Will 4 wheel steering make it's way into F1?

[Conceptual]

The rear tires already steer into the turn, every bit as much as the fronts. The difference is, whereas the fronts are steered by driver input.. the rears are steered by the chassis yawing.

In a road vehicle on turn entry you WANT only the fronts to steer. Momentarily when you move the steering angle the fronts are the only tires developing lateral force and thus develop a yaw acceleration which starts the car actually turning. Once the chassis yaws a bit that steers the rear tires, the yaw moment goes away but the car is still rotating, and is now cornering.

On a neutral car, mid corner at max capacity the front AND rear tires are already steered to their max/optimum point. Having additional steering would do nothing. If your car was understeer and the rears had excess grip capacity yea you could technically steer them some more but that will just make the car plow. I'd imagine it would make the car understeer more.. you'd get a bit more lateral acceleration very briefly and then the car would start to yaw OUT of the turn! Not very good for getting the car pointing down a straight.

4WS is good for a low speed or stationary application when you want something that can turn on basically 0 radius (like a forklift) or move purely laterally without really "turning" the car (ultimate for parallel parking!).

But there's no reason for it on a good racecar.

If the 4 tyres are already steering in a corner, then why do alot of the F1 drivers still drift a bit? Wouldn't 4WS effectively give you the same line as the drift, but still allow the application of power? And in your response about the reverse yawing of the chassis, is that not caused by steering correction more than wheel vector?

Thanks!

Chris

[Ciro Pabón]

AFAIK, many rear wheels steer "passively" because they're designed to do so. They have to have Watt linkages or toe control bushings. If they weren't designed like that, like in very old cars, you would have countersteering in the rear wheels, because they "toe out" in a curve.

4WS has two different applications: for slow cars (rear wheel countersteer) or faster cars (rear wheels steer in the same direction).

For large cars, the first option (rear wheel countersteering) is very good for diminishing turn radius.

With the second option (same direction steer), unless you want your car to move like a crab, for, I don't know, changing lanes, the amount of "same direction steering" you can give to rear wheels is slight, thus, the amount of vectoring you can give to the acceleration is slight.

I don't know if Jersey Tom refers to the first or the second kind of steering in his description of a 4WS car turning behaviour.

There is a really curious wheel used only in forklifts (AFAIK) with this kind of wheel that allows you to move laterally:



Airtrax site (with videos of forklifts moving diagonally)

I've already posted the previous picture in the spherical wheels thread.

In that thread I theorized (without much success) that a fully steerable rear axle would allow you to "thrust" the car into the curve, the same way a rocket or a Harrier jet steers by steering the impulse of its engines.

[RacingManiac]

4WS might help in transient condition though, to help the rear reach peak lateral grip faster. Most modern 4WS system on passenger car does both mode anyway. Low speed they counter steer and high speed they parallel steer.....

[Jersey Tom]

Chris/Conceptualist-

Can't say I remember seeing an F1 car in any sort of "drift" (ie a trimmed oversteer condition). Do you mean, why is there power-on oversteer?

A tire can only generate so much force in any direction. Once you demand enough drive thrust from it and it saturates the thing, demanding any more reduces lateral grip capacity. No amount of extra rear wheel steering will get more out of it once that extra drive torque gets applied. When that happens, you once again go back to the unbalanced yaw moment condition where the rears are no longer producing a trimming effect, and the car over-rotates (oversteers/spins) momentarily until the driver corrects for it.

Not sure if I understand your second question. Steering correction IS the wheel vector, at least on the fronts. Direct link. My comment earlier was in response to yours that understeer would go away. Limit understeer means that the front tires have saturated their lateral grip capacity before the rears. The rears are in excess and aren't being used. In addition, since the fronts are soaked you can't rotate the car and steer the rear tires any more to get more lateral force out of them. But even if you COULD steer the rears extra by using 4WS it does you no good. You get extra lateral force momentarily but the car is no longer balanced then, and the reverse yaw moment would just rotate the car away from the turn.

Remember.. high speeds and actual vehicle handling is all about forces and moments, not necessarily how to get the wheels pointed where they would want to go in a purely geometric sense.

And yea, technically you could get the rear end to hook up faster with 4WS on a "taily", shitty car. But the yaw and cornering response times for an F1 car are so outrageously quick as it is the gain would be imperceptible.

[Conceptual]

Chris/Conceptualist-

Can't say I remember seeing an F1 car in any sort of "drift" (ie a trimmed oversteer condition). Do you mean, why is there power-on oversteer?

A tire can only generate so much force in any direction. Once you demand enough drive thrust from it and it saturates the thing, demanding any more reduces lateral grip capacity. No amount of extra rear wheel steering will get more out of it once that extra drive torque gets applied. When that happens, you once again go back to the unbalanced yaw moment condition where the rears are no longer producing a trimming effect, and the car over-rotates (oversteers/spins) momentarily until the driver corrects for it.

