How does tankslappers work ? And aren't you too good at avoiding them ?

Discussion in 'General Discussion' started by mantasisg, Aug 26, 2019.

  1. mantasisg

    mantasisg Registered

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    I didn't find it to fit in my other threads, also in my opinion issue is so important it has to have its own. So here is my usual "it is time to pay attention to physics type of thread", where I think I have an iteresting topic to talk about, and where we will probably end up with posts like "sim x is better than sim y"... Just joking. Well I hope not gonna happen here.

    I wonder but sure have no idea how are you dealing with tankslappers ? Are you doing great ? Personally I am doing really well, it is really rare thing for me, and not really only talking about rF2, but pretty much every sim. Recently there were two events where tank slappers were touched with a shade of disbelief, like if they should'nt happen. First, Renato Simioni mentioning ISI tires (not S397) as being too sharp here https://www.racedepartment.com/threads/automobilista-2-new-preview-video-released.171836/page-10, and I think that is at some level debatable. Then Austin Ogonoski made a video sharing doubts about iRacing tires sharpness with also including an examples of tankslappers, and with example from iR saying that it should not have happened there...

    I thought that in my personal experience tankslappers already almost never happens, not even at light degree, and people still thinks that there is something wrong (unreal) about it.

    But perhaps I don't understand something. I am interested to discuss with you guys why tankslapper happens in the first place ????? and we do know that IRL it does happen often, and often leads to terrible accidents or very scary moments. How do you think, what causes it IRL, why car just doesn't continue straight forward when it grips up during oversteer ?

    Here is small example of lucky escape, but very chaotic indeed:

    1:35 in the video, what is wrong there, poor FFB ? Input lag ? Wrong tire model ? Driver sleeping ? It just never happens for me...
     
  2. Emery

    Emery Registered

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    Tank slappers are due to driver over-corrections as a reaction to wanting to keep the car on track. They often come off the gas too abruptly in addition to too large of steering inputs, which compounds the problem. They particularly compound the problem if they've got 1/2 tank of fuel sloshing around!

    Drivers who accept they've made a mistake will usually allow themselves the opportunity to gracefully go somewhere they didn't intend to and thus avoid the tankslapper. They pay a different price by compromising the driving line, but gain from not losing control of the vehicle.
     
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  3. Korva7

    Korva7 Registered

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    With low ffb, slow steering, a bit too much damping effect and maybe car with low caster and it starts to feel like these kind of mistakes are possible. So maybe that car has too light/over powered and slow steering.
     
  4. vittorio

    vittorio Registered

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    Last edited: Aug 26, 2019
  5. Lazza

    Lazza Registered

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    I had a tankslapper 2 days ago (in rF2 :D) while practicing in historic F3. Combination of not really paying attention to when I needed to straighten up my steering and keeping too much power on. Then once it went I still wasn't really trying hard to save it AND I backed right off, which transferred weight to the front and kept it going.

    I've hardly had any in my recent time in those cars (months) because I've been focused on controlling the car while chasing lap times, or I've been in a race where some sort of race-mode kicks in and I put survival above some extra tenths (so if I end up on grass I back right off, if I start sliding I aim to control it before pushing again - during practice I take more liberties). But central to all that is a few months ago I finally learned to feel that pendulum moment where you need to stop counter-steering or you flick the car round.
     
  6. mantasisg

    mantasisg Registered

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    Interesting ideas on subject. I think that it is all about rear tires gripping up very quickly during oversteer for some reason. I think if you are oversteering and not spinning out, then it means that you already have grip at the front. So following that logic it only makes sense that tankslapper is a sudden grip increase of the rear end. And then there is super tight time gap to countersteer.

    But everything what has been said makes sense because adds up. Lift off throttle can result in quick grip increase, because tire slip ratio will decrease quickly and tire should come back to its traction eclypse. But on the other hand abrupt lift will cause weight transfer forward, and loosing grip because of decreasing rear enf load. Difficult case indeed. I don't think over correcting can cause more than spinning out, but I suppose if there is a lot of rotation to be done when it is time for countersteer, then it also can be hardly possible to physically set the steering in time before the tank slapper...Low FFB also must have to help to countersteer faster, as well as lower steering ratio...

    But I think first of all it is sharpness of grip at the rear end at the limit.

    @Lazza It is time for me to drive those F3 cars, sometimes I forget that they are there, but they are great choice to use in rF2.

    I am off to rF2 now will drive some F3 and will attempt to get some tankslappers on purpose.
     
    Last edited: Aug 26, 2019
  7. mantasisg

    mantasisg Registered

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    So back now, one of the best evenings with rF2 for me so far, or should I say nights. A lot to say.

    First of allyes some cars/tires really caused me some tankslappers.

