Burnout physics/Exploits

Discussion in 'General Discussion' started by Nieubermesch, Jul 16, 2021.

  1. Nieubermesch

    Nieubermesch Registered

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    Good to see more people discussing on the thread, as I thought it would not get of the ground and I think it's quite an interesting and relevant behavior.

    Quite enjoyed reading your posts @green serpent and good job on giving more structure to the experiments. Other peoples posts are just what I expected from them - diverging and focusing more on other mentioned topics wich aren't really the real issue, for whatever reason. I would actually like to see them actually give their opinion about it, but the silence kinda speaks for itself and I am sure they also find this behavior odd.

    I saw a hotlap of the BMW M2 CS by Henri Sinik and it came to mind this especific thing. He was drifting the car around to get top world record times at indianapolis. If this is linked with longitudional push of the car during drifting that isn't quite present in reality like in RF2, then it explains why such a drifty way of driving is faster then normal driving... It's a very plausible and logical conclusion to arrive at.



    @mantasisg Good thinking, but yeah, sounds a bit like an excuse? I mean, if that was the case the car at the start of the burnout would be pushed forward either way, changing the place of the contact of the tires with the ground, never really ever getting to make holes in the tarmac. Just thought that from the top of my head, but it sounds too much like grasping at straws to me. Also, I don't think temperatures being dynamic on track will really make people feel like it's too complex. Even F1 games from Codemasters has that covered... Think about that!! Just think about that!! Time to bring that to RF2 once and for all S397.
     
  2. Comante

    Comante Registered

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    You're right, I'm a fanboy.. of scientific method, and I see none on those posts.
     
  3. mantasisg

    mantasisg Registered

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    @Nieubermesch Oh yes that is definitely an excuse. But it is also definitely how it is IRL, and it could be part of an equation. Surfaces has nuances too, not only tires.

    The starts of the burnout are still happening at low speed, so tire is still able to make lots of revolutions on almost same place of the tarmac, accumulating more heat in there, that it would happen if car would travel a bit faster.

    It would be interesting to find RL "brakey" examples that would be initiated at higher speeds, and see if car eventually halts to a stop with rear tires spinning with full power, or would it push locked front.

    And digging holes is just extreme side of an effect, it would really take a moment for tarmac to reach melting point, and it would have less friction already. It would happen at its very surface and that is enough to have contact friction affected.

    I wonder if you can do this test successfully in other simulations.

    I am also not talking about track surfaces being dynamic simply. But them being so at each and every place, like registering and calculating temp gain within every contact with a tire, maybe even registering and calculating effect of being in sunlight or shadow, which would probably be something not to happen in simulations for ten more years if not more. Imagine wet tracks evaporating only where it is sunny, and remaining wet where it is in shadow, but that is another topic.
     
    Last edited: Jul 17, 2021
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  4. Nieubermesch

    Nieubermesch Registered

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    Yeah, I see a lot of the scientific method in your posts too, right? You know some things don't require much more then just close observation to rule out right? Not all science has to be crazy complex and extensive to at least be close to some precision and validity... You're posts are just demoralizing and this is just an interesting thread to discuss this. If it would be the opposite and would be a guy singing praise about a certain behavior you wouldn't be commenting and he could be just as much not being scientific about it. But whatever man. It has been seen that the actual people giving critics - wrong or right - are pushing the sim forward with S397 being very good at delivering updates and on a good path. This is not to bash RF2, just another detail on physics that might be or not be right and contributing to handling characteristics of cars.
     
    Last edited: Jul 17, 2021
  5. Nieubermesch

    Nieubermesch Registered

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    Oh, I see what you meant now, not about the dynamic temperature of the track, but a realroad for track temperatures on specific spots and all. I guess the rubbered in line would be hotter then? It gets really microscopic at that point, the dynamics of the track progression and I also would think it would be too much work for something that I imagine isn't really that impactful at all, since I am sure thermodynamic balance with the air and everything will leave it somewhat all homogeneous- I guess ahah. About wet tracks would be cool though, and also the same for dry tarmac under the shadows. Guess that will come some day to sims. More realism wouldn't hurt anyone - not quite true :D:D.

    Well, I guess the car would have to be suspended at the rear and than lowered to make contact at the ground to see if the car would be pushed forward, but I would bet it wouldn't move with propperly locked brakes, but that's just me.
     
  6. Nieubermesch

    Nieubermesch Registered

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    I just did some test with rear tires in the grass while the fronts are on tarmac and there it stays fixed, so it's definetly something about the grip difference between both front and rear.