Not sure if I understand your second question. Steering correction IS the wheel vector, at least on the fronts. Direct link. My comment earlier was in response to yours that understeer would go away. Limit understeer means that the front tires have saturated their lateral grip capacity before the rears. The rears are in excess and aren't being used. In addition, since the fronts are soaked you can't rotate the car and steer the rear tires any more to get more lateral force out of them. But even if you COULD steer the rears extra by using 4WS it does you no good. You get extra lateral force momentarily but the car is no longer balanced then, and the reverse yaw moment would just rotate the car away from the turn.

Remember.. high speeds and actual vehicle handling is all about forces and moments, not necessarily how to get the wheels pointed where they would want to go in a purely geometric sense.

And yea, technically you could get the rear end to hook up faster with 4WS on a "taily", shitty car. But the yaw and cornering response times for an F1 car are so outrageously quick as it is the gain would be imperceptible.

Maybe a Lemans Proto then?

For some reason what I have read about the different systems leads me to believe that the major problems that have been encountered stem from the fact that while the wheels may have 4 wheel fully independant suspension, they do NOT have individually controllable drive, so across the car, there are % splits of power that are interconnected. I think that is what causes these issues.

ANd Jersey Tom, I understand about your tyre saturation, but my response to your claim about the tyre saturation is that if the 4 wheels are independantly driven, and not dependant on a power split %, that you not only could keep them perfectly balanced by being able to quickly shift weight, but you could also have bursts during the transiense of shifting and steering. Your "moments" are a continual series of events where the hard coded algorythm of the power split, thus not operating the 4 wheels independantly. I am saying that those "moments" happen continuously through a corner, and independent power to the wheels can maximise the contact patch for whatever vector it is in, and it wont get short-changed because its % of available power is too low.

I respect your information, and your willingness to share it. I have thought about it alot, and I appreciate where my understanding is now as compared to before. Thank you for your help.

Chris

[Jersey Tom]

Oh certainly. Drive torque distribution is huge. Audi proved that when they entered pro rally with Quattro. Blew people away. An AWD system for an F1 car would be nuts.. hell I'd love to see Audi come in with an F1 Quattro car

But that's 4-wheel drive rather than 4-wheel steering..

[Scotracer]

I'm not sure how much of an advantage 4WD would be in F1. The cars only seem to be breaking traction at very low speeds for a very small portion of the lap...the downforce quickly sorts traction out. Contrast this with rallying where traction is at a premium on the loose surface, with no downforce.

Personally, I think 4WD would be detrimental to the sport as there would be more transmissional losses but again, if it's introduced with KERS that would be nullified.

What I'm worried about next year is the extreme grip the slicks will provide...will the lack of TCS be moot?

[WhiteBlue]

If a 4WD system is allowed it may be all electric and the ICE only used to charge the batteries. the noise lovers would really hate this I guess.

[Jersey Tom]

That initial traction out of slow corners is very important though.

Slicks will give an increase in grip, but it won't be a crazy amount. You'll still be able to break the rear end free without too much difficulty I'd imagine.

[Scotracer]

If a 4WD system is allowed it may be all electric and the ICE only used to charge the batteries. the noise lovers would really hate this I guess.

Yep...

The FIA has actually said they want to keep the noise levels similar. One justification from Mosley for the V8s was that "they sound nice"...so it must hold some value. For instance, tonight I was at a Heavy Metal concert (Children of Bodom for anyone into that genre) and if they had decided to turn down the noise level to save electricity...well, it wouldn't be half the show it was. Noise is important!!!!!

That initial traction out of slow corners is very important though.

Slicks will give an increase in grip, but it won't be a crazy amount. You'll still be able to break the rear end free without too much difficulty I'd imagine.

Perhaps. Possibly, with the reduction in downforce we may see the same longitudinal traction.

[Hawkeye]

The 1993 Benetton did race with 4 wheel steering, at the last two races, Suzuka and Adelaide. On Schumacher's car it was worth 3 tenths per lap, but Patrese didn't like how it felt and so used to race with it switched off...There's a cool article in Racecar engineering from November 2002 Vol 12 No.11, where Pat Symonds talks about it.

[Hawkeye]

A few quotes from the article, for those who are intersted. Pat Symonds: "The handling benefit of the active system was control of roll stiffness distribution, which of course is reasonably powerful at low speed, but not incredibly powerful at high speed. The four wheel steer gave us a primary control - steering the rear wheels does move the car around a bit!.
"The perceived gain was that we would have a very powerful first order handling control which could be very specific in that we could tune it corner to corner because for any lap there will be come reasonably defined points on a speed versus steer angle chart. We felt we could provide an individual handling control for each corner, and thats pretty well how it turned out.
"We used distance mapping at Suzuka through the snake section behind the pits, because that last bend there is real understeer. We used to kick the rear wheels like hell through there. We could also counter steer initially so as the car came up to say a right hand corner, the rear wheels would turn left to throw the car into the corner".

[RacingManiac]

that must feel rather awkward from the driver's point of view....especially if what I read was correct it is setup from point to point of a track so it's kinda like a rollercoaster....

[Hawkeye]

Symonds: "It's probably true that we never got more than 70% of the benefit out of it. It was very much a driver feel thing, and we just didn't have enough track time to give th drivers confidence in it and to get the optimum time out of it."