25 replies to this topic

[mariner]

As an F1 fan who can remember when ground effects arrived the current "porpoising and bouncing" rows do make me smile - History seems to be repeating itself - Lotus 78 with side brushes raised cornering speeds a lot - the Lotus 79 with sliding skirts showed the full GE potential . So the rule makers  banned skirts and the teams lowered the cars to within millimetres of the track - Rule makers set a minimum ride height but teams developed hydraulic cheat systems . So drivers still kept being  shaken to pieces So finally the rule makers gave up on GE and said flat bottoms.

 

 

 

Now its al repeating itself - except for one thing - wheel size.

 

 

 

Along  with the new aero rules the 13 inch wheels  , and so fat sidewall tyres, were swapped out for 18 inch wheels and "modern" low profile tyres .for 2022.

 

 

 

Now the team’s dynamics guys have struggled for years with how to control a suspension where much of the movement was in externally undamped high sidewalls but now - I presume(?) that the sidewall flexing is reduced so the dynamics guys can control ride height mainly through the springs and dampers. Or to put it another  way the previous vey hard springing is now getting straight through to the track surface. 

 

 

 

So is it just possible that the villain in all this is the change in controlled suspension frequency and that is why the bouncing has gotten worse?

 

 

 

If you couldn’t control the flexible  bounce in the old , high , sidewalls the cars had a cushion. Now you can lock the suspension up nearly solid and banish most bounce?

 

As a last comment , putting aside the "handbag " squabbles of messrs. Horner and Wolf I think the FIA has probably screwed up badly here and given alt eh aero CFD stuff they ran ran to design GE for better overtaking they should have forseen this issue way back.

Edited by mariner, 21 June 2022 - 09:07.

[Charlieman]

Don't underestimate the damping properties of a high sidewall tyre. The steel, plastic and rubber create a composite with complex properties. However modern dampers are very clever and motor sport engineers in other categories have used low profile tyres for yonks.

 

Porpoising, a consequence of changing downforce levels, was entirely predictable, of course. We can split it into two effects: high frequency sprung vibration and/or situations in which the car is effectively unsprung.

 

When porpoising occurred with 1980s high sidewall tyres, it was resolved by better skirts (when permitted), venturi profiles providing more consistent downforce plus a few aero tricks using vortices. Today's engineers have more tools to play with.

 

Perhaps some teams misunderstood the nature of the two rule changes and their interactions, for which the FIA cannot be blamed.

[mariner]

Adrian Newey made a point somewhere that the teams ( and I assume the FIA) always look at statics when doing tunnel runs and CFD. Their desire to get lots of data meant they run at small changes in ride height etc. but not  letting   the car move inn the tunnel - or maths.

 

I have to assume he knows his stuff so he seemed to be implying the teams and the FIA should have thought through things a bit more deeply.

 

That contradicts my very limited understanding of aircraft stability theory  where statics were assumed to be the giude to dynamics but maybe flutter was an exception like porpoising..

 

If we accept your last sentence, which seems very fair,  then Horner is right - it's team problem not a rules problem.

[Ross Stonefeld]

What's the civilian's explanation for why this hasn't been a problem in Indycar? Is it just the general pragmatism of US racing where they understand their racetracks are bumpy and have irregular pavement so they don't run the the extreme ride heights and damper settings that the theory would tell them to?

[gruntguru]

Adrian Newey made a point somewhere that the teams ( and I assume the FIA) always look at statics when doing tunnel runs and CFD. Their desire to get lots of data meant they run at small changes in ride height etc. but not  letting the car move inn the tunnel - or maths.

 

This nails it. It is difficult to design a high DF ground effects underbody that does not have a positive feedback loop i.e. DF -> ride height reduction -> greater DF ->  greater ride height reduction . . . 

 

The above is an oversimplification because the relationship between pitch, rake and DF (and similar feedback loops) is also key to the porpoising.

