I noticed that inside front tyre will often heat up on entry. That makes sense as there's lower loads and the wheel tends to lock up because of trail braking. However in the Monaco FP3 I noticed on Riccardo thermal cam that the inside front wheel heat up momentarily arond the apex in the tunnel section, where they are flat out and don't apply any brakes. The outer wheel was cold, which hints that the lateral forces are not that high in the tunnel.
So what caused the inside tyre to lit up?
Did he just hit the kerb slightly or there's a patch of especially abrasive pavement somewhere in the apex?
Tim.Wright wrote:Perhaps the left tyre was on a white line which offer little grip, so for a moment the inside (right) wheel was carrying most of the cornering force
Interesting, so it's basically an understeer moment?
What I described would be an understeer instant but after watching qualy, the travelling over the white lines is happening too quickly for it to cause a change in temp.
Rikhart wrote:It was mentioned on Sky that happened because of the camber of the wheel.
First thing's first.. don't pay attention to what the TV announcers say
Though there's a fair point to be made that running negative camber, going into a corner, rolling and unloading the inside front tire - it will be sitting on a very small footprint area. Could see that raising surface temperature on a small band of rubber.
There's also toe to be taken into account. And Ackermann. And surface emissivity and how that changes. Quality of camera. Scaling of data. Etc etc.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.
Rikhart wrote:It was mentioned on Sky that happened because of the camber of the wheel.
First thing's first.. don't pay attention to what the TV announcers say
Though there's a fair point to be made that running negative camber, going into a corner, rolling and unloading the inside front tire - it will be sitting on a very small footprint area. Could see that raising surface temperature on a small band of rubber.
There's also toe to be taken into account. And Ackermann. And surface emissivity and how that changes. Quality of camera. Scaling of data. Etc etc.
Imagination of data scraper...
The car is very stiff in Torsion so corner weights shift not just because of dynamic wheel Transfer of cornering breaking and acceleration but also as the road Ondulations get covered by the car .it may well be the reason why a sudden move of cornerweights may rise tyre temps quite quickly on the wrong tyre ?
lots of toe out. which IMO helps (or is perceived to help) in turn-in and especially for slower corners, but on higher speed sweepers steers the inside wheel more than geometrically necessary. i'd note that this also helps heat the tire, which all were having problems with.
thisisatest wrote:lots of toe out. which IMO helps (or is perceived to help) in turn-in and especially for slower corners, but on higher speed sweepers steers the inside wheel more than geometrically necessary. i'd note that this also helps heat the tire, which all were having problems with.
no-this would Show as rising temp as you go in a straight line -which is not the case in the motionpictures i have seen
it`s simply lots of camber and the shift of crossweights due to road surface twist which causes these counterintuitive rises of temps on the wrong side of the car.
a Minute Change in static toe will not really influence mid corner temperature of the inside wheel ..this is not ackerman really pointing the inside wheel in a specificly different Position which cause dynamic toe what you were not talking about ?:
ackerman does create dynamic toe, of course. but do they run ackerman or anti- or neither right now? i thought the theories have come and gone.
the camber certainly explains why the heat is on the inside edges (and more across the tread on the outside tire).
what do you mean by road surface twist? if you mean the "corkscrew" effect on the tight descending bends, i'd have to disagree as that unweights the inner front more. as an example, Lewis' car going through there had his inside front locked up mid corner but zero flat spot afterwards.
it is also my belief that they run quite a bit more than a "minute" amount of toe out.
...and the second picture is an optical illusion caused by the camera position and field of vision. direct overhead shots show they run static toe out.
I heard they don't follow ackermann strictly even in roadcars these days. If it is road camber, you have to see what happens in those ovals in INDY. Camber seems to be the only possible explanation. Also is it only on the redbull or in all cars?. we have to wait till silverstone for another such sweeping corner.
I've done a few calcs and I'm sure its the static toe...
Whats happening is that the lateral acceleration is so low that the slip angles at the tyres that are required to do the corner are about the same as the slip angle imposed by the static toe setting. This results in the inside wheel having a slip angle about double of the static toe value and the outside wheel has zero slip, so is generating no heat.
Here is my justification:
Consider the car driving straight on the entry to the tunnel. In this condition, the slip angles on the front tyres are equal to the static toe angles but opposing left to right.
Assuming 1mm of toe = arctan(1mm/13") = 0.35deg.
Using the ISO convention, that means left and right slip angles of:
Left = +0.35deg // Right = -0.35deg
...occur from driving in a straight line.
During the light curve in the tunnel, the car turns right and the slip angles move in a NEGATIVE direction for both tyres. You can see already that the right (inside) wheel is already negative so it will increase its slip angle. The outside wheel is positive so first it must decrease its slip angle. So its possible that the outside wheel can have zero slip angle while the car is cornering.
To see if this is realistic for the case of the Monaco tunnel we can make a little model (concentrating on the front axle only)...
Input data:
mass = 650kg
distribution = 45%f
driver: Alonso
laptime: -0.6s
LatAcc = 1G (guesstimation of lateral acceleration through the tunnel)
Front cornering stiffness = 4830N/deg per tyre [Milliken F1 tyre c. 1993]
Assumptions:
Tyres are in the linear range
No lateral load transfer
This results in a front axle slip angle of -0.296deg
Note, this is very similar to the static toe value. If we then superimpose the slip angle from the static toe to the axle slip of -0.296deg we get the individual wheel slips:
Left slip = 0.35 - 0.296 = 0.054deg
Right slip = -0.35 - 0.296 = -0.646deg
So we can see that the left (outside) wheel has very little slip angle compared to the inside one which is doing pretty much all the work.
If we use the cornering stiffness then to find the indiviual wheel Cornering forces we get:
Left = 0.054deg x 4830N/deg = 241N
Right = -0.646deg x 4830N/deg = -3111N
Which confirms the outside wheel is not only doing nothing but its lateral force is slightly towards the outside of the turn. This is not a problem because this corner is not grip limited.
If we assume the car is doing 200km/h at this point we can calculate the power input to the tyre which creates the temperature increase that we see from the onboard camera:
P_left = Vel * SlipAngleL * ForceL = 11 Watts
P_right = Vel * SlipAngleR * ForceR = 1943 Watts
So this is why you see the temperature increase on the inside wheel. It is receiving approx 2kW of heating while the outside wheel receives only 0.011kW.
In conclusion, its the static toe angles which are causing an offset to the left and right slip angles. In a low acceleration corner, the slip angles are so small (due to the high cornering stiffness tyres) that the slip angles are just barley enough to cancel the static toe slip on the outside wheel.
Why don't you see this in other corners? In a normal corner which is grip limited, there is significant lateral load transfer which means the outside wheel has a much larger cornering stiffness than the inside wheel. Also, your slip angles will be significantly more than the static toe so there is no chance that the outside wheel is running at zero slip.
I think a case can be made for anti-Ackerman. With the outer tire more heavily loaded, it will determine the cornering arc. By pointing the inside tire at other than the Ackerman arc a drag force will be generated to help turn the car. This is particularly true at courses with low speed U-turns. So what being seen is perhaps an incidental artifact of the low speed set up.
Ant-Ackerman is more desirable since the camber more favorably presents the tire from the inside out than from the outside in during the dragging event.
