Discussion - is there a design issue with LMP

[MulsanneMike]

Originally Posted by Purist

The old prototypes (Ford GT40, Porsche 917, Ferrari 512) were and are considered to be notoriously unstable, so that doesn't seem like a good road to go down (low downforce/low drag). Even as far back as the 1930s, only a selct few drivers were ablt to REALLY handle cars that had a tendency to oversteer (the best were Rosemeyer, Nuvolari, and Stuck in the hill climbs).

You guys might want to check MulsanneMike's latest site update. Among other things, it mentions that critical take-off speed while going backwards (180 degrees yaw) has gone from 281km/h (174.6mph) with the LMP900 regs to 500km/h (310.7mph) with the LMP1 regs. However, critical take-off speed while going sideways (90 degrees yaw) has dropped from 282km/h (175.2mph) for the LMP900 regs to just 192km/h (119.3mph) for the LMP1 regs. That right there is the real problem. The LMP900s didn't have such a dramatic drop-off in downforce going through the various degrees of rotation.

I might also mention tha I'm quite certain that the Peugeot had lifted the right side off before it encountered the grass, and was dragging the left front tire on pavement the whole time before the car was fully off the ground.

Finally, I'll take another look, but I think the camera zoom made it look like the Peugeot was much closer to the top of the fence than it really was, so I'm not especially concerned about the cars clearing debris fences at this juncture.

Re-read what I wrote. Current LMP1's CTS is 282 km/h @ 45 degrees to 192 km/h @ 90 degrees. I didn't say that was a comparison LMP1 to LMP900 as insinuated here. In fact the CTS figures are much lower for the old-rules LMP900s (that is, they generate substantially more lift in yaw and are at higher risk of liftoff), the LMP1 new-rules-cars have in fact increased the CTS in yaw quite a bit and the numebrs quoted above are for them and them only. I didn't quote any CTS figures in that article for LMP900s @ 45 or 90 degrees, only 180 degrees.

[JAG]

Originally Posted by MulsanneMike

Not sure where I see total downforce levels playing any part into the equation. The problem is that the shape of the cars in cross section promotes lift that counteracts car weight when large yaw angles are encountered. Point of fact is that the cars aren't meant to travel sideways!

IMO, it's two fold, cars need to be slowed and the lift problem needs to be addressed.

1. You can slow cars by 5 seconds a lap at Le Mans to stand still, they'd still qualify under 3.30 and race around 3.30+ in '09. Or you can slow them by 10 seconds a lap so the manufactuers have 2-3 years development ahead, without the hassle of reg tinkering, before another major change is needed.

2. The Porsche curves are quick, but the cars are only travelling at 160mph-180mph, a car going sideways should not take off in this day and age. Only recently did we see the rear wing strakes introduced to WRC cars, this ensured cars did not lose downforce when sliding on gravel, so obviously knowledge of aero when a car is side-on is still limited.

Is it not possible to introduce roof/body flaps like NASCAR, even some kind under the car. Or reduce the size of the underfloor with tunnels, stepped floors etc.

[Purist]

Fair enough. I think I was just following on autopilot following your 180 degree figures.

[Fogelhund]

Originally Posted by JAG

IMO, it's two fold, cars need to be slowed and the lift problem needs to be addressed.

1. You can slow cars by 5 seconds a lap at Le Mans to stand still, they'd still qualify under 3.30 and race around 3.30+ in '09. Or you can slow them by 10 seconds a lap so the manufactuers have 2-3 years development ahead, without the hassle of reg tinkering, before another major change is needed.

2. The Porsche curves are quick, but the cars are only travelling at 160mph-180mph, a car going sideways should not take off in this day and age. Only recently did we see the rear wing strakes introduced to WRC cars, this ensured cars did not lose downforce when sliding on gravel, so obviously knowledge of aero when a car is side-on is still limited.

Is it not possible to introduce roof/body flaps like NASCAR, even some kind under the car. Or reduce the size of the underfloor with tunnels, stepped floors etc.

What you say is interesting, and certainly everybody wants things to be as safe as possible. When you suggest that the cars need to be slowed, and that all of these incidents are isolated strictly to lift issues with the cars, which studies, or evidence are you citing to back this up? This figure of five seconds per lap, is this an exact number that once achieved will ensure that all cars stay on the ground? How was this conclusion of five seconds reached?

