Can someone explain physics of this accident in detail ?

Accident is seen at 1:20. Maybe you know more similar accidents captured on video ?



Mini Cooper rolls after hitting kerb.

I find this very interesting, and I'm trying to understand why it happened.

To begin with I'm wondering how hitting kerb generated so much force to launch inside side of the car so high ? Is it some kind of resonance of front inside, and then rear inside wheel kerb hit ? Is it some fault, lock of suspension, or suspension geometry ? Is it because low susp travel ? Is it because too stiff roll-bar ? Is it because some weird play of dampers ?

 

Sorry, but video playback got stuck at 0:30

It's hard to say really just from the video, but I don't see anything that should prevent this happening, it's probably a combination of different things that resulted in a force big enough to roll the car...

 

It is a little heavy car and very rigid, when passing by the curb the inner wheels have more height and all the weight of the vehicle goes towards the outer side generated by the inertia making it take more grip on these wheels and not allowing them to slip.

You can see videos of the same type with Fiat500 abarth, some day we will recreate this in Assetto Corsa ... Some day.

This was easy to do in netkar namie

 

All I can say is, that physics in real life are really complex. There are so many variables who influence what happens at the end. But in this case I would say its mostly because of the kerb is really high and the spring and damper system is absorbing a lot of energy through the hit. This force have to go somewhere and spring is giving it back and so the car jumps. And if you are on the left 2 wheels and rotating the car to the right then there is a sweetspot where the cars flips.

 

Yes, mostly right. However, you're slightly mixing up what's going on between dampers and springs. Really stiff dampers could make this happen all by themselves. Stiff springs could also do it. The physics of what's actually going on is a bit different in the two cases though. (Stiff dampers would prevent the wheel moving much relative to the chassis, and basically this would force the whole chassis up when the wheel hits the kerb.)

 

@dermonty But the dampers should slow dawn the compression, and extension of the spring too. Also the kerb doesn't look extremely high, medium maybe.

@Neilski Ninjad, I also think whats the difference in the pace of motion in this case. It must be fast_bump thing to hit the kerb, an I see that some cars in AC has separate sliders for fast bumps. So maybe very stiff fast bump, or very soft fast rebound ?

 

The bluecar by blocking the path forced human steering & the front roll + the rotational inertia force made the rear ARB rear tire load grip created a higher the center of gravity which resulted flip.

 

well, it looks like the car is quite top heavy. So with racing suspension being quite stiff and springy at the same time, taking that kurb indeed caused it enough to put too much force on the left side on the car, which causes the center of gravity to shift it all to the left side. Hence this result

 

It has a relatively high center of gravity and short track width, so in hard steady-state cornering, it's not going to be in particularly stable equilibrium - it's at a disadvantage to start. Hitting the curb allows the car to get up onto two wheels, making a situation where the outside wheels act as a pivot point. Once the centripetal force from the tires reaches a certain point, the torque caused by gravity can be overcome and allow the car to roll over.

 

kerb of death....fix in next update.

 

Same as this one:

Both guys were much too fast in the corner and hit the inside curb. If you try it in your own car, chances are you might get the same result whatever the dampers :B

 

If you look closely start of the kerb is quite steep and goes up *a lot*, so it works like a ramp used in stunts. As i see it it's not the dampers (or springs) being too hard but rather the bump too big, also you'd have to have above critical (fast) damping to see significant increase in jumpiness.

The jump up is caused mostly by rear left getting compressed from the significant roll moment created at front right while climbing the kerb. It's not really a resonance, same thing happens to table if you put a rock under one leg. Also rear right going up a the kerb helps, but is not required for this kind of jump to happen.
Then as the front continues to fly up on inertia, rear is pushed upwards by compressed spring which results in a jump up. Rest comes from track having a lot of camber and still rising as well as the delay on jump in the rear causing oversteer on landing.
I'd say most cars with "sporty" suspension could jump like that. It's down to springs/chassis being stiff/strong enough to store enough energy in compression, instead of bending.

ps: And if we take stiffer suspension ...

 

a relatively small negative vertical load at the point of maximum weight transfer

https://driver61.com/uni/weight-transfer/

 

Looks perfectly reasonable to me. The weight of the car has already shifted to the left before hitting the kerb.