    Only driven at Guapore same conditions, I love that track.

    EVE F3 - no chance to oversteer till stiffening rear and shortening gears. Nice solid, sharp feel of tires. Did have a tank slapper when did turn into slide too much on purpose.

    EVE F2 - sharper driving than F3, nice and solid feel of tires, definitely felt increased risk to get a tankslapper, but didn't try to get it on purpose, and it didn't really happen, but it is challenging car.

    EVE F3 - sharper feeling again, nice and solid feel of tires, though little bit of soapyness appears, but tire still feels solid nice and sharp. I did get a bit of tankslapper with this car when on the limit.

    Houston G6 - very soapy feel of tires, but if you manage to set the car it is possible to corner with quite good stability, but mostly feels like all wheel drifting constantly. That car didn't feel like it could ever slap.

    March 761 - incredible feel, very sharp and very solid connection with road through the tire, got a couple of race ending tank slappers when exiting T2 because wasn't countersteering quick enough, this car even had a little bit of flatspots feel, which I thought got removed from sim recently

    Mclaren M23 - Tires has completely no sharpness, quite possible to drift all around without much need to be very concentrated, very easy to correct, will never slap. But it takes its share if you want to do a very good laptime, thats how simracing cars feels to me to be trending since Assetto Corsa, a bit extra drift instead of a bit extra concentration.

    Will be checking Camaro GT3 against new GT3 cars next time.
     
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  8. Lazza

    Lazza Registered

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    Regarding the tankslapper itself, I'd summarise it in phases, easiest to hardest:
    1. Applying enough steering, and enough power, to make the back end of the car step out of line through a corner, but keeping the wheel straight and easing off the power recovers it.
    2. More power, into a proper drift, and then past. Car spins and stays (mostly) on the track. (ok, this might be easier than 1 lol)
    3. Into a drift, recognise the tail is going wide, countersteer (towards the outside of the corner) and ease off throttle. Angle of car relative to direction of travel increases less quickly, finally stabilises. And then spin off the outside of the corner (overcorrection) as the growing rear grip combines with the steering lock. Like a Scandinavian Flick, except you don't want it.
    4. As above, right to that point of stability, then react immediately when the car starts to flick in the other direction. The whole process repeats in the other direction, as by the time you catch up with the steering the car is already drifting the other way (but less than before). By the time you catch up with the steering enough to catch it, the drift is already stabilising and now you're steering hard into it. Now it flicks again, and you react again, etc. Tankslapper.
    5. You recognise the point of stability is being reached, and modulate steering and throttle to hold the drift, or/then straighten the steering in anticipation of the flick, which exits the drift.

    Real life drifting guides highlight that last one as being tricky to get right. There are many videos on youtube covering it.
     
  9. D.Painter

    D.Painter Registered

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    Basic cause off tank slapping is over correction. Once the wheels (tyres) grip up the car flicks the other way.
    I've always found to not turn the front wheels that much and let the slide acre as it may till it dose grip up. May back off slightly on the accelerator to stop wheel spin. When the tyres loose grip it's easy to loose the car from wheel spin so you need to back off a bit to reduce the possibility of that happening. Off cause just coming off the gas completely isn't a good thing to do either. Sometimes you win, sometimes you loose but I don't get tank slap.
    Can't compare sims. Only have rF2 and AC. Both work the same way IMO on this point. Off cause it's difference between mods, cars, tracks, as to how quick the grip picks up.
     
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  10. mantasisg

    mantasisg Registered

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    I am quite interested in the mechanics of oversteer, I think understanding tankslappers uncovers (or should rather say brings me closer to uncovering) understanding about it.

    I am pretty sure that tankslappers are all about being able to be in tune with rear end grip with the way you are countersteering. I'll try to show how I see some typical oversteer mechanics basics consisting of spin into the corner, and spin out of the corner (the tankslapper).

    Red and arrows and blue arrow - relative vectors in refference of CG
    Green line - path of rear end
    Yellow line - path of front end

    [​IMG]
    Oversteer spin out into the curve.
    Spin
    Rear slip always increasing till it is sliding out of control completely. Yaw moment causes rear to over rotate the front end. Front end starts to roll backwards in the refference of CG.
    Save
    Straightening front wheels or even turning into the spin direction slightly in such way that tire would appear in transverse position regarding to its direction of motion. Producing "braking force" this way, preventing wheels from rolling freely backwards in refference of CG, hopefully matching front and rear velocities and stopping the yaw moment. Can attempt to tap brakes to win some weigth transfer to front and regain grip there frist once car is sliding in equilibrium, might work with some cars. Like Verstappen spin save in Interlagos.

