9, 2021.

  1. clay_statue

    clay_statue Intrigued Dilettante

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    So my understanding that for seat movers, the pivot point is more or less centered under your butt with some users favoring slightly fore or aft of the ol' bunghole. Point being that the bullseye for where it should go is reasonably fixed.

    For a fixed frame scenario I am now a firm believer of 3-points of contact vs 4-points of contact because three-points of contact is the best way to define a plane. I read an excellent comment with youtube videos proving their point about the fidelity of motion being superior with a 3-actuator full frame vs 4-actuator full frame. I'd like to link the source but I cannot post external links yet.

    Now that being said you can accomplish three-points of contact with two actuators and the third point-of-contact being a pivot point.

    Let's assume that you could source two actuators with enough force/speed to move a full-frame. Where should the pivot point go? Instinctively one would want to put the pivot under the center of mass so you are largely balanced upon it. This puts the least amount of load on the actuators allowing them to use their speed to improve responsiveness.

    You can do this gimbal style with two nesting planes pivoting perpendicular to each other, as I have seen some users do roughly like this...

    [​IMG]

    Now the issue strikes me that in a vehicle, the pivot point for pitch/roll isn't underneath the driver! The pivot point for roll is down the centerline of the car... beside the driver. The pivot point for pitch would be just behind the driver's seat.

    [​IMG]


    So for an accurate 2DoF full frame experience of pitch/roll would involve an offset position for the pivot point. The clear x's would be actuators/motors and the brown x would be the pivot. I suppose if the pivot was a third actuator that would give you heave as well, but the purposes of this discussion I'm mostly interested in pitch/roll.

    [​IMG]

    Now excluding concerns about the footprint of the this type of setup, would it actually create more realistic pitch/roll forces upon the driver? Or am I just unnecessarily complicating something that won't necessarily translate into a more immersive user experience?

    Disclaimer: I have zero sim rig experience beyond the most basic of FFB wheels. This is all strictly theory I playing with.

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  2. Ads Master

    Ads Master

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