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Looking for optimal pivot location for seat flaps of G-Seat

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by MarkusB, May 3, 2016.

  1. MarkusB

    MarkusB Active Member Gold Contributor

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    Dear All,

    I did not know anything about G-Seats before reading @RiftFlyer's thread, and during the past days I have looked around quite a bit and found several amazing projects.
    Since I am now considering to add seat flaps to my (still not existing) 2DOF simulator for adding "heave", I focused on these flaps and found different approaches regarding their pivots.

    The following sketch shows three possible locations for the pivots of the flaps on which you are sitting (not the ones on the back rest).
    G-Seat_Pivots.jpg

    Since the pivot location obviously has an essential impact on where the pressure is applied to butt and legs, my question is: Do you have any recommendation where to place the pivot? As I mentioned above, I have seen these variations during my Internet search:
    • inner edge of the flaps
    • about 30% away from the inner edge
    • outer edge

    Thanks a lot and best regards,
    Markus
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  3. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    When I asked myself this very question, I thought case B would give more information: over-pressure and under-pressure

    920836palettegSeat.png
    but still not tested yet...

    Attached Files:

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  4. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    I've yet to tackle the base of my seat but from research I believe option two is the best (30%).

    The critical thing is where that pivot point is relative to your butt. You want to sink slightly as the flaps are raised. That means the pivot point can't be directly under you but should be towards the outside.

    Option 3 places all of your weight on the flap and will likely see much higher amp draw. For example, I'm not sure how wiper motors would cope with that arrangement.

    Option 1 works well for racers as it provides more lateral force (raising one side and lowering the other). I'm not sure how well it would represent heave though and the effect it provides you will already get from your 2dof setup.

    I hope that's of some use.
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  5. MarkusB

    MarkusB Active Member Gold Contributor

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    @RacingMat & @RiftFlyer: Thanks a lot for your informative and helpful replies!

    My gut feeling is also that option 2 is the one to start with.

    About "heave": Actually I think that the flaps will add an additional effect to the 2DOF sim, because what I already have is only pitch and roll. My idea is to add the "heave" DOF by moving the seat flaps synchronously, and ideally with only one motor. (I have rather strong ones.) I am already thinking of the mechanics.
  6. SeatTime

    SeatTime Well-Known Member

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    Maybe have a look at the GS4 for inspiration.
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  7. SeatTime

    SeatTime Well-Known Member

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    I also implemented 'heave' with a single front hinged flap on my old rig. You can just see it (look under the seat) moving up and down in this video.

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  8. MarkusB

    MarkusB Active Member Gold Contributor

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    Thanks for the videos, @SeatTime! Interesting. Seems that the GS4 seat also has the pivots near the inner edge, but not quite at the edge.

    Another aspect: I saw the seat belts in your own video. It looks like they are mounted behind the seat, so that they automatically release when the seat pitches backward (acceletation) and tighten when it pitches or forward (brake), similar to some G-Seat mechanics I saw. I guess this is intended? If so, great idea. :)
  9. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Another option to consider is a fabric seat base and rollers. I've heard of it from a member on dcs forum. Not implemented yet but the idea is intriguing I think.

    At full deflection the fabric is taught and as the rollers spin the fabric slackens causing you to sink in the seat. Imagine the fishing/camping type folding chairs as an example. Only a small amount of movement is needed.
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  10. MarkusB

    MarkusB Active Member Gold Contributor

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    Yes, this also sounds interesting. But I guess that the fabric will not cause as much pressure to butt & legs as rigid flaps because the fabric will align itself to the shape of your body. Just an assumption, so I may be wrong.
  11. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    You are correct I think this option is less about pressure and more about the sudden rise and fall in the seat which if fast enough could replicate that feeling we get in our stomach going over a bump.
  12. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    I think it's probably much more comfortable :)
    and rather easy (rotating a tube to wind the fabric)
    good idea!
  13. MarkusB

    MarkusB Active Member Gold Contributor

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    Agreed that it may be easier to realize, although the motor would probably need more power because it would have to lift your butt instead of only squeezing it (depending again on the position of the pivot).
    But let me bring up another aspect:

    What I immediately loved when reading about the G-Seat concept with its rigid flaps is that all the forces are applied as long as the corresponding acceleration lasts within the game, and not just for the fraction of a second.
    For example: When raising the seat flaps for simulating the heave DOF, the pressure is applied to the body until the flaps are lowered again, which means until the "heave" acceleration within the game software ends (or may even be reversed).

    In contrast to this, the fabric approach seems to apply the heave force only for the moment in which the fabric tightens, although the acceleration within the game may still continue.

    This is also true for usual 6DOF simulators: There are permanently applied forces for roll and pitch, and there are temporary applied forces for yaw, heave, surge, and sway. (Except you simulate surge and sway via pitch and roll).

    My hope with the rigid flaps is that having a permanent heave force would be a benefit compared to the temporary force that is applied with other approaches, including the one with the fabric. For example, you would not need to slowly untighten the fabric again just for being ready for the next heave movement. Instead, you just keep the rigid flaps tightened until heave ends.

    However, these are just my theoretical thoughts without any practical evidence. So please feel free to share your experiences. (I guess there may already be related threads in this forum. In this case I would be glad about getting some links.)

    Thanks,
    Markus
  14. SeatTime

    SeatTime Well-Known Member

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    My approach is slight different, designed from the beginning as a enhancement to a motion simulator, not something that would be used in isolation. The advantage of this is that the power requirements can be lower, allowing lighter and cheaper components to be used. From my experience, if you want to dead lift a rider than you going to need a good amount of power/torque which is usually neither light, or cheap.
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  15. MarkusB

    MarkusB Active Member Gold Contributor

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    Yes, I completely agree. I guess our approaches are quite similar. I will also use the flaps at the bottom of the seat as an add-on to my 2DOF seat mover. The only difference is that I have built a pair of flaps instead of your single front-hinged flap, similar to a standard G-Seat. But since I only want the flaps to apply the "heave" force, I plan to move them synchronously with only one motor. I have posted some details here:
    https://www.xsimulator.net/communit...ation-for-oculus-rift.7684/page-3#post-115608

    In addition, I plan to have a pair of belts that move along the backrest and cause some friction on the back of my shirt. The idea is the following: When the belts move up, I get the feeling to get pressed down into the seat, and when the belts move down it feels like I am lifted upwards. This belt movement will be synchronized with the flaps. I came to this idea during my last (real) flight, when I sensed the up/down movement on my back in this way. I did not read about it though, and thus I don't know if it will work as expected.
  16. SeatTime

    SeatTime Well-Known Member

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    I think you are talking about the heave module I had installed in my old sim :). FI, I'm actually installing a servo driven Gseat into my current 6DOF. Quite different requirements and therefore design.
  17. MarkusB

    MarkusB Active Member Gold Contributor

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    Yes, correct: I was talking about your heave module that you mentioned earlier in this thread.
    Wow, a 6DOF rig including a G-Seat sounds really exciting and seems to be the most comprehensive rig I can imagine. :)
    Did you post anything so far? I found your 6DOF thread, but it still seems to have a normal racing seat mounted.
  18. SeatTime

    SeatTime Well-Known Member

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    I have the parts, completed some bench software/hardware tests, just need to find the time to start putting all the pieces together into the seat. Its not quite like your normal Gseat. Still pretty much an experiment, so haven't posted much yet.
  19. MarkusB

    MarkusB Active Member Gold Contributor

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    Sounds very interesting! I have started watching your thread for not missing anything. :)