    Oversteer spin out out of the curve (tankslapper)
    Spin
    Suddenly or unexpectedly rear end regains grip for many possible reasons. Driver is unable to countersteer fast enough, or driver corrects the oversteer with steering when it is unnecessary to do it or/and steers into a slide much too much. Due to high speed and speed of rear grip regain driver is unable to countersteer precisely, or it is not even possible. Plus vehicle is carrying inertia pointed linearly the direction of linear velocity out of the turning radius which "helps" a vehicle to turn in sharply out if the front wheels are pointed at wrong direction the moment rears grip up.
    Save 1
    Attempting to sustain the slide for longer and control rears to grip up in smoother, slower way. Can be done if friction is low enough during that, or car has enough power to keep tires spinning. Sawing the wheel into the turn at short inputs to add little bit of slip angle while searching for equilibrium. Slamming on brakes to shift weight forward unloading the rears, but this one is difficult because slowing down will likely make rear tires to regain grip more suddenly, though you can lock front tires, and as we know tire can perform cornering well if it is dealing with a lot of braking force and tankslapping is a motion of a car making a sudden turn in braking should reduce that. In the past I have saved some cars from almost certain spin out from oversteer by slamming on brakes hard and guiding them back into stability this way, but this may not work for every car, for example if by doing this you'll lift rear wheels in the air, but this also could help to sustain the slide, not sure in which direction it would be then :D
    Save 2
    Really really really really fast countersteering action, almost like if you know how the steering should be before you get any clues from the car.
     
    Last edited: Aug 29, 2019
  11. mantasisg

    mantasisg Registered

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    @Lazza

    I am still confused about what is called to be countersteer. I call it the steering back after catching the slide because you are kinda countering self aligning of front wheels assuming that they are pointed not in the needed direction for a corner exit. Otherwise aligning from just rear end gripping up would be enough, because once rear grips it should just simply want to go where fronts are pointing at. But you saying that countersteering is the turning into a slide (out of the corner) also makes sense (because countering the direction of the turn), but the wheels really aren't doing that, it is just compensating for rear end changing cornering radius relatively to front...

    Feels like we think about these mechanics in similar way though. I just don't know if drifting is good area for this, because they don't use tires with narrow optimum slip angles windows, at least as much as I am aware about them, so naturally tankslappers just may be less of a problem for them. And if they still say that it is tricky to get right, then it means something. And yeah tankslappers definitely is like a scandinavian flick just unwanted, should be totally same mechanics just with different reasons. This also makes me think that it should be very easy to cause scandinavian flick, though I sometimes find it a bit difficult in some sims/cars.

    @D.Painter

    Yes it seems like over correction is indeed main reason, though I would say it is main ingredient. Over correction, or bad timing. True abbout acceleration, if you'll drop too much you get grip too soon, and if you use too much throttle you never gain grip that is needed. I think the main physics friend here is the slip angles and slip ratios... so... just very basic parameters. If they are wide you can easily let a bit of slide to happen and just chill, but if they are narrow, then you are kinda forced to correct slides just right because either spin into the turn or of the turn will happen if you go wrong few degrees in one or other side. Simracers hate that.
     
  12. Lazza

    Lazza Registered

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    A "tankslapper" isn't a single flick, it's a series of them.

    Your oversteer into the curve is my scenario 2.

    Your oversteer out of the curve is my scenario 3.

    2 is very easy to do. Too much power to maintain traction, be turning. That's it. 3 requires you to actually try and 'save' it in a basic way, by following the rear of the car with the front. You're literally turning away from the direction of spin, steering 'counter' to that spin - countersteering.

    With small angles you can do this saving with little regard for power. The angle is low enough, the lateral movement relative to the front of the car is small enough, that steering with the front wheels can follow the rear. Drift cars have extremely high steering lock which means they can follow at very high angles, but other cars will exceed that limit and simply spin if you overdo it.

    Maintaining or saving higher angles requires moderation on power, limiting the traction loss at the rear. That gives the front tyres time to get dragged across by the rear, avoiding a spin. I suspect it's the fact that both ends are sliding, that makes the balance edge feel sharp - when you feel the slide coming to a stop (the angle of the car is stabilising) it doesn't just start moving in the opposite direction - both the rear and front suddenly regain some grip, so now the rear of the car wants to move backwards (relative to travel) and the fronts are turned in an agreeable direction (counter to the direction of the original spin). The lazy driver in scenario 3 has gone from a 'save' to now setting their car up to flick out of the corner.

    What you want to do, is scenario 5 - ease out of the slide by preparing for that regrip, straightening the front wheels so they don't abruptly regain traction while pointing out to the side, but instead maintain a slide as they straighten to the new direction of travel. I don't think there's a term for this corrective steering at this phase.

