2022 cars 'porpoising' at high speed

[djos]

Isn't it possible to use bump stops to prevent the car's bottoming out?? So the floor doesn't choke on the straights??

I got shot down for suggesting that idea a few pages ago.

viewtopic.php?t=30265&start=195#p1042279

I would argue that it's still better to bottom out on the bump stops, than on the floor. You don't have any suspension when riding on the floor either

I agree with you.

[johnny comelately]

Why doesnt the porpoising happen on high speed corners?

[Just_a_fan]

Why doesnt the porpoising happen on high speed corners?

Ant Davidson suggested that it does if the speed is above the "porpoising speed".

[johnny comelately]

Why doesnt the porpoising happen on high speed corners?

Ant Davidson suggested that it does if the speed is above the "porpoising speed".

I just havent seen it, has anyone noticed it?
My thoughts are that it is because of the cornering loading of the suspension

[godlameroso]

I was thinking back to last years slo-mo of the tyres almost having standing waves under some acceleration and curb hopping. I did not mean them being out of balance as that would only 'shake' that corner of the car, not move the whole 'body'

I don't think they're standing waves, the sidewall ripples rotate with the sidewall. They arise from the buckling of the sidewall which is result of the tensile strength of the sidewall and the constant vertical and torsional loads delivered through the wheel. At least not any more than a leaf spring deflecting under a constant load is considered to be a standing wave. The porpoising frequency looks quite slow (maybe 1-4 hz), vibrations from sidewall buckling if felt by the car would be much higher (number of ripples times wheel RPM), hundreds or thousands of Hz.

(not doubting your explanation or the others, but) I have a 'boiler' with a fan that runs at (guess) 5k RPM and the side panel resonates at maybe 200-250 Hz. I don't know this 'shift' in frequency is transferred, I was thinking airflow through the flu, but probably mounts( I put a magnetic knife rack on the cabinet side and it silences it )

Anyway, I have gone far enough off topic now, so thanks everyone for your reply's.

Your thoughts are not without merit, unsprung weight can contribute to hopping.

[NicoS]

W13 at low speed.
https://twitter.com/i/status/1511660258413928454

[Big Tea]

I don't think they're standing waves, the sidewall ripples rotate with the sidewall. They arise from the buckling of the sidewall which is result of the tensile strength of the sidewall and the constant vertical and torsional loads delivered through the wheel. At least not any more than a leaf spring deflecting under a constant load is considered to be a standing wave. The porpoising frequency looks quite slow (maybe 1-4 hz), vibrations from sidewall buckling if felt by the car would be much higher (number of ripples times wheel RPM), hundreds or thousands of Hz.

(not doubting your explanation or the others, but) I have a 'boiler' with a fan that runs at (guess) 5k RPM and the side panel resonates at maybe 200-250 Hz. I don't know this 'shift' in frequency is transferred, I was thinking airflow through the flu, but probably mounts( I put a magnetic knife rack on the cabinet side and it silences it )

Anyway, I have gone far enough off topic now, so thanks everyone for your reply's.

Your thoughts are not without merit, unsprung weight can contribute to hopping.

Thanks. Would it be aggravated by the length of the suspension arm giving it extra leverage as opposed to a road car which would be attached almost vertically above?

[atanatizante]

Could someone please explain if porpoising is influenced by the car`s mass distribution, by the centre of pressure, by the centre of gravity or a combination of all 3 and maybe much more factors than those above mentioned ... Thanks in advance!

[godlameroso]

(not doubting your explanation or the others, but) I have a 'boiler' with a fan that runs at (guess) 5k RPM and the side panel resonates at maybe 200-250 Hz. I don't know this 'shift' in frequency is transferred, I was thinking airflow through the flu, but probably mounts( I put a magnetic knife rack on the cabinet side and it silences it )

Anyway, I have gone far enough off topic now, so thanks everyone for your reply's.

Your thoughts are not without merit, unsprung weight can contribute to hopping.

Thanks. Would it be aggravated by the length of the suspension arm giving it extra leverage as opposed to a road car which would be attached almost vertically above?

The lighter you make the unsprung weight, the faster it can move up and down in response to road imperfections, and on the downside, heavier components can dampen some of the oscillations and hysteresis, whereas lighter ones can enhance them because heavier components have more inertia.

[godlameroso]

Could someone please explain if porpoising is influenced by the car`s mass distribution, by the centre of pressure, by the centre of gravity or a combination of all 3 and maybe much more factors than those above mentioned ... Thanks in advance!

In boats porpoising happens because too much weight in the back, so you use trim tabs, or put passengers in the front to keep the boat level. I feel that there's several factors involved as you say, more than 3, and all contribute to the effect.

I don't think that the problem can be fully solved, but it can be mitigated enough that it won't affect reliability or driver confidence. I think a big part of the solution is minimizing the amplitude of the waves.

[dialtone]

Could someone please explain if porpoising is influenced by the car`s mass distribution, by the centre of pressure, by the centre of gravity or a combination of all 3 and maybe much more factors than those above mentioned ... Thanks in advance!

In boats porpoising happens because too much weight in the back, so you use trim tabs, or put passengers in the front to keep the boat level. I feel that there's several factors involved as you say, more than 3, and all contribute to the effect.

I don't think that the problem can be fully solved, but it can be mitigated enough that it won't affect reliability or driver confidence. I think a big part of the solution is minimizing the amplitude of the waves.

In boats porpoising behaves very differently anyway as it's heavily influenced by waves and, as far as my experience goes with hard-keeled inflatable outboard motorboats, it is actually improved with higher speed as you tend to skid over the waves instead of tilting, thanks to inertia cutting through the wave. I'm certainly ignorant in this area though.

[johnny comelately]

Melbourne FP1 for Sainz, there was (onboard camera) porpoising on a left hander.
It could have been induced in the previous (short) straight, but the cornering loads didnt cancel it out

[vorticism]

leclerc fp2 1.18.978 - porposing like mad on back straight from 270+ kmh. Probably the worst I've seen from ferrari so far. Curiously it doesn't seem to be affecting them much on main straight.
https://streamable.com/09za8i


verstappen fp2 1.19.223 - just getting wrecked in S3 low-mid speed corners. Might have been affected a little by the car in front
https://streamable.com/uxy91h

Great video Juzh. Ferrari porpoising from 270 - 315 kph. The RB smooth through that same section 270 - 320 kph. Ferrari onset is mid-corner so maybe some yaw effects, maybe not.

Note the engine note changes with the porpoising, indicating that there is either a drag/linear acceleration component or the driver's foot is being moved. Also not the Ferrari doesn't porpoise at the same speed on the main straight.

[Big Tea]

Looking at some vids of today, does it seem to anyone else the Merc has a different 'type' of proposing to the Ferrari and RBR? They are Proposing in a sort of sinusoidal wave, but does it look like the Merc is doing it all from the rear dipping?

I have not seen any 'ground level' clips where I can be sure, but what I noticed on a small screen is it is almosr pivoting on a point before the front axle rather than literally like a porpoise.

[johnny comelately]

Serious porpoising at MotoGP at COTA.
In FP2 at the 37 minutes to go mark for Jorge Martin about as bad as it gets before major consequences.