    I saw some videos of Assetto Corsa and the same happened in the limited cars I saw - fronts don't lock the car in place.

    Another sim where the cars actually remained in place was BeamNG. That sim definetly doesn't mess around with the loss of grip from my experiences with it.
     
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  7. Sim_Player

    Sim_Player Registered

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    Could it be just a graphical bug/ glitch ?
    The front tyres are probably moving under the physic engine but visually they seem static, this is my theory.
    I still haven't checked it yet (I forgot lol).
    Will try to do motec on this.
     
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  8. Nieubermesch

    Nieubermesch Registered

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    Hum, might be something to consider, but I wouldn't think the graphics would translate that wrongly, but a possibility. It sounds strange to me though, as it would mean you couldn't really lock the brakes of the cars in question even under 100% brake applied.
     
  9. Sim_Player

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    Took a while to get what you are saying ( not your fault), yea this would mean that even when you see visually brake locking BUT it isn't locking actually.
    It was just a guess anyway.
     
  10. Nieubermesch

    Nieubermesch Registered

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    Yeah, it would mean those cars under test can't lock the brakes, I think. If that was the case they wouldn't also lock during normal driving, as it would be harder to lock then.
     
  11. Nieubermesch

    Nieubermesch Registered

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    This is BeamNG with just two randomly selected cars. Keep in mind that BeamNG doesnt simulate tire temperatures and the car still manages to stay in place - although with some big back and forth motion with the suspensions and would probably disappear with actual grip loss at high temperatures.
     
  12. Lazza

    Lazza Registered

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    There's another side to this test possibly being overlooked: static grip.

    You're (as a group) comparing the rear spinning grip to the front static grip. It could be the front static grip at fault to some extent. Any ideas on verifying static grip? We know from past experiments and dev clarification that road surface angles approaching vertical don't work properly which rules out a steep hanging test.

    If Einstein is explaining general relativity and mentions the sky is green, that's wrong regardless of the rest of the paper. You CAN discuss specific topics without needing to give an opinion on the whole, and assuming no comment means agreeance is a logic error as well.
     
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  13. Nieubermesch

    Nieubermesch Registered

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    Of course it is, but the silence in this case actually speaks volumes when I see main focus of intervention on other side topics when the real one is thrown aside and ignored when I'd like that people like you actually gave this more importance then correcting someone about differentials, nothing more.

    It could be also static grip, sure. One is either higher or lower, from first supposition when looking at this tests, at least to me. Coupled with the link (weak and conjecture of course) about some possible excessive rotation and forward push on throtle during slides, I wouldn't say it is the front static grip - if the link is there.
     
  14. Lazza

    Lazza Registered

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    Off-topic but perhaps of interest to you: ISI made noises about doing this (to some degree) in rF2. As you can already tell, it never happened. I'm sure if it had it would also affect the track wetness. Maybe we would have had standing water in that case too. What we don't know is whether their planned implementation (being ISI and taking everything to the next level, like the tyres) simply wasn't feasible due to calculation and bandwidth requirements, or they ran out of time to get the level of attainable implementation locked in and executed.

    As in many areas I think you could have something quite coarse and imprecise, but good enough to convey a sense of reality. Anyway, sorry to extend the OT.
     
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  15. green serpent

    green serpent Registered

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    If every post about physics had to live up to those standards, there wouldn't be many more posts left of this forum about physics, that's for sure!

    Even the videos done by Niels, which are insanely in depth using data etc, fall short of the actual scientific method. I think we're all well aware here that none of this is actual science.

    Scientific theorys start out as simply ideas, just a hypothesis. THEN the scientific method is used to determine it's merit, and even after that it is still considered an approximation.

    Talking about ideas and possible explanations, I don't think there's anything wrong with that provided you don't say it's fact. I'll leave it to people smarter than me to do the actual science if they wanted to put that much effort in
     
  16. green serpent

    green serpent Registered

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    I have preliminary confirmation that the Mazda MX5 Mk1 mod can achieve line-locker burnout status at 10% rear wear with 90s street tire, and 50% rear wear with semi slick (turbo version). Awaiting experimental replication and peer review :p. No changes in setup. I tried making extreme changes in setup to camber and pressure and tried with no rear wear, but it didn't work. Only slight rear tire wear did the trick. Sorry for spamming this thread with low quality phone recorded vids. It's just easier as I can stay in sim and uplaod at the same time!