    A tankslapper, scenario 4, is what happens when you get the timing wrong. You miss the opportunity to drag yourself out of the slide before the spin reverses, and that happens so quickly you can't catch up with it until the car is sliding in the other direction and the spin starts to slow again. Now it all repeats, because the subsequent slides are less controlled (and shorter in duration) than the first one was. The outcome isn't predetermined - you can flick yourself into a proper spin at any of these points, or you can reduce the severity of each one until you get back to the low angles mentioned earlier and you pull yourself out of it.
     
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  13. dylbie

    dylbie Registered

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    All you need is over-steer and over-correction... or an MR2!

    I've owned a 1988 MR2 for 12 years now and had a few tankslappers - mainly in the wet when exiting roundabouts and being too enthusiastic with my right foot. The Mk1 only has 122bhp so it's difficult to break traction in the dry. The chassis/handling is brilliantly balanced and tuned, so you don't need much power to have fun. It doesn't have ABS, ESC or traction control so it's an incredibly pure driving experience. It's taught me a lot about driving, especially driving fast in wet weather.

    Shortly after I first bought the car back in 2007, I took it to an MR2 specialist who warned me about over-correction when giving me some driving advice. He said you're more likely to go through a hedge/wall/bus-stop-full-of-children forwards after over-correcting, rather than backwards after spinning. Mid-engine cars require much smaller, quicker and more precise steering inputs, especially when dealing with over-steer. When the weight bias is towards the rear you have to be a lot more careful. Driving my E39 in comparison, oversteer is much more progressive and slower, and easier to predict and control.

    One of my friends races MR2s in real life and helped me with the physics of my MR2 in rFactor2. He also made these videos where you can clearly see the MR2 enjoys tank slapping it's drivers frequently. In fact, the first video begins with a beauty of a tank slapper at the bottom of Paddock Hill Bend at Brands.





     
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  14. Filip

    Filip Registered

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    And the obvious question: is your MR2 mod available for download?
     
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  15. mantasisg

    mantasisg Registered

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    @dylbie Awesome stuff, beautiful to watch, I like cars like that so much. Pretty surely MR2 is a tankslapper car mostly because it's low polar inertia. All cars like that will always be less forgiving, because they are sharper. But it does not always seem to be the case in simulations.

    @Lazza Yeah you are right, thats true full tank slapper when you continue to drift from side to side struggleing to set car straight, and maybe even spinning out finally. But I think that technically the one which sends you out immediately is just simply the same, it is only so brutal that you loose the car with first flick, thats the only difference. But both are because rear tires grips up when fronts aren't set into the proper direction.

    And I disagree that all tires are sliding during the normal oversteer. Only rear tires. If all tires would be sliding it is either 4 wheels drift, which is rather rare and is pretty difficult, or it is a certain spin, or just very very close call by nearly stopping to a halt. My theory is that during normal oversteer you just always have normal or close to normal front end grip if you turn into a slide direction properly (what you say is countersteer). The only grip that goes on/off during normal oversteer is rear end grip.
     
  16. mantasisg

    mantasisg Registered

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    Just some nice, well and some actually terrible... examples to illustrate thread:

    (impressing girl by playing it like it is no big deal)
    (Niels made AMS Miata physics for a friend)
    (0:33 tiny tankslapper, 0:44 partial tanklapper/instant slapper)
    (just recently mentioned MR2, unset by a hump and ended up with tank slapper)
    (most unexpected and most musical tankslapper ever)
    https://www.youtube.com/watch?v=H1VHhyiVXo0 (historic tire has enough grip for that, commentator calls it double tankslapper)
    https://www.youtube.com/watch?v=2DTnZeSQtiU (tankslapper happenign at no grip)
    https://www.youtube.com/watch?v=KfjyXVagtrU (1:34, apparently drivers really do spin MR2 a lot, because the name keeps flashing in the search results)
    https://www.youtube.com/watch?v=I7M9cZkTOns (6:31)
    https://www.youtube.com/watch?v=LPCNKW5JR3I (just the worst, rip)
     
  17. Supa

    Supa Registered

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    My Head hurts!!! Just add some damping ....car dependant aleviates Tank slappers!
     
  18. mantasisg

    mantasisg Registered

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    @Supa Why your head hurts ? I hope you are ok. We are just trying to improve understanding on oversteer mechanics in general.|

    Yeah I suppose the damping of FFB makes difference to how quickly and how precise you can countersteer, or should I say steer out of the slide ? Definitely plays a role.
     
  19. Lazza

    Lazza Registered

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    I knew after I posted that sounded wrong. Indeed front grip loss isn't always the case, only at more extreme angles.
     
  20. Supa

    Supa Registered

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    :)
     

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