[MikeTekRacing]

What's the civilian's explanation for why this hasn't been a problem in Indycar? Is it just the general pragmatism of US racing where they understand their racetracks are bumpy and have irregular pavement so they don't run the the extreme ride heights and damper settings that the theory would tell them to?

my guess is that they are not trying to achieve the same crazy levels of downforce F1 does

[Ross Stonefeld]

They want as much as they can though? It's much easier to have a less sensitive car with a spec supplier, but even in the old days of more open competition they didn't seem to run into this particularly F1 engineering cul-de-sac.

[GregThomas]

Mariner has a point imo that the tyres have a major role in the problem.

 

A friend of mine who was involved at the top level of motorcycle racing for years has told me that in the years since he retired he's sure the tyre manufacturers have introduced some form of carcase damping. The patter problems that were endemic for some time have disappeared. Bikes that pattered on tyres of that period, are now transformed on current rubber.

There's every reason to suppose that if this is true, the same developments have occurred in cars. Very possibly the high sidewalls in use forced some type of development in cars which then went over to bikes. 

It's supposition of course as even with his contacts he's not been able to get any confirmation of his theory

 

It will be interesting to see if the suppliers come out with tyres of possibly a different construction to those in use now..

[desmo]

The amplitude of the tire's elastic modes must be a lot smaller though now due to the smaller volumes. I assume the control of tire damping through material hysteresis and construction is well-understood by tire engineers at this point (well, as much as anything about tires is) . It looks to me on video like the porpoising is occurring in the sprung masses and not in the tires. 

 

As long as even one team is on top of the porpoising issue under the current regs, I don't think the FIA should be trying to help the teams who aren't, in the spirit of fair competition. Figure it out dummies!

[Henri Greuter]

 

As an F1 fan who can remember when ground effects arrived the current "porpoising and bouncing" rows do make me smile - History seems to be repeating itself - Lotus 78 with side brushes raised cornering speeds a lot - the Lotus 79 with sliding skirts showed the full GE potential . So the rule makers  banned skirts and the teams lowered the cars to within millimetres of the track - Rule makers set a minimum ride height but teams developed hydraulic cheat systems . So drivers still kept being  shaken to pieces So finally the rule makers gave up on GE and said flat bottoms.

 

 

 

Now its al repeating itself - except for one thing - wheel size.

 

 

 

Along  with the new aero rules the 13 inch wheels  , and so fat sidewall tyres, were swapped out for 18 inch wheels and "modern" low profile tyres .for 2022.

 

 

 

Now the team’s dynamics guys have struggled for years with how to control a suspension where much of the movement was in externally undamped high sidewalls but now - I presume(?) that the sidewall flexing is reduced so the dynamics guys can control ride height mainly through the springs and dampers. Or to put it another  way the previous vey hard springing is now getting straight through to the track surface. 

 

 

 

So is it just possible that the villain in all this is the change in controlled suspension frequency and that is why the bouncing has gotten worse?

 

 

 

If you couldn’t control the flexible  bounce in the old , high , sidewalls the cars had a cushion. Now you can lock the suspension up nearly solid and banish most bounce?

 

As a last comment , putting aside the "handbag " squabbles of messrs. Horner and Wolf I think the FIA has probably screwed up badly here and given alt eh aero CFD stuff they ran ran to design GE for better overtaking they should have forseen this issue way back.

 

 

I would like to add two more differences  between the cars of then and now and what might affect teh current cars more:

 

1) way larger wheelbase and length of the current car and related with that:

2) The weight difference between the two kind of cars

.

[Ross Stonefeld]

The amplitude of the tire's elastic modes must be a lot smaller though now due to the smaller volumes. I assume the control of tire damping through material hysteresis and construction is well-understood by tire engineers at this point (well, as much as anything about tires is) . It looks to me on video like the porpoising is occurring in the sprung masses and not in the tires. 

 

As long as even one team is on top of the porpoising issue under the current regs, I don't think the FIA should be trying to help the teams who aren't, in the spirit of fair competition. Figure it out dummies!

 

Indeed. If your car was designed/manufacturered/maintained in a way that made it dangerous the FIA would black flag you. The rules are not inherently dangerous, any more than any random aerodynamic regulation. If you screw it up that's on you. If you run your car in areas where it doesn't work or isn't reliable or is hard to drive, that's on you. 

