steering

[wrk]

i first noticed this on the clip of MS in qually at monaco then paid attantion to it in last nights race , but does the out side wheel seem to turn in sharper than the inside wheel either turning left or right....or is it just the fish eye lense that is on the onboard cam???

[West]

Well the Milliken brothers state in their Race Car Vehicle Dynamics book that that is the proper way to set up steering, which may be against most people's view of Ackermann steering.

[tpe]

I had see that to other cars too. I do not know if it is a Monaco only solution, but definately other cars had it too (sorry, I do not remeber which ones). I will search at the regulation in order to see if that is allowed, though.

[RacingManiac]

Well the Milliken brothers state in their Race Car Vehicle Dynamics book that that is the proper way to set up steering, which may be against most people's view of Ackermann steering.

Milliken Father and Son...... Bill is the dad, Doug is the son....

I think what's seen on TV is more of a perspective thing. Though anti-ackermann is used in F1, I don't know if Monaco is the track they'll use it. With the speed being slow the load transfer on the car will probably not necessitate the anti-ackerman, and with the super tight corner of the track the excessive inside wheel scrub will probably be undesirable.

To recap, ackermann regularly, is used so that inside turns more than the outside, due to difference in turn radius travelled by the wheels on either side. Anti-ackermann, or reverse-ackermann as said by others, is when you do the opposite. The reason you would use the latter is because on some tire(not necessarily all tires, depends on tire data), the peak lateral force happens at higher slip angle as load increases, and thus to maximize the use of tire, since the outside tire is more heavily loaded at speed, you need to give it more slipangle vs the inside which is at a lower load.

[MrT]

No, many of the teams were indeed running anti-ackerman. This tends to give good results in slow speed tight corners, like those found at monaco. It is also often implemented to help heat the front tyres. It was definetly not just a TV perspective thing.

[Jersey Tom]

I'm not so sure Reverse Ackermann would do much to heat you front tires. You might think it would scrub the tire accross the track, but it shouldn't. The tire is still gripping and sticking to the road rather than sliding. Running aggressive Pro-Ackermann though, driving an unloaded inside tire to too high of a slip angle would probably start it sliding and scrubbing accross the track. I've tried this on some extremely soft slicks but it just pushes the rubber off the tire and wears it very quickly. I'd much rather run reverse. Then again I don't have a ton of downforce.

But yea, Reverse Ackermann is much more beneficial in low-speed, high-G turns. At high speed you still have the weight transfer but the steered angle is much smaller and so is the difference in slip angle left to right. Low speed with a very high steered angle you just can't drive that inside tire to as high a SA.

Then again, as was mentioned, its all a matter of tire data. All the race tires I've seen though are biased towards reverse ackermann under high-G loading.

[RacingManiac]

This does give me something to think about....gonna have to test that setting on the car next time out.....

[Ciro Pabón]

It is totally Ackerman:



After all, the steering angle at Monaco is twice the angle at any other race. Besides, the radius of this corner and the speed are really low. I estimate the radius to be less than 20 meters. The steering angle of the left wheel is probably over 35 degrees.

[Jersey Tom]

What kind of car do you have, Maniac? Its not the easiest adjustment, unless you can move your rack forward and back a couple feet or have some sort of adjustment in the relation between your upright lower balljoint and steering pickup.

And what kind of cornering forces and weight transfer are you seeing / expect to see? I'd love to hear how it works out. The most we pull is 1.7G without any aero system.

[RacingManiac]

same kind of car you have;)

We have outboard ackermann adjustment by varying the outboard steering pickup location in relation to steering axis. We have so far done parallel and positive in our ontrack testing and have found positive actually works alright(+50%), better the parallel anyhow. So we didn't bother to go the other way despite we do have that setting.

I am from University of Toronto BTW...

[flynfrog]

Im from the Iowa State fsae team

[marcush.]

anti ackerman is really a functiobn of the tyre characteristic.
It caters for the load sensitivity of the tyre .This load sensivity dictates that in terms of F1 nowadays you need less Slip angle on the inner (less loaded) wheel to get a bit more grip.
If this is true for a different tyre and for your specific car is debatable.First of all you need to make sure the inner tyre contributes as much as possible carrying load in a corner,and to have it as flat as possible on the track doing this (think of camber gain /loss in steering action ).
a tyre in the air can have whatever camber or toe setting ....with no effect at all.

[Jersey Tom]

Indeed. Which is why its nice to have slip angle vs cornering force and self-aligning torque plots

[marcush.]

I don´t belive in paper....I think intelligent testing supplies the data and real world data.
Of course then you´ve got to go to the drawing board(err CAD) and create the necessary geometries to maximise your findings.very rarely the beast you are working with has a range of adjustability to suit all your needs simply turning wrenches ....but that´s why some guys have better cars...

[MrT]

I'm not so sure Reverse Ackermann would do much to heat you front tires. You might think it would scrub the tire accross the track, but it shouldn't. The tire is still gripping and sticking to the road rather than sliding. Running aggressive Pro-Ackermann though, driving an unloaded inside tire to too high of a slip angle would probably start it sliding and scrubbing accross the track. I've tried this on some extremely soft slicks but it just pushes the rubber off the tire and wears it very quickly. I'd much rather run reverse. Then again I don't have a ton of downforce.

But yea, Reverse Ackermann is much more beneficial in low-speed, high-G turns. At high speed you still have the weight transfer but the steered angle is much smaller and so is the difference in slip angle left to right. Low speed with a very high steered angle you just can't drive that inside tire to as high a SA.

Then again, as was mentioned, its all a matter of tire data. All the race tires I've seen though are biased towards reverse ackermann under high-G loading.

It has been found that there are heating effects, as more tyre distorsion is created (not scrubbing, but tyre slip angle!) This greater distorsion puts more energy into the tyre, and hence produces some heating effect.