[Purist]

I have to agree Fogel. Also, given that the cars are so far beyond that critical threshold for take-off when approaching 90 degrees of yaw, 5-10 seconds a lap at Le Mans is rather academic, as would be any proposed track changes there or elsewhere (and on that last note, don't screw up any race tracks more than they already have been, fix the cars).

On a somewhat related point. NASCAR machines can and do still lift off, very spectularly sometimes even (as in the case of Michael McDowell). Yes, that was a different root cause, but the risks posed to the driver and others are quite similar, plus the stock cars are much heavier.

[JAG]

Originally Posted by Fogelhund

What you say is interesting, and certainly everybody wants things to be as safe as possible. When you suggest that the cars need to be slowed, and that all of these incidents are isolated strictly to lift issues with the cars, which studies, or evidence are you citing to back this up? This figure of five seconds per lap, is this an exact number that once achieved will ensure that all cars stay on the ground? How was this conclusion of five seconds reached?

Cutting speeds is not neccessarily to stop the cars getting airbourne, but as part of an overall revision of the regs.

The increase in speeds over the last few years is almost entirely down to increased cornering speeds, acceleration/braking is very similar between a 908 and any P1 from the last 10 years. It's the cornering speeds the ACO fears, and these can be cut by reducing downforce. These days you can visibly see how much quicker the cars are through the bends than in previous years.

You have a choice, do you tweak the cars a little each year to bring them back to 2006-7 speeds, or do you make fairly radical changes to give the cars a lttle headroom for development.

If the latter it makes sense to totally rethink the aero to reduce the problem of cars getting airbourne (i.e the proposed, more radical, EVO regs), if the former your seriously limited to the changes you can make, unless someone discovers a flap here or tweak there reduces the airbourne problem.

[Fogelhund]

Let me ask again JAG; what data/studies are you using, to determine that something needs to be done? Which research that you've read, or which data have you computed on this? Which incidents in particular are solely due to the car and which incidents are due to other conditions, such as surface, elevation changes......?

[HORNDAWG]

How about the fact that there has been a (relative) rash this year of cars, regardless if there is any outside influence as an instigator, that have become airbourne in a 90º yaw or pasing through it. And that is a hazard to the drivers, as well as the possibility, if not probability, of an accident where spectators are involved. The question is if there is an amicable/affordable solution that will not totally castrate the cars?

L.P.

[JAG]

Put it this way, if you point to surface and elevation changes as the reasons for cars getting airbourne, at tracks that have been used for many years, and in the case of Monza by many different formulas, there's something flawed in the design of the cars.

We aren't talking major elevation changes like the old Mulsanne hump, every circuit has similar, minor, elevation changes, which implies LMP's are liable to take off at most tracks around the world!

Reducing laptimes and cornering speeds is a side issue to the airbourne problem, but you can deal with both together, either by re working current cars, or designing a new car from scratch.

PS, Hughes De Chaunac has said there is an aero problem with the cars when not pointing in the intended direction, while Nick Wurth at Acura has been investigating what happened in the recent incidents, indicating an aero issue (big or small), rather than the cars being a victim of the environment.

The question is if there is an amicable/affordable solution that will not totally castrate the cars?

Theres no reason to think not, relatively simple aero changes could transform the cars, afterall F1 and Champ Cars are much quicker than an LMP1, while stockcars race week in, week out at 180mph plus with few airbourne incidents.

[Fogelhund]

Originally Posted by JAG

Put it this way, if you point to surface and elevation changes as the reasons for cars getting airbourne, at tracks that have been used for many years, and in the case of Monza by many different formulas, there's something flawed in the design of the cars.

We aren't talking major elevation changes like the old Mulsanne hump, every circuit has similar, minor, elevation changes, which implies LMP's are liable to take off at most tracks around the world!

Originally Posted by HORNDAWG

How about the fact that there has been a (relative) rash this year of cars, regardless if there is any outside influence as an instigator, that have become airbourne in a 90º yaw or pasing through it. And that is a hazard to the drivers, as well as the possibility, if not probability, of an accident where spectators are involved. The question is if there is an amicable/affordable solution that will not totally castrate the cars?

L.P.

