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Seat Harness Braking Pressure – Pneumatic, Belt Tensioning, or Both?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by BlazinH, Feb 2, 2019.

  1. BlazinH

    BlazinH Well-Known Member SimTools 2.0 Beta Tester

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    I would like to ask your opinion on which system you believe would be the most effective in simulating braking pressure; pneumatic air bladders that apply pressure directly to the front of the chest, a system that pulls on the shoulder belts thereby applying pressure on the chest, or both?
    Last edited: Feb 2, 2019
  2. BlazinH

    BlazinH Well-Known Member SimTools 2.0 Beta Tester

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    My thinking is that using pneumatic bladders instead of pulling on the belts to apply chest pressure you can design a system that doesn’t pull you into the seat back too which is opposite of what actually happens.
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  3. joe extraknow

    joe extraknow Member Gold Contributor

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    Good thought. I will keep my tensionner, probably add air pressure bladders at front of chest. I have the sparco evo seat (small). The tensionner mainly pull the force upon my shoulder.
  4. BlazinH

    BlazinH Well-Known Member SimTools 2.0 Beta Tester

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    One issue to consider is Newtons 3rd law that states every action has an equal and opposite reaction. Air bladders can exert over 100 pounds of force but half the force will be exerted in the opposite direction. So the challenge is how to keep from loosing that much. Putting them between your chest and shoulder belts for example would help accomplish this. However keep in mind the extra stress that will be put on a powered harness tensioner may cause its motor(s) to burn out prematurely. It will also likely be less effective.
  5. joe extraknow

    joe extraknow Member Gold Contributor

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    Yes, like a g-seat, it works because of Newton's 3rd law. I guess I don't need that much powerful air bladder. Maybe a RC servo one.
    I did quick tests with my tensioner

    1. Stationery, no motion: the pulling force tactile on my shoulder feels strange and awkward as my body in stationery. I don't think I will use it on a non-motion rig.

    2. Motion, chassis mover with d-box style (4 inch actuators) with max pitch angle < 3.5 degree: similar feel as above.

    3. Motion, seat mover: much better feel.

    I think in order to have a tensione type or air bladder type or combination of both to work effectively, my body needs to lean forward in certain degrees while braking.
    I will think adding air bladder in front of chest would enhance an immersion.
    Last edited: Feb 9, 2019
  6. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    I have tried them all and still use my G-vest system in my own sim. Feels the most natural, as it can pull on the body in many direction like gravity would do and can apply high pressure evenly to the multiple sides of the chest. Unfortunately for it to work correctly, it requires a purpose built support frame, which is one of the reasons that I moved to a fiberglass shell. See image below - note the shoulder straps are also driven.

    20190210_074042.jpg
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  7. joe extraknow

    joe extraknow Member Gold Contributor

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    The vast looks great, but the cable system seems pretty complicate.....as shown. Why don't you use air bladders for your vast, instead?

    Btw, the vast could tighten your body, leaves no room for moving. Do you intend to apply this type design for F1 car seating, rather than GT car?
    Last edited: Feb 10, 2019
  8. BlazinH

    BlazinH Well-Known Member SimTools 2.0 Beta Tester

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    Its more immersive when using a complete system meaning that when using air bladders for braking force on the chest then it works best to also use them for acceleration force on the back. This makes the forces perfectly oppose each other and thereby is easy to accept both forces as accurate representations of each.

    I thought about also using a cable that pulls forward to compliment the air bladders but haven't come up with a solution that doesn't cause obstruction. How does your implementation work out for you @SeatTime? I assume at least you're unable to fly with a stick in the middle?
  9. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    All the cables are on sliders, so they can still move a small amount. Eg. the surge cables can still move in sway even when they are tightened. Same with the sway cables.
    G-Vest2.jpg
    Works well in my setup, don't know how well it would work with a proper F1 seat.



    Bladders are not as simple to get right as you may think for many applications. I have some handmade pneumatic rams that I would like to try, but fitting them will require some hardware/software changes to my current ballscrew actuators. Unfortunately cannot find the time at the moment and like I said - the vest is working well.
    Just posting my experiences, which I guess are very subjective. Don't claim to have all the answers and there is nothing like self discovery.
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    Last edited: Feb 10, 2019
  10. SeatTime

    SeatTime Well-Known Member SimTools 2.0 Beta Tester

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    My Motion Simulator:
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    Due to the front support arm, there is actually still space to fit and operate a flight stick in the middle, but I have it on the right hand side for lots of other reasons.
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    Last edited: Feb 10, 2019