Variable Camber

[Belatti]

... But i insist, there is no need to put on heavy equipment, like servos or pushrods, in a car to achieve camber change. It can be done passively with the geometry of the suspension.

Can you tell us how?

If you dont wanna tell us here, I would pay you thousands of dollars if you can design for me a car with your passively suspension geometry that can have 0° camber in the straights and, while rolling, controlled negative camber in the outer wheels and controlled positive camber in the inner wheels.

http://scarbsf1.com/renault_opt/Renault_OPT.htm

Dave, check my post from Tue May 05, 2009 1:34 pm

As I have said, al_kar got a point and right now Im on it.

[RacingManiac]

has there been any further development to this though? It seems that in an era where the mechanical grip is more important something like this could be helpful, if it works.....especially kinematically speaking this should be less complicated than something like Inerter....

though it has to be noted, Bridgestone won't develop tires for it...

[al_kar]

There is a very simpler solution to change the camber in corner. I race r/c cars for over 4 years and with the last car, that i bought 2 years ago (XRAY NT1), i've raced about 15 races. this is a picture of the back suspension. the suspension keeps a certain camber in the strait but in the corner the outer wheel develops a more negative camber and the inner a more positive because of the roll of the body of the car.

[Carlos]

Here is a 5 link suspension that performs similarly to the Renault OPT system. Click & enlarge the wheel/suspension diagrams to see the suspension in motion.

http://www.madabout-kitcars.com/kitcar/kb.php?aid=375

[safeaschuck]

Am I missing it? What does OPT do that unequal length double wishbones don't?
It MUST be something otherwise surely Michelin wouldn't have gone to all that trouble? Help!

[Giblet]

Won't unequal length wishbones only have one situation where the car sitting on it's optimal contact patch?

I see it as if the camber is in any way "permanently set" through the actual geometry of the suspension, there will be a shortcoming in the contact patch (or more specifically the tire being perpendicular to the road) either in the straight, or on one side.

Is this right? The linkage allows for perfect camber on the straights, and on both sides in the corners?

[Jersey Tom]

Ehhh...

Not really sure what you mean by "only one situation on its optimal contact patch."

The Renault thing doesn't make a magical suspension. It's just a more complex linkage. Might it work better in some applications? Sure. All of them? Not necessarily. There are for example times when the unladen inside tire doesn't really care what inclination angle it's at.. in which case you can focus on the outsides and a standard SLA suspension works great.

Additionally there are "real world" factors to take into consideration. Compliance is a big one. Compliance can really murder your grip level. Adding that many more pivot points and joints... there's got to be an impact.

[Conceptual]

Ehhh...

Not really sure what you mean by "only one situation on its optimal contact patch."

The Renault thing doesn't make a magical suspension. It's just a more complex linkage. Might it work better in some applications? Sure. All of them? Not necessarily. There are for example times when the unladen inside tire doesn't really care what inclination angle it's at.. in which case you can focus on the outsides and a standard SLA suspension works great.

Additionally there are "real world" factors to take into consideration. Compliance is a big one. Compliance can really murder your grip level. Adding that many more pivot points and joints... there's got to be an impact.

I really haven't worked out a model for this yet, but for some reason, the OPT system looks redundant for some reason. I will try to chase down what my subconscious is telling me, and post if it amounts to anything.

Killer stuff tho. In the age of low aero, mechanical grip, especially with slicks would seem like a huge advantage. Could implementing a type of this suspension cure the front/rear tyre issues that the teams are currently having? I think that would be better than narrow front tyres for next year...

Can someone explain to me why the current Bridgestones would NOT benefit from a suspension that keeps the tyre perpindicular? Are they designed to be abused on the inside edge, and frail on the outside one? I really don't see how maintaining an optimum contact patch could NOT work with a certain tyre.

I appreciate any explaination!

[Jersey Tom]

I wouldn't call this the age of "low" aero. It is lower than it had been, but still massively prevalent. The age of LOW aero was late 60s and early 70s.

Would it cure front/rear balance problems? Doubtful. Why would it?

If you keep the tire perpendicular to the pavement you are throwing away massive amounts of grip and will be MORE abusive than if you can incline it. And I just really don't like the phrase "optimum contact patch." Sounds so hokey.. and it doesn't really exist.

[mike]

opt reacts to the displacement in the suspension, but the oncamber/F400 system doesnt, it reacts to the input of the driver
i can see that OPT will not work properly in bump situations as it definately have bump camber
the oncamber/F400 only reacts if you turn the wheel of the car and not the during bumping. so depending on the steering wheel input/camber out put, you should have perfect setting for most of the corners on a track, depending on the input of the steering wheel from a particular driver and the camber you want for each corner.

[Belatti]

the suspension keeps a certain camber in the strait but in the corner the inner wheel develops a more negative camber and the outer a more positive because of the roll of the body of the car.

al_kar, we want the opposite to occurr!

Think about what you are saying, that is what normally happens and is what we want to change.

There are for example times when the unladen inside tire doesn't really care what inclination angle it's at.. in which case you can focus on the outsides and a standard SLA suspension works great.

Additionally there are "real world" factors to take into consideration. Compliance is a big one. Compliance can really murder your grip level. Adding that many more pivot points and joints... there's got to be an impact.

First you say white, then you say black. Pick a side!

Of course the unladen inside tire cares, every single bit of grip counts. If you focus on the outsides you have to chose between 0° camber in straights for more linear grip and negative in corners for more lateral grip. A standard SLA suspension works great but its what everybody has and we are talking about something grater here, arent we?

I will try to model something in a suspension software if I can. The one I know has standard parts so it wont be easy to model if not impossible. Otherwise a shot with Autocad 3D can be a good exercise.