All of this means nothing. The obvious is there is no data, no evidence and nothing of scientific meaning. A few incidents, which have many variables involved, and we've tossed them all into the same bucket, ignoring outside forces. So, we've got a multiple page thread, declaring that this needs to be done, or that needs to be done, and the vast majority are basing this on absolutely nothing of relevance, and little knowledge on the subject. I'm not saying that I am more qualified to know more about this, as I don't, but I'm not going to pretend that laps times need to be slowed by 5 seconds, or this, or that. If Nick Wirth has data that shows that there have been specific issues, and a solution, fair enough, but I doubt he'll be posting that here.

Most of the incidents have involved cars in the grass, at times the grass has had elevation issues.... It's all the fault of grass... pave the world..

Typical knee jerk reaction when a series of events occur, when previously there wasn't issues. Let the experts determine which events are cause of inherent flaws in LMP's, and we should stick to being fans.

[JAG]

Let the experts determine which events are cause of inherent flaws in LMP's, and we should stick to being fans.

As a fan I'd let them run loose with 1000bhp, but in this day and age you have to consider outside forces and be responsible.

I don't care for 'green issues' either, but as a fan I take an interest with regards to Le Mans because alternative fuels is an opportunity for this form of racing to prosper and entertain us, while other forms of the sport come under pressure from the green lobby.

Pure selfishness to ensure my hobby has a healthy future.

Slowing the cars is not my idea, the ACO will do it regardless, they consider current speeds (3.22 qualifying lap) to be at least 5 seconds too quick for what they consider safe.

The above will happen regardless, so it's a good time to consider killing two birds with one stone by addressing the airbourne issue as well.

If an LMP cannot spin at 150mph+ anywhere but a smooth, paved area, something, maybe relatively simple, needs to be changed on the cars, afterall you don't see these problems with quicker F1 cars, or almost as quick, flat bottom, DTM machines.

[HORNDAWG]

Originally Posted by Fogelhund

All of this means nothing. The obvious is there is no data, no evidence and nothing of scientific meaning. A few incidents, which have many variables involved, and we've tossed them all into the same bucket, ignoring outside forces. So, we've got a multiple page thread, declaring that this needs to be done, or that needs to be done, and the vast majority are basing this on absolutely nothing of relevance, and little knowledge on the subject. I'm not saying that I am more qualified to know more about this, as I don't, but I'm not going to pretend that laps times need to be slowed by 5 seconds, or this, or that. If Nick Wirth has data that shows that there have been specific issues, and a solution, fair enough, but I doubt he'll be posting that here.

Most of the incidents have involved cars in the grass, at times the grass has had elevation issues.... It's all the fault of grass... pave the world..

Typical knee jerk reaction when a series of events occur, when previously there wasn't issues. Let the experts determine which events are cause of inherent flaws in LMP's, and we should stick to being fans.

Ya, knee jerk reactions. Some things do not need a 5yr, 3000pg study to determine there is something wrong. But it might need a little bit of thought on how to minimize it happening without destroying a good thing. And frankly, the all or nothing references, are blasé.


L.P.

[MulsanneMike]

Originally Posted by JAG

Put it this way, if you point to surface and elevation changes as the reasons for cars getting airbourne, at tracks that have been used for many years, and in the case of Monza by many different formulas, there's something flawed in the design of the cars.

We aren't talking major elevation changes like the old Mulsanne hump, every circuit has similar, minor, elevation changes, which implies LMP's are liable to take off at most tracks around the world!

Reducing laptimes and cornering speeds is a side issue to the airbourne problem, but you can deal with both together, either by re working current cars, or designing a new car from scratch.

PS, Hughes De Chaunac has said there is an aero problem with the cars when not pointing in the intended direction, while Nick Wurth at Acura has been investigating what happened in the recent incidents, indicating an aero issue (big or small), rather than the cars being a victim of the environment.



Theres no reason to think not, relatively simple aero changes could transform the cars, afterall F1 and Champ Cars are much quicker than an LMP1, while stockcars race week in, week out at 180mph plus with few airbourne incidents.

This is misleading as none of the cars has become airborne because of an elevation change. They've become airborne because they have yawed unexpectedly (mostly due to mechanical failure) while at or near maximum speed. Off track topography only gets a mention because it doesn't help in bleeding off velocity. And velocity is the great enemy in a yawing situation.


The suggestion that this is a new phenomenom is wrong as well. I have a list compiled by Yoshi Suzuka that cites incidents as far back as '66. The list is by no means comprehensive and he has only 20 incidents on it of which only 4 occured within the past 10 years.

