1.04 update - Physics changes - Your impressions?

Discussion in 'Gran Turismo 6' started by SillyBillyP, Jan 28, 2014.

  1. TenEightyOne

    TenEightyOne

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    All good, that isn't what I was responding to. The part I quoted said "the tyres might be able to accelerate the car up to 2G, while in a heavy car the same tyres might only be able to accelerate it up to 1G.".

    As I pointed out; I believe you're referring to the lateral resistance of the tyre against mu, the tyre itself has no accelerative properties thus you were incorrect.
     
  2. eran0004

    eran0004

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    Acceleration is a change in velocity. When you turn the car, you change the velocity of the car. Velocity is the rate of change of position of an object and consists of speed and direction. When you turn the car, you change the direction - so it's an acceleration, even is the speed is the same.

    And the tyres do have accelerative properties. The force from the friction between the tyres and the road is what's accelerating the car when you change direction. The more grip > the more friction > the more force > the higher acceleration. If a certain tyre works with the force of N on a body with the mass of 500 units, acceleration will be higher than if the same tyre with the same force works on a body with the mass of 1000 units, given by the formula:

    Acceleration = Net force / mass.
     
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  3. TenEightyOne

    TenEightyOne

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    You may change the direction but you do not necessarily change speed or velocity. You in fact provide a de-acceleration in normal conditions. I see what you're saying but you're going about it a bit arse-backwards.
     
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  4. eran0004

    eran0004

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    Change in direction is change in velocity, because velocity is speed and direction. Change either of those, and you have an acceleration. Decceleration is also acceleration, only negative.
     
  5. TenEightyOne

    TenEightyOne

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    And going up is going down, only negative. There are differing words because they mean differing things.

    In your examples you're examining body roll versus the lateral cumulative mu and illustrating that on a single plane. The velocity of the overall body in the top down plane (or in three dimensions) is irrelevant to your illustrated plane. The acceleration or de-accellaration therefore doesn't exist.

    You also fail to note tyre profiles, grip is affected by the pressure of the tyre's surface area on the road surface. Dependent upon the shape of the tyre a car can lean onto the "edge" which suddenly delivers an enormous amount of grip via a narrow footprint. That's normally a point at which the lateral momentum curves suddenly lunges across the slip curve and a ground-vehicle inversion occurs.
     
  6. f1webberfan

    f1webberfan

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    Then my question is to what extent? Because power sliding is not always the fastest way. And even if I do agree that GT6 is miles away from some other rally simulators ... actually I'm OK with the idea that in rally full power is not always best. Just look at Loeb and Ogier.
     
  7. Muxlee

    Muxlee

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    Speed and Velocity are not the same thing. In physics they are defined like this one is a vector Velocity, the other is speed is Scalar.
     
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  8. TenEightyOne

    TenEightyOne

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    Precisely. @eran0004 was discussing the momentum of the body over the unsprung mass but confusing things by trying to make scalar acceleration a sub-function of the vector instance.
     
  9. xSNAKEx

    xSNAKEx

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    Velocity is just speed regardless of direction. It has nothing to do with direction.
     
  10. OdeFinn

    OdeFinn

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    Power sliding is fast way if skidding is around 1-15% "overspeed" on tires, if pushing pedal to medal and tires are rolling more than 15% over your actual speed you are losing time.
     
    Last edited: Feb 22, 2014
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  11. dylansan

    dylansan Premium

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    In physics it definitely includes direction.
     
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  12. xSNAKEx

    xSNAKEx

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    Yes actually you are right in the context it is being discussed. I was thinking of "speed". Doh.
     
  13. subsist

    subsist

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    Velocity needs direction, without direction you have no velocity.

    I.E Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is called "speed", a quantity that is measured in metres per second (m/s or m·s−1) in the SI (metric) system. For example, "5 metres per second" is a scalar (not a vector), whereas "5 metres per second east" is a vector.
     
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  14. NinjaDesignz

    NinjaDesignz

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    Great Physics lesson! :tup:
     
  15. LazyJK

    LazyJK

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    On hard surfaces, not on loose ones.
     
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  16. OdeFinn

    OdeFinn

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    Even less skidding is helpful on loose surfaces.
     