When the right wheels hit the kerb that side of the car is pushed up easier as all the weight has already shifted to the outside of the car. So then as the right wheels leave the ground even more weight transfers to the left hand side which actually gives more friction between the tyre and the tarmac, helping it grip to actually encourage the rollover.

Then conservation of angular momentum does the rest!

 

I think that Kerb is not that steep, not the flattest one maybe, but I don't think it has much of ramp effect there, maybe a bit, but the whole accident is more like a trampoline action, I think. Interesting point about left rear wheel being compressed, haven't paid much attention to it before, mostly looked at the inside wheel.. But yeah, I can see now, front right goes high up very suddenly, compresses rear and especially rear left so incredibly much that it bounces up. Interesting to see that both rear wheels are off the ground for brief moment, and when it comes down there is second compression happening, and then the extension into oversteerish slide, which probably was caused by that short moment of rear wheels being in the air. Interesting isthat left rear susp extensions didn't result in saving the car from roll over, but more like the opposite. Also it is interesting how that part of tire had a capability to keep some grip, can be seen nicely from the skidmark, which follows the curve nicely. I suppose he would have gone straight, he wouldn't have rolled over, but maybe he couldn't as he was sliding struggling to get grip.

I think that is not entirely true for the first phase (when car is still not on four wheels, or inside wheels are not very high up), because weight doesn't shift, though it is called weight transfer, but what really shift is load, of course some of weight may also transfer, I think weight shift is directly tied to coG shift, so as there is still little CoG shift the only thing that really transfers is the load. But I think the same like you for the second phase when inside wheels are high up.

I think that the weight which hits the curbs of the inside actually creates that much upwards force, and energy to accelerate that side of the car upwards. I don't think that it is only ramp effect, more like trampoline and a little bit of ramp too.

 

I suppose weight shift is not the correct term, more that there is more force on the outer wheels. Technically weight is just a force. Mass is just mass, what we think of as weight is just the force on a mass due caused by gravity, in this case we mean that the weight is added to by an additional force on the outside wheels caused by cornering, and of course it then follows that the opposite effect is experienced on the inside wheels. So in a sense the outside of the car IS heavier and the inside IS lighter before we actually hit the kerb.

 

Yeah, I just watched it frame by frame and I think the left rear lifting was crucial. When I watched it the first time I wondered what had induced the oversteer but yes, the left rear lifting off the ground, just for a moment, allowed the rear to step out and that essentially tightened the turn from the car's point of view, increasing the torque trying to roll it.

I do think the driver could have saved it pretty easily if he had only countersteered - the video makes it look like he didn't even try to do so. I know it all happened pretty fast but still...

 

He was too fast when hitting the cornerstones. Right side springs get compressed, then must release again of course, making the right side lift, and downforce interrupted, think of it as a "reverse stall". Since he was too fast, and turning, G forces slowly flipped over the already lifted right side of the car, et voila. No secrets there.

I recently saw another video by pro-driver Steffen Seyffahrt where he evaluated laps done by players, and time and again he stared in disbelief and told people that they were driving too fast were braking too aggressively, and should use pedals smoother, not so abrupt, and be less aggressive. And he was talking about drivers /players NOT flipping over. I can only imagine what he would say to this one in this video.

Too fast over the curbs. Thats the summary.

 

LOL! Those cars look as though they have net lift, not downforce

 

Yes, thats why I said downforce INTERRUPTED, and what I mean by saying "reverse stall".

The net lateral forces without the jump over the curbs probably would not have made the car overutrning. The hop however elevated two of the four contact points, also lifted the car's base plat, and however low compared to formula cars the downforce from that plate on such a car is - it is there, just not as excessive in net effect as in said formula cars. As long as the net lateral force is lower than the net downforce, the car stays on all four wheels, maybe will slide, but will not overturn. When the laterla force exceeds downforce vector - then it overturns.

I think of it in force vectors. These cars have no explicit lift vector, like an aircraft's wing is designed to intentionally create.

An aircraft stalls if the flow of air over the wing is not sufficiently faster than the stream of air under the wing, yoiu then have not the effect of the vacuum over thwe wing sucking the wing upwards, because then the delta between both streams of air can no longer equalise and surpass the force created by the mass of the plane which makes it wanting to drop down (downforce vector). Thats why I ironically comparerd the car acicdent to a stall, calling it a reverse stall. Dont take it too serious, though, it was meant more as a funny term.