    As others have stated, I think it is very possible that track surface and the interplay between the track and the tire could be part or all of the issue, rather than the tire.

    As mantasisg stated, IRL the road surface would lose grip as the rear tires spin up. Perhaps what is happening is a) the track surface is not heating up as it would in real life and losing grip (as this is missing from the simulation I believe), and b) maybe it could actually be gaining grip as the track under the rear tires rapidly get saturated with real road, whereas the front tires remain on a non-rubbered in part of the track.

    I think I might try this on a saturated track, so at least the real road variable can be removed. See.. removing variables is scientific, maybe this IS hardcore science after all ;)

    P.s this is an awesome driving mod @mantasisg , I absolutely love it!

    Edit: fully rubbered in track did not really change things too much. Still front end pushes if rear tires have not been worn.
     
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  17. Korva7

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    Static real road didn't seem to remove the problem either.
    Asphalt melting not being simulated sounds like a possible reason.
    What about the molten rubber from the tire? It getting between the tyre and road would also reduce grip in this kind of slow speed situation, i think.
     
  18. Sim_Player

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    Did some standing burnouts on BMW M4 class 1 (since it is supposed to be latest greatest)
    m4.PNG

    Looking at Graph , as you can see wheel rotation on front is 0 (revolution per second is the unit) for entire time of doing burnout.
    Also speed itself is NOT zero and so is Longitudinal G is also NOT zero as well (very low both of the readings but still ).
    Looking at suspension tho it looks like car is oscillating little bit...so my theory is that this small oscillation/vibrations are causing car to hop a little bit ,hence car is not staying at same spot....it is not rolling (probably) but mini hopping/jump whatever you like to call it.

    Edit : On maximum tyre wear (when HUD shows "0") the car became little bit more stationary.

    Edit 2: I got pointed out (by lazza) that engine RPM cutoff might be causing oscillations
    so better picture ->
    3.PNG
     
    Last edited: Jul 18, 2021
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  19. mantasisg

    mantasisg Registered

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    Speaking of static friction, it definitely is at play. Although I have not succeeded in several cars I have tried this test, but front engined cars seemed to do best, mid engine worse, and rear engine cars worst. Which of course happened because weight distribution, thus static friction at front went lower as engine weight moved more towards rear.

    Oh thats cool. Thanks. I have tried Miata, and it didn't work for me. Although it was standard engine and with fresh tires. Turbo version with worn tires certainly seems like better candidate to success in this test. Though 90s tire not very grippy to begin with, and semislick with 50% of wear - massive wear. But it is nice to see it working at least like that.

    I also thought perhaps people IRL wouldn't really do this thing with new fresh tires. But I guess it is irrelevant, because by doing this, tires would get very used in several seconds.

    Good insights about surface getting rubbered, and thus even increasing friction at that place of a spin up. Tires have parameters for various things for rubbered groove, which some of them are for sliding.

    I don't want to butcher tires just so this test would work, but I'd love to try to modify them to get better results at this, and not to make the car handling any worse, who knows perhaps it would be possible to achieve more realistic tire configuration by following this test. Will try it some day. I'd probably try altering some of those: altering wear at highest temps, altering highest temps friction loss, altering rubbered surface effects for sliding, altering high velocity sliding effect for sliding friction (I assume it counts velocity of actual tire rubber vs surface, not car velocity), it would probably be helpful to learn about WLF stuff for once since it is in play. I never played with gasses parameters, but perhaps getting more of pressure increase due to tire heating would help, as well as heat transfer to road surface parameter.... Well it sounds like this thing could potentially lead into remaking the tire lol But it wouldn't be acceptable to get worse results from the tires, just for getting better results in this test, which also would be a sign of something not working the correct way, as ideally everything should become more realistic.

    This is interesting idea, it must have a play I guess. Although iiric I have read that tires can wear differently, some can kind of melt-off the surface, and some tend to wear into kind of rubber dust or something like that. Anyway, I also remember reading that black marks that we can see on tarmac from tires, happens due to bonding of heated tarmac and heated tire touching, although I guess it also could be just pieces of rubber getting stuck in irregularities of the tarmac.
     
  20. mantasisg

    mantasisg Registered

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    This is iRacing clip I found, I was almost sure it would work in iR since it is known to have very sharp high peak tires, while at the same time being pretty bad to slide, and also very hard to recover from overheating tires, so I don't think it marks iR as overall correct, but certainly for this test it works:

     
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