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  17. jr93alty

    jr93alty

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    A lot of you are discussing physics terms and it's cute but doesn't matter. The point of sliding on loose surfaces is simple. Basically, you can convert sideways motion into forward motion easier than it is to accelerate a heavy car on a loose surface. It's all about exit speed, not traction. You can break it down into vectors if you want but it's simpler than that. Accelerating from a slow speed on soft dirt is very hard. Anyone that drives in bad snow knows that maintaining speed, regardless of direction, is always better than coming to a stop. This is why some cars have adjustable traction control depending on the surface. It's also the same reason that high jumpers have fast approaches. They convert energy in one direction into energy in a completely different direction.
     
  18. OdeFinn

    OdeFinn

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    @jr93alty, on loose surface too much skidding during that "change of direction" and you'll end up going straight out from corner.
     
  19. eran0004

    eran0004

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    In racing there's a difference between acceleration and decceleration. In physics they're the same.

    In racing, acceleration is gaining speed (forward, usually) and decceleration is losing speed (braking, usually). In physics, acceleration is any change in velocity (direction and "speed") in any direction. When you hit a jump with the car, it's being accelerated upwards. When the downforce of the X2014 pushes the car down, it's accelerated downwards. When you turn, it's being accelerated in a new direction.

    One can think of acceleration as being the forces you feel when you drive the car. Accelerating, braking, turning, jumping, in physics those are all accelerations. Even crashing is an acceleration, and often a very violent one. If someone punches you in the face, that's also an acceleration. Earth is accelerating all the time as the gravity of the sun makes it rotate in an orbit.

    Well, the details of the tyres aren't really important in this model, as it's meant to illustrate the point about center of mass. Usually when a car is leaning at a great enough angle, the remaining grip combined with an elevated center of mass is enough to make it roll if you turn in the wrong direction so I'm just assuming that whatever the grip value is, it's enough to do the job that's required.

    Tyre details are important if you're building a physics model, though, and I wonder if the GT6 physics takes the angle between the tyre and the road in consideration when it calculates grip?
     
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  20. LazyJK

    LazyJK

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    I cannot agree with that. As I mentioned previously, grip on loose surfaces comes from a completely different physical phenomenon than on hard surfaces.
    The grip on hard surfaces comes from particles of rubber interlocking with particles of pavement/asphalt. It cannot work on gravel or snow since the particles of gravel/snow are loose: there is nothing to generate grip, save for digging into the surface.
     
  21. FussyFez

    FussyFez

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    Great Video but I must point out that this is an open diff, and not an LSD.
     
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  22. OdeFinn

    OdeFinn

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    @LazyJK, yes and no :) depends much how ruff tires are, suspension etc, so partly true when circumstances are right.

    @FussyFez, I know, but when you know how normal differential is working its easy to understand how limited slip differential is working.
    Everyone who don't know basics of differential would just get confused if there was picture of opened lsd, or explanation.
     
  23. Muxlee

    Muxlee

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    Thanks for this - I really did nt want to come back and explain it to 1081 who completely misunderstood it
     
  24. FussyFez

    FussyFez

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    Agreed. I had presumed you knew, I just wanted to make it clearer to anyone else.
     
  25. LazyJK

    LazyJK

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    My information is based on a series of tire articles in a Polish rally magazine but also other sources, like "Going faster!" and "Speed Secrets" books and a couple of things I read online. Can you tell me where I can find info on other principles of grip on loose surfaces? I'm an amateur racer in real life and I would be grateful for such information.
     
  26. OdeFinn

    OdeFinn

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    @LazyJK, Long story to tell, next quote will open something of it, I can add more later if that is not opening it enough.
    Something, ideas.. :)


    Top Gear hints to become "average racer" ;)
     
    Last edited: Feb 24, 2014
  27. BHRxRacer

    BHRxRacer (Banned)

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    Ugh. Old story here but, I think MR cars are a little more harder to drive. Maybe it's down to the tyres being colder or something.

    I never complained about the physics before in any version, I just adapted. However it's frustrating to jump back in the game after a while to find the physics changed EVERY time.
     
  28. Flaren89

    Flaren89

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    Soooo... Now talking about 1.05... Still not out there?
     
  29. Martin_320nm

    Martin_320nm

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  30. gambleboyen

    gambleboyen

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    Driving off road in Willow spring used to be a blast. Now it's boring as ****. WHY!?!
     
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