[Jersey Tom]

There are for example times when the unladen inside tire doesn't really care what inclination angle it's at.. in which case you can focus on the outsides and a standard SLA suspension works great.

Additionally there are "real world" factors to take into consideration. Compliance is a big one. Compliance can really murder your grip level. Adding that many more pivot points and joints... there's got to be an impact.

First you say white, then you say black. Pick a side!

Of course the unladen inside tire cares, every single bit of grip counts. If you focus on the outsides you have to chose between 0° camber in straights for more linear grip and negative in corners for more lateral grip. A standard SLA suspension works great but its what everybody has and we are talking about something grater here, arent we?

I will try to model something in a suspension software if I can. The one I know has standard parts so it wont be easy to model if not impossible. Otherwise a shot with Autocad 3D can be a good exercise.

I believe first I said black, then I said black. I'll clarify. My first point is there are times when (in terms of lateral force) the unladen tire DOESN'T care what inclination angle it's at, within any discernible quantity. There's gray area there.

Second point is that with this more complex linkage you're inevitably adding joints and members. That is probably going to introduce extra compliance. Compliance might kill off way more grip than would be gained in a perfect world if everything were infinitely rigid. Plus, it likely adds weight.

Yes, everyone has a SLA suspension. There's a reason for that. I believe one of the links earlier even pointed out Renault tested this a few years back, in F1.. promptly dropping it? We're not necessarily talking about something "greater," by any means. It's different, is the only thing we can confidently say. May be better, may be worse. It's certainly not new. Renault is sending out pamphlets about this thing, had one on my desk at work a year ago or something.

Furthermore, it's not ALWAYS about "maximum grip" independently at each corner. Things aren't quite that one-dimensional.

[Belatti]

I believe first I said black, then I said black. I'll clarify. My first point is there are times when (in terms of lateral force) the unladen tire DOESN'T care what inclination angle it's at, within any discernible quantity. There's gray area there.

You mean when managing WT you made one axle transfer all of its weight and the inner wheel is almost in the air?

Second point is that with this more complex linkage you're inevitably adding joints and members. That is probably going to introduce extra compliance. Compliance might kill off way more grip than would be gained in a perfect world if everything were infinitely rigid. Plus, it likely adds weight.

Yes, everyone has a SLA suspension. There's a reason for that. I believe one of the links earlier even pointed out Renault tested this a few years back, in F1.. promptly dropping it? We're not necessarily talking about something "greater," by any means. It's different, is the only thing we can confidently say. May be better, may be worse. It's certainly not new. Renault is sending out pamphlets about this thing, had one on my desk at work a year ago or something.

OK, maybe it was not good for the F1 level. I work with stock cars so Im thinking about doing something there. Stock cars hubs weight a lot and I think compliance problems wont be a headache there. I was talking about "greater" because it was the word that came to my mind when I thought about something better.

Last month I went to a junior tourism car silhouette series (Top Race Junior):



These cars are rev limited and have fixed gearbox ratios to control costs. I was standing at the final of the main straight and one particular car hitted the rev limiter 100m before the others in 5th gear. When I said: "Wow, that driver knows how to manage traction out of the hairpin entering the main straight" as all the cars are equal. Then a race engineer told me that car was aligned in such a way it has better traction but would be lousy turning. I asked: "whys that?". He replied me: "because the driver is a 17 y.o. kid that still does not push to the limit in the corners, he doesnt know the track and has got no experience, but anyone can push hard in a straight..."

I bet that car had less camber in the rear wheels. After that I have been thinking in a suspension geometry that can minimize camber changes, till this thread showed up.

Furthermore, it's not ALWAYS about "maximum grip" independently at each corner. Things aren't quite that one-dimensional.

Could you be more specific, please?

[Jersey Tom]

You mean when managing WT you made one axle transfer all of its weight and the inner wheel is almost in the air?

Nah, not quite. Obviously if the tire is dangling it really makes no difference. But with certain tires, at certain inflation pressures, you can have a somewhat light but non-zero load and the camber doesn't really do anything for peak grip. Other times it may be a big deal.

OK, maybe it was not good for the F1 level. I work with stock cars so Im thinking about doing something there. Stock cars hubs weight a lot and I think compliance problems wont be a headache there. I was talking about "greater" because it was the word that came to my mind when I thought about something better.

I also work with stock cars (in the US). They're heavy, but that doesn't necessarily mean they're rigid. Compliance rates can be very surprising.

Furthermore, it's not ALWAYS about "maximum grip" independently at each corner. Things aren't quite that one-dimensional.

Could you be more specific, please?

There's a lot to consider... slip angle drag, aligning torque effect on balance, overturning moment effect on corner loads, durability and wear, weight jacking, aligning where the left and right tires peak for force, controlling ultimate vehicle sideslip angle for aero, rolling resistance, cornering stiffness load sensitivity, steering sensitivity progressiveness, combined drive/brake/cornering effects, loaded radius for controlling splitter, wing and diffuser heights, yatta yatta.

Pure peak lateral force is only a small part of the puzzle.

Does the trick Renault suspension have some potential? Sure. Don't get me wrong, it might be something that could be made to work very well in the right application. As if good suspension design weren't involved enough, this adds a substantial element of complexity. To really exploit it I believe you'd need accurate tire data, excellent kinematic software, and/or extensive use of a K&C rig.

[Belatti]

Thanks Tom!

To really exploit it I believe you'd need accurate tire data, excellent kinematic software, and/or extensive use of a K&C rig.

Tire data is a miss here. Sadly that happens in all "control tire" series. Even I quited my intents to get "home made" tests for data: our tire manufacturer doesnt have repeatability and reproducibility in its process.

The kinematic software is something I guess I can have.

The K&C rig, I have heard it costs at least a million.