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Question Which way should my rig roll going round the Daytona banking?

Discussion in 'Assetto Corsa' started by Andy Booth, Jul 23, 2018.

  1. Andy Booth

    Andy Booth Active Member

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    My Motion Simulator:
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    I thought I had my DofReality P3 Rig all working as it should until I started running my DRM Revival BMW M1 round Daytona (Street Circuit) using Assetto Corsa.

    Up until recently I thought the motion cues created by the rig were all as they should be with pitch and roll as I expected them to be until.....

    As I rolled into the banked left hand turn 1 my motion rig rolled to the right and it just didn't feel the way it should.

    I know I can just switch the direction of the motion but I started thinking "What is this motion rig trying to simulate and what should I be feeling?

    Daytona is a 31 deg bank angle. Going round the bank I do have to turn but what would I be feeling in a real car? Would I feel the centripetal forces meaning I would be pushed sideways in my seat to the right or would I be feeling vertical downward forces because I'm at 31 degrees and gravity should make me actually slide in my seat to the left.

    With the way my motion rig was set, and felt fine up to this point, when I did enter the banking my rig rolled to the right, simulating the centripetal forces I suspect. But it just felt all horribly wrong.

    With the rigs roll dof set the other way, driving around the banking felt more natural with me feeling the force of gravity pushing down, which because of the 31 deg bank felt like i was being pushed slightly to the left.

    I suspect speed has something to do with it. If the car is motionless on the bank then gravity will result in a force due to gravity pushing the driver into the lhs of the seat. At a certain speed, the force due to gravity will; be equal to centripetal force so the driver will feel no putt to the left or the right. If speed increases further then centripetal force will exceed gravity and the driver will be pushed to the rhs of the seat.

    I think I'm correct.

    So, does the motion software simulated by our SimTools take speeds and banks into account? I would expect it to, however, my DofReality P3 rig just seemed to roll to the right and stay at that pitch until I drove off the bank and onto the flat, the motion rig just leveled out.

    I may be wrong but the rig just feels like the pitch is driven by the angle of the road surface only and not by centripetal forces expected by the speed.
    I'm not sure if the sway is set wrong or something like that, but the rig just didn't feel right. Does Simtools simulate centripetal forces?


    Sorry if my explanation leaves a little to be desired and I didn't do much testing other than switching the direction of the roll settings.
    I had never noticed this wrong feeling of roll being wrong before but I don't think I had run a highly banked track with the motion on (when I'm racing I usually turn motion off because I find Im usually a lot slower).

    Your thoughts gentlemen
  2. sam poole

    sam poole Active Member

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    3DOF, DC motor, Arduino, Motion platform, 4DOF, 6DOF
    I found problems like this and still do its a time consuming process I think the blend is really important to this so I have a higher percentage of surge and sway over roll and pitch which is not good for flying also different cars behave very differently found best to make small changes at a time
  3. Andy Booth

    Andy Booth Active Member

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    Yeah, but which way should the rig be leaning when entering the banking at Daytona?

    I appreciate what you are saying about surge and sway (although I don't think surge comes into this discussion), but what I cant understand is if the rig is supposed to simulate the car or the forces on the driver.

    I think the rig 'is supposed to' try and make me feel like centripetal forces are causing me to be pushed in the opposite direction to the turning moment which was how the rig was set up and seemed to feel right however the banking at Daytona just felt awful which prompted the initial question.

    Andy
  4. Agosky

    Agosky New Member SimAxe Beta Tester Gold Contributor

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    You are right, it depends on vehicle speed and also radius of the turn.
    Stability between gravity pulling sideways and centrifugal force occurs when: tan 31deg = v^2 / gr -> v^2 = tan 31deg * gr.
    Assuming turn radius of 500m (just a wild quess) gives v^2 = tan 31deg * 9.81m/s2 * 500m = 2947m2/s2 -> v = 54m/s = 195km/h = 121mph.
    Below that speed centripetal force pulls you to left, and above that centrifugal force pulls you to right.

    Lateral G-force value in game is transferred to rig roll axis, and it does not take in account situations when there is opposite force created from vehicle tilt.
    I think there is no good solution for this problem. Rolling rig either left or right depending on speed would make things only worse IMO.