[Fat Boy]

What's the civilian's explanation for why this hasn't been a problem in Indycar? Is it just the general pragmatism of US racing where they understand their racetracks are bumpy and have irregular pavement so they don't run the the extreme ride heights and damper settings that the theory would tell them to?

IMO, sort of.

Porpoising is generally produced through a combination of aerodynamic ride height sensitivity and ride control. You can't just crank a bunch of damper in the car and make it go away. The pragmatism of Indycar racing means that the aero platforms of the cars have to deal with ride heights from ovals to street courses. By necessity, the front ride height sensitivity has to be limited or the car wouldn't work effectively across the various tracks raced in Indycar. F1 car are likely more optimized for a lower ride height and they likely have significant sensitivity to (particularly front) ride height variation. They can raise the front of the car and the porpoising will go away, but, in doing so, they'll have to run a ride height sensitive car in a range for which it is not optimized. The teams and drivers are making a conscious decision to accept as much of the bouncing as they can in an effort to maintain as much downforce as they can. If the FIA wanted to make a rule that the accelerations due the porpoising cannot exceed X, then I think that would be a great way to protect the driver. Certain cars would be legislated uncompetitive in this scenario, though, which is apparently not acceptable. Draw your own conclusions, but it all has a very NASCAR feel to me.

[Wuzak]

If the FIA wanted to make a rule that the accelerations due the porpoising cannot exceed X, then I think that would be a great way to protect the driver. Certain cars would be legislated uncompetitive in this scenario, though, which is apparently not acceptable. Draw your own conclusions, but it all has a very NASCAR feel to me.

 

It seems that is what the FIA intends. They already have the G-meters on board for crash monitoring, so all they have to do is work out the criteria.

[Fat Boy]

It seems that is what the FIA intends. They already have the G-meters on board for crash monitoring, so all they have to do is work out the criteria.

I'm curious whether they dictate an aerodynamic change which reduces the accelerations or whether they use the existing data monitoring to police thresholds. It will be interesting to see their approach.

[RedRabbit]

Higher side walls would probably contribute to more uncontrolled porpoising, with more difficult to control damping.

I'd expect that Indycar uses a different suspension system to the current F1 regulations. As said before, if F1 cars still used the complex, expensive hydraulic systems from last year, we wouldn't know anything about porpoising.

In that essence, I suppose it actually is a failure of the regulations somewhat, in that suspension regulations have been overly simplified.

Active suspension would be a step to far, but an additional spring or damper would help control the suspension compressing to far or lifting too quickly.

Red Bull have probably found a way to simulate this with their pre-season rear suspension upgrade.

[Fat Boy]

Higher side walls would probably contribute to more uncontrolled porpoising, with more difficult to control damping.

I'd expect that Indycar uses a different suspension system to the current F1 regulations. As said before, if F1 cars still used the complex, expensive hydraulic systems from last year, we wouldn't know anything about porpoising.

In that essence, I suppose it actually is a failure of the regulations somewhat, in that suspension regulations have been overly simplified.

Active suspension would be a step to far, but an additional spring or damper would help control the suspension compressing to far or lifting too quickly.

Red Bull have probably found a way to simulate this with their pre-season rear suspension upgrade.

 

I have to applaud the consistency. You're incorrect on every point, lol.

 

1. We can't damp our way out of porpoising. This is an aerodynamic instability, not a mechanical one. The tire stiffness will affect the frequency at which the bounce happens, but it won't dictate whether or not the behavior is present.

2. Ummm, no. We can't damp our way out of porpoising.

3. Seeing as some car have gotten it correct, the failure is not to be found in the regs.

4. The suspension motion due to porpoising is a symptom, not a cause. Again, we cannot damp our way out of porpoising.

5. A suspension upgrade would not fix the porpoising, because it did not cause the porpoising.

[mariner]

Peter  Wright has done amateur commentators like me a big favour by writing an article about the origins of porpoising with the Lotus 80 in the latest issue of Racecar Engineering.

 

As ever with Mr Wright concise, clear and illuminating.

 

He makes plea for the return of active suspension if it becomes real issue and suggests that engineers with log experience like Adrian Newey might have les caught out by the risk of porpiosing with venturis back.