[Purist]

DTM cars run sprint races, and thus are generally not afflicted with many of the mechanical failures we have looked at here. Also, they have significantly less horsepower than LMPs (lower straight-line speed) and weight substantially more (harder to produce enough lift to take off).

Open-wheelers have significantly less undertray area, but the IRL has shown repeatedly that you can get it very wrong with those sort of cars.

Given critical take-off speed, I would have to say that the grass, curbing issue is a relative red herring. Also, the Mazda's front bodywork was not firmly in place when it took off at Sebring. Air getting under that bodywork is a likely culprit in that situation, and something that would be nigh impossible to alleviate. I mean, you can design the aero package to do certain things, but if that package in inadvertantly altered at speed (so it doesn't function properly, or at all), what can you really do?

After 40-some years of fighting this issue, I suspect that with sportscars any package will have trade-offs. By that I mean that you may be able to get improvement in some areas, but will have to accept sacrifices in others for those gains.

Something else occurs to me, MulsanneMike, could the overall aspect ratio of LMP1s be a problem in and of itself?

[Speed-King]

Originally Posted by Purist

DTM cars run sprint races, and thus are generally not afflicted with many of the mechanical failures we have looked at here.

Audi had quite a big problem with failing front suspensions 2 or 3 years ago, as they had designed them too weak with too much weight reduction in mind. It resulted in so me bad race results for them, however I can't remember those failures causing a severe crash.

[Purist]

You'll have to forgive me, but I've only seen highlights from the 2006 and 2007 DTM seasons, courtesy of SPEED (which I only get when I'm off at the university).

[Tom87]

Originally Posted by Purist

Something else occurs to me, MulsanneMike, could the overall aspect ratio of LMP1s be a problem in and of itself?

If you treat the cars as an aerofoil when at 90 degrees yaw, they have a large aspect ratio (compared to other cars), but my understanding is that this will only reduce drag rather than increase lift.

[JAG]

Originally Posted by MulsanneMike

This is misleading as none of the cars has become airborne because of an elevation change. They've become airborne because they have yawed unexpectedly (mostly due to mechanical failure) while at or near maximum speed. Off track topography only gets a mention because it doesn't help in bleeding off velocity. And velocity is the great enemy in a yawing situation.

This is my view also, the cars are the resaon for the airbourne incidents, but others believe it's the surface etc., either way, IMO, more needs to be done, not neccessarily radical changes

Your unlikely to stop these incidents altogether, but the latest regs have stopped cars backflipping, I don't think it should be beyond the ACO/manufactuers to make the cars even less sensitive to becoming airbourne.

[zac510]

This is a more general question, but is there an aerodynamic reason why a car might lose it's rotational inertia and get 'stuck' at 90degrees yaw?

Although thinking about this now it could be the driver's foot on the brake that is stopping the car from continually rotating.

[Tim the Grey]

I guess there must be, as it does seem to happen that cars get sideways, and then seem to stay there... Look at Pug 7 video as yet another example?

[AU N EGL]

Originally Posted by zac510

This is a more general question, but is there an aerodynamic reason why a car might lose it's rotational inertia and get 'stuck' at 90degrees yaw?

Although thinking about this now it could be the driver's foot on the brake that is stopping the car from continually rotating.

driver tried over correct and held the steering wheel in place. When the car comes around, the driver should have let the steering wheel go so the car will wind up going backwards, then grab the streering wheel and both feet in. brakes and clutch.

that 'stuck' at 90degrees was most likely driver error. YES even profressional race drivers mess up once in a while

[Mal]

Originally Posted by JAG

The increase in speeds over the last few years is almost entirely down to increased cornering speeds, acceleration/braking is very similar between a 908 and any P1 from the last 10 years. .

I don't agree it is the accelaration through the torque of the diesel engine that has made the biggest difference in lap times - you just have to look at how the Audi can overtake 2 or 3 rows of cars in the ALMS restarts to see the effect that has had.

[prototype]

Lola Mazda just flipped multiple times after spinning. Once the car got sideways at speed it went airborne.

[JAG]

The thing is, it wasn't going that quick, and coming into the braking area.

You'd struggle to make a car take off that easily if you designed it specifically!

And once again, it takes off, then flys relatively low, not uncontrolled like the old GT1 flips.

[Stefvh]

How many cars, now, with the same airborne ?