Tires inner and outer temperature

Discussion in 'General Discussion' started by Pablo11, Aug 8, 2015.

  1. David Wright

    David Wright Registered

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    An under- inflated tyre will run hotter but not at a higher pressure or it would then be over-inflated. The heat generated by under-inflation has only a modest effect on pressure. Pressure is proportional to absolute temperature so if a tyre is 20 degrees hotter due to under- inflation the pressure only goes up by 6% .
     
  2. David O'Reilly

    David O'Reilly Registered

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    The test was run with the ISI Nissan GTR (with the Nords 24 BOP changes so nothing to tyres).

    I also forgot to mention that on long straights the inner edge stayed hot (sometimes slightly hotter) and in the corners the middle and outer temps increased.
    This makes perfect sense as of course the car will be running on the inside edge on a straight but when cornering the lean/and G/and distortion will cause the middle and outer sections to do more work.
    So in fact the temperature delta is lower mid corner as temps of these other parts of the tyre rise nearer to the inner edge temp.
     
  3. Lgel

    Lgel Registered

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    I am nitpicking, you seem to contradict yourself there between your first and your second statement, a hotter tire will run at higher pressure if volume remains constant. Law of perfect gas P*V/T = Constant (T is absolute temp, 273 + temp in K).

    In F1 this has caused many accidents due to the contrary effect (slow down after pace car, slower temps, less pressure, lower ride height, diffuser stall).
    On a touring tire, under inflated tires can bring tire destruction at high sustained speed.

    Cheers.
     
  4. Gonzo

    Gonzo Member

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    Guys, there is no new or old tyre-modell.
    If we re talking about the "old" we usually mean the rF1 tyre-modell.

    In rF2 the new tyre-modell just gets updated. And one of the new features is the new CPM (contact-patch-modell) which adds additional calculations / additional realism.
    You can already drive this with the Corvette and the Indycars. Easyly noticeable with enabled tgm-display (check your PLAYER.JSON). The patch is way smaller compared to tyres not using the newest tech.
     
  5. TJones

    TJones Registered

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    @ Lgel No, i think what he wrote was correct. The heat generated by an underinflated tyre, because of more chassy flexing, doesn't increase the gas pressure that much, as you think.
    You may get damage to the tyre, because of to high flexing/stressing itself, not the increased pressure.
     
  6. Max Angelo

    Max Angelo Registered

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    It is not matter of the parameters number, and in informatic adding complexity without a goal to accomplish is pointless. :)

    Oversimplifying, with a metaphore i think we can say that rF1 has a "ptolemaic approach" and rF2 has a "copernican approach", where the Earth is is the slip angle and the Sun is the tire: a revolution, actually.

    This revolution is possible because the power of the current CPU (compared to 10 years ago) and because the loockup tables ... a little bird told me that without such tables the computational power would multiply about 1.000.000 times!

    Clear, tastes are personal and not questionable, but the tires in rF2 are elastic bodies, observing the physics rules of elasticity ... in rF1 the tire was "solid" (with "fake" elasticity).

    All in all, everything is improvable, also the TGM obviously, but, from the "simulation perspective", the step ahead in rF2 is HUGE.
     
  7. David O'Reilly

    David O'Reilly Registered

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    I love you guys.:eek:
    You had me at contact patch.
     
  8. Lazza

    Lazza Registered

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    You said you were worried that the tyre model would end up "not being universal (same for all cars with different parameters), but different for every car".

    The tyre model takes the physical properties of the tyre (shape, composition) and works out how it will behave at any particular moment in the game. A more complex model will do a better job of turning those physical properties into realistic behaviour, and will do so regardless of varying tyre types (than a less complex model would). The number of parameters is another matter, but take a look at a .TGM file and see if you think 10 parameters would do the job :)
     
  9. Lgel

    Lgel Registered

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    @Lazza

    Let's say that I have been professionally involved in simulation development projects (not of cars).

    In many case our model didn't suit the phenomenon we tried to simulate.

    Very often the team would come with the idea that we had not taken enough parameters and relations between variables; with each step the complexity of the model increased, and alas our model was further away from what we were looking to simulate.

    When the model got so complicated that no one could master it, it was time to stop and think.

    Very often the solution came from a thorough revision of each variable we had taken into account, whether it was really significant, and ended in a simpler (not trivial either) model that the one we had in our hands before.

    A model we could our selves understand, whose limitations were known, which could run on the computers available at the moment, and that we could explain to the customer.

    I trust ISI engineers to know what they are doing, I was just commenting the fact that a more complex model doesn't always mean better model.

    Cheers Lazza.
     
  10. Gonzo

    Gonzo Member

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    I guess the current model is already VERY complex.
    Its not just a step from rf1. Its a revolution.

    Everybody can feel and see this. Deformable tyres, flatspots, vibrations, way better ffb, etc.
     
  11. Euskotracks

    Euskotracks Registered

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    In my opinion the tire model is very good in terms of general load vs deflection and grip behaviour. However, what seems to be failing is the accurate calculation of the contact patch area under different conditions and how the heat is generated within that contact patch. A bad theoretical model can lead to inaccurate tire thermal simulation. Heat is generated at the contact patch by frictio where sliding and load is greatest and of course some conduction also takes places with the road even where no sliding takes place.

    Enviado desde mi GT-I9505 mediante Tapatalk
     
  12. Max Angelo

    Max Angelo Registered

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    Physics of elastic bodies and thermodynamics are not simple branchs, but when the goal is not "to simulate how a tire behaves under different loads" (Paceyka like model as in rF1, where the tire was calculated by its slip angles, aka "ptolemaic approach"), but the goal is to simulate an actual tire (physical/thermodynamic model as in rF2, where the slip angles are just the natural consequence of the physical model and the compound, aka "copernican approach", as in the gross metaphore of my previous post) you have to take in account the added complexity in the programming (i think TGM was the hardest job in the professional life of mr. Groening, ie the genious who has in charge the physical engine since SCGT) and the added complexity for the modders.

    But, the old tire model had a development lasting about 15 years in its reincarnations (starting from SCGT and ending in rF1), so we can expect huge improvements, in the years, in the TGM too.

    For instance still, after thousand hours spent in the TGM, the work is not completed ... i think is planned an improvement of the CPM, so users can expect in future a better

    Creating a good tgm tire is not easy for sure, but modders can use "tires made in ISI", can try to learn or, if the modding project is serious, can ask for help to mr. Borda (who will send me a damn if he reads ehehe, seen he is pretty busy).

    In the years, we can also expect a wider "library" of tires and spreadsheets, so to facilitate the modders.

    For sure, to the rethorical question -might we step back to the previous millenium with the tire physics?- the choral answer by ISI would be -NEVER!- :)


    Back to the OP topic

    1) tire pressure has to be taken in account only in the cars having the CMP enabled

    2) tire heat is the superficial one, with repentine changes under load ... watching videos with thermal cam or with superficial temp measurement, the tire behaviour in rF2 is "fully compatible" with real life tires, but improvements are still required and planned.
     
    Last edited by a moderator: Aug 11, 2015
  13. Gonzo

    Gonzo Member

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    1) is not entirely true. Tire pressure has become more realistic and more important compared to tires without cpm.

    And oh yeah, Mr. Borda is going to kill you for sure :D
     
  14. Max Angelo

    Max Angelo Registered

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    Hehe, talking of semantic, for not native english users as us is risky LOL, but why take in account tires without CPM, seen that they are outdated? :)
     

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