Edited by mariner, 01 July 2022 - 17:23.

[Fat Boy]

Peter  Wright....suggests that engineers with log experience like Adrian Newey might have les caught out by the risk of porpiosing with venturis back.

Tunnels are generally less sensitive than a flat bottom, because designers are consciously keeping the flow organized through the tunnel to maintain downforce. They are much less prone to the choke/flow/choke/flow/ect harmonic we see during porpoising.

 

An active suspension could make sure the car doesn't time in that nasty portion of the aerodynamic ride height map, but it doesn't change the fact that this portion of the ride map exists.

[Ross Stonefeld]

 

He makes plea for the return of active suspension if it becomes real issue

 

Engineers gonna engineer

[Fat Boy]

Engineers gonna engineer

Ya, this would be pretty gratuitous justification for active suspension.

[Bikr7549]

Ya, this would be pretty gratuitous justification for active suspension.

I‘d agree with this-they need to fix the problems they have with what they have.

However, all the clamoring for active is I think justified from the perspective of F1 being the intended pinnacle of technolog, it should have the latest ideas, tho the ideas may be decades old. I‘ve stopped looking at the RC forum thread on this topic, never addressed is the cost and leadtime needed to bring this aspect into play-not insignificant for either. And, this hard/software would certainly bring its own problems into play, which wont be easy or quick to fix either.I would also suggest along these lines that active aero would be fitting for F1. Restricted in some ways certainly, but not with the rigidity of current DRS. More time and $ but if F1 wants to be relevant to the road cars somehow both of these are in the right direction.

Edited by Bikr7549, 01 July 2022 - 23:54.

[Fat Boy]

The 1990's active was really crazy with all the hydraulic messes and mazes they had. It seems like a lot of added complexity for not much payback. I think we've kind of learned to mimic many of the actions of the old active systems. 

 

 

It's entirely possible to have a suspension which is partially active by allowing magnetic dampers or something like that. It would be interesting to see what control strategies would emerge from those regs.

[Wuzak]

He makes plea for the return of active suspension if it becomes real issue and suggests that engineers with log experience like Adrian Newey might have les caught out by the risk of porpiosing with venturis back.

 

Wasn't Newey involved in the design of the Aston Martin Valkyrie?

 

I believe that has venturi tunnels, and Newey may have learned (or remembered) some things about it.

[desmo]

Mandating passive suspension feels like mandating pushrod engines in NASCAR. It *feels* like a cost-saving thing, but teams are going to spend whatever they can get their hands on.

 

At some point, active or semi-active will surely be cheaper and easier than hauling around gear and hiring experts in steampunk springs-dampers-ARBs. Imagine racing without drivers complaining about their teams' locked-in raceday suspension set-up mistakes.

[Fat Boy]

Mandating passive suspension feels like mandating pushrod engines in NASCAR. It *feels* like a cost-saving thing, but teams are going to spend whatever they can get their hands on

At some point, active or semi-active will surely be cheaper and easier than hauling around gear and hiring experts in steampunk springs-dampers-ARBs. Imagine racing without drivers complaining about their teams' locked-in raceday suspension set-up mistakes.

I know it's a promise that often fails to deliver, but I bet if MR tech came to a couple higher forms of racing that we'd see massive advances in the matter of a couple years. Right now, the evolutionary pressure is heavily tilted towards luxury ride, but if it were suddenly allowed in F1 or WEC, the shift towards performance could happen overnight and I bet it would improve a whole generation of cars.

 

Your assumptions on steampunk damper work is more accurate than you know, but I don't give you trouble for glass-work...

[MattPete]

The new tires aren't really that low profile.  IIRC, they are only slighly lower profile than Indycar tires.   What has grown is the overall tire diameter.

 

I think the real screw-up is the increase in unsprung weight.  Instead of going from 13 to 18 inches, they should have tried something more modest, like 15 or 16 inch wheels. They could have kept the same overall diameter, which would have curtailed the current visibility problems, and had a lower unsprung weight, which leads to better braking, acceleration, and handling/ride over bump surfaces.