Inclining the car as the steering wheel is turned?

[g-force_addict]

To counteract body roll
Would an entirely mechanical suspension that inclines the car as the steering wheel is turned, be allowed by the rules?
For both front and rear suspension.

[Tim.Wright]

Whats wrong with body roll?

[Lycoming]

why not just make your roll center as high as your center of gravity?

[MadMatt]

Whats wrong with body roll?

As you are not an engineer in a F1 team, you must not be aware that attitude change upsets flow under the car (especially diffuser), isn't it?

I think the Mercedes Carving concept was quite interesting:



If you want to move the whole car then active suspension.

[Tim.Wright]

In my opinion roll control is massively overrated mainly by observers and consumers who equate low roll = better handling. From a suspension point of view, stiff roll modes are used to deal with bad kinematics and themselves increase the warp stiffness of the suspension which kills grip. From an aero point of view, I think pitch (mainly of the front axle) is a much more critical mode to control (and in fact, there is a signficant effort in F1 now in this direction).

Such a system to counterract body roll by effectively offsetting the spring movement by a steering imposed movement may show a small improvements in aero but at significant cost in terms of weight. Anything which is moving the roll angle in this manner, will be fighting against the wheel loads which are in the range of 100's of kilos. The power steering system could be improved to deal with these loads but the result will be tha the system is illegal because its running off the power steering system.

If you try to make it passive, the driver wont be able to turn the steering wheel.

For road cars, Mercedes already have such a system in production. Called active body control I think.

P.S. The carving had nothing to do with roll control. It was a study into the effects of actively changing the wheel camber angles.

[DaveW]

Whats wrong with body roll?

Not a lot, but it does introduce a time delay into steering inputs (which most drivers would prefer to be without). Body roll is necessary if the car doesn't have a natural lateral balance (in order to cross weight the car in a turn).

why not just make your roll center as high as your center of gravity?

Because drivers tend to object to the "feeling" of the car as it "tries to climb over" the loaded wheels.

If you try to make it passive, the driver wont be able to turn the steering wheel.

Apologies, I don't understand the statement, Tim, although it is true that the geometry might have to be modified....

In our active F1 project (manually steered Lotus T99) the suspension was designed to roll the car slightly inward to counteract tyre defections. Otherwise, no roll was the preferred solution, even in a road car. Lack of roll transient dynamics was very apparent.

[PlatinumZealot]

To counteract body roll
Would an entirely mechanical suspension that inclines the car as the steering wheel is turned, be allowed by the rules?
For both front and rear suspension.

Check my thread here:

A new way to drive an F1 car? "3D driving"
http://www.f1technical.net/forum/viewto ... 3d+driving

Very interesting concept and I think it has good promise. I am pretty glad someone else thought of something in a similar vein.

[Tim.Wright]

Whats wrong with body roll?

Not a lot, but it does introduce a time delay into steering inputs (which most drivers would prefer to be without). Body roll is necessary if the car doesn't have a natural lateral balance (in order to cross weight the car in a turn).

The race car's I've dealt with deliberatly took out bumpsteer and lateral compliance steer from the suspensions in order to reduce any roll induced changes to the vehicle trim. I also suspect (still an open point in my mind) that drivers use body roll as a feedback cue. If you take this away (or try to compensate for it with a system that has a different phase response to what the body is trying to do), it could have a subjectively negative effect on the driver's ability to feel the car. I might be wrong though. I'm sure you would have some useful subjective feedback from the Lotus which could further the discussion.

why not just make your roll center as high as your center of gravity?

Because drivers tend to object to the "feeling" of the car as it "tries to climb over" the loaded wheels.

The body will probably end up rolling into the turn center in this case. Traditional roll centres are no good at predicting roll movement outside of low lateral accelerations. Having roll centres so high will also give you significant jacking of the chassis which will end up ruining the aero anyway. I suspect there would be significant transient handling disadvantages to having roll centres so high as well.

If you try to make it passive, the driver wont be able to turn the steering wheel.

Apologies, I don't understand the statement, Tim, although it is true that the geometry might have to be modified....

In our active F1 project (manually steered Lotus T99) the suspension was designed to roll the car slightly inward to counteract tyre defections. Otherwise, no roll was the preferred solution, even in a road car. Lack of roll transient dynamics was very apparent.

I figured trying to force a 600kg chassis with a roll inertia of say 2-300kgm²to follow stering inputs would involve significantly large forces.

Out of interest, how did you acheive this steer induced roll? Why was this necessary given the system was active?

[Tim.Wright]

To counteract body roll
Would an entirely mechanical suspension that inclines the car as the steering wheel is turned, be allowed by the rules?
For both front and rear suspension.

Check my thread here:

A new way to drive an F1 car? "3D driving"
http://www.f1technical.net/forum/viewto ... 3d+driving

Very interesting concept and I think it has good promise. I am pretty glad someone else thought of something in a similar vein.

If I remember correctly, the conclusion of that thread was, short of punching the driver in the throat each time he drives past, there is nothing else on the market that would simultaneously slow the car down and inconvenience the driver to the same degree as 3D driving would...

[DaveW]

I also suspect (still an open point in my mind) that drivers use body roll as a feedback cue. If you take this away (or try to compensate for it with a system that has a different phase response to what the body is trying to do), it could have a subjectively negative effect on the driver's ability to feel the car.

We worried about that too, but it turned not to be a problem - quite the reverse, actually.

The lotus active suspension system used "irreversible" hydraulic actuators on each corner driven by velocity demands based on measured loads. Load cell readings were converted to "modal" loads and corrected for deterministic components that were measured but not wanted, so longitudinal acceleration was used to correct pitch measurements, lateral acceleration was used to correct roll measurements, airspeed was used to compute & correct heave & pitch measurements (the idea was to use pressure measurements for that, but we were never successful), etc. A few other unwanted components were removed (e.g. change of vertical suspension loads with steer). The corrected loads were used to produce desired model velocities, which were converted back to corner velocities and used to drive the actuators. A few other refinements were required to maintain lateral balance, level the suspension, limit suspension travel, control the hub modes, etc.

The system was parameter based and, in a two seat prototype, the parameters could be controlled on the move. For everyone I think, the prototypes were fantastic learning tools. The F1 version included a switched potentiometer that could be used to control any (single) parameter.

Anyway, being able to control roll angle per gn quickly taught us that roll is not required to control the car. In fact roll out or roll in caused transient body motion that can interfere with driver cues. Best was to have none at all - as any kart driver will tell you, I guess. We used slight roll in for F1 to keep the platform flat with the ground (i.e. compensating for tyre deflection), but my memory recalls that it was not very sensitive.

You asked about steer induced roll, I hope that the summary above will tell you it was not used, as such, but steer position was used as a "trajectory demand" to balance the vehicle, and to correct (in some cases) vertical loads due to steer.

I hope this helps.

[Tim.Wright]

Yea sweet thanks.

[PlatinumZealot]

To counteract body roll
Would an entirely mechanical suspension that inclines the car as the steering wheel is turned, be allowed by the rules?
For both front and rear suspension.

Check my thread here:

A new way to drive an F1 car? "3D driving"
http://www.f1technical.net/forum/viewto ... 3d+driving

Very interesting concept and I think it has good promise. I am pretty glad someone else thought of something in a similar vein.

If I remember correctly, the conclusion of that thread was, short of punching the driver in the throat each time he drives past, there is nothing else on the market that would simultaneously slow the car down and inconvenience the driver to the same degree as 3D driving would...

3D driving would be designed to be additive to the dynamics. ie make it faster.

[Anthonyjura]

Yeah i saw that tree once when i hit "last active" its really awesome how you are using the circle tool to create the leaves its epic