Think about you’re the race engineer for <insert your favourite driver identify> and your aerodynamics division have simply spent 3 months engaged on a brand new improve, your driver runs it and says: “it’s utterly undrivable, there may be an excessive amount of understeer in low velocity mid nook however I can not add entrance wing as a result of excessive velocity will turn out to be nervous, and entries to low velocity are unstable”.

That is the traditional downside of poor by way of nook steadiness which may actually maintain the driving force again in with the ability to exploit the utmost efficiency from an improve. A technique to assist alleviate the issue is to vary mechanical steadiness by way of the nook. This might be achieved by altering the anti-roll bar (ARB) geometry. Right here we’ll check out the impact of fixing the ARB pickup inboard.

Firstly we’ll have a look at the impact of displacing the ARB pickup inboard within the each x and z. We are able to do that by operating 2,000 simulations which discover the impact of fixing this facet of the suspension geometry. In Cover we name this an “exploration” — we’re actually exploring the consequences of various any variety of bodily parameters on the efficiency of the automotive.

By altering the pickup level in x and z, we alter the kinematics which can have an effect on the ARB lever arm size so we’ll additionally throw the entrance and rear ARB stiffness parameters into the exploration to permit us to compensate for this.

When you’ve run 2,000 simulations it’s not a lot use going by way of them one after the other to search out one you want, so we’re going to make use of a few of our visualisation instruments to grasp the consequences of our geometry modifications. Determine 2 reveals the parallel coordinates plot which we’ll use to assist us goal the fascinating areas.

Right here we see our 6 simulation parameters (ARB stiffness at each the entrance and rear, x and z displacement of the ARB pickup inboard level) and solely a few simulation outputs to maintain issues easy (laptime and roll stiffness). We are able to transfer the red line to discover the outcomes floor and infer the output for combos which haven’t been run. On this case the red line has been moved to characterize the baseline automotive setup. We’ll then spotlight solely the outcomes with the quickest laptime. We don’t simulate trip efficiency (but!), however we need to make sure that we’re not making the automotive too stiff by highlighting solely the simulations which have an general roll stiffness lower than or equal to the baseline. We are able to see that there are a variety of runs which fulfill this standards and are faster than the baseline, so we’ll do some additional investigations.

If we repeat the exploration for the entrance solely, we are able to solely enhance upon the baseline laptime of 78.71sec by a number of ms (spoiler: the vary of entrance heave journey is just too small for the area we’re exploring entrance ARB geometry in), due to this fact the advance should be coming from the rear. Repeating for the rear by itself reveals a possible enchancment of 54ms. Whereas this won’t appear to be a lot, the flexibility to constantly choose up chunks of efficiency like that is what separates the good groups from the remaining. We are able to see from the parallel coordinates chart that that is achieved by shifting the ARB inboard pickup upwards and rearwards (-ve rARBPickupInboard[2] and -ve rARBPickupInboard[0]) with a softer ARB to compensate for the discount in lever arm. The ensuing geometry is proven in Determine 3:

This seems to be similar to merely rotating the ARB at setup (automotive stationary at 0kph), which might be very straightforward to realize by shortening the inexperienced drop hyperlink; so we re-ran the exploration, however as an alternative of permitting the ARB pickup inboard to have freedom within the x-z airplane we restricted it to the arc constructed from the rotation of the ARB. We discover that an preliminary rotation of the ARB of 60deg up from horizontal (as proven in Determine 3) and a softer ARB to compensate improves our laptime by 51ms, so we acquire a lot of the profit however solely want to change the drop hyperlinks.

What impact does this have? As a consequence of downforce, the rear trip peak drops as we go sooner (see Wind and gradient at the Belgian GP to grasp the significance of rear trip peak). This causes the push rods in Determine 3 to drive the drop hyperlinks down through the rocker and rotate the ARB. This will increase the ARB lever arm (examine Determine 3 and Determine 1), which has the results of successfully softening the ARB in excessive velocity. This causes a distinction in mechanical steadiness between low velocity and excessive velocity.

If we have a look at mechanical steadiness (rStiffnessBalF) by way of the velocity vary in Determine 4 we see that in low velocity (100kph) the mechanical steadiness is 5.2% rearwards relative to the baseline as a result of much less leverage on the ARB. At excessive velocity (round 200kph), the ARB has rotated as a result of drop in rear trip peak, so the lever arm has elevated and the mechanical steadiness is now matched to the baseline.

We’ve matched our excessive velocity steadiness, however how does this assist our low velocity by way of nook steadiness? If we have a look at ΔrLatBalF (distinction in mechanical steadiness between baseline and rotated ARB at setup) by way of Flip 13 and the final chicane in Barcelona (Determine 5), we are able to see that on entry the mechanical steadiness is barely forwards of the baseline (much less entrance grip and extra rear mechanical grip) which provides us a extra steady automotive when the driving force stamps on the brakes. Because the automotive slows down and the driving force desires to show in, the mechanical steadiness is now 2% rearwards of the baseline which permits the rear to withstand extra of the rolling second of the automotive; the outcome being a extra even lateral weight steadiness on the entrance tyres, leading to much less entrance locking and extra entrance grip. At mid nook the mechanical steadiness is as much as 6% rearwards (cursor {position}), giving an enormous enchancment in entrance grip when the driving force is attempting to show the automotive (much less low velocity mid nook understeer).

Sadly, as with all the things in F1, this doesn’t come with out a draw back; as the driving force applies preliminary throttle to speed up out of the nook, there may be much less rear grip till the automotive has gained some velocity, which may make the automotive barely extra nervous on preliminary traction. Nonetheless, the positive factors by way of entry and mid nook on this instance are sufficient to go away us 51ms forward on the finish of the lap with a happier and extra assured driver. Not unhealthy for a morning’s work!

After all we may method this downside from one other angle. As a race engineer you would possibly determine that one of the best ways to repair this downside is to maneuver mechanical steadiness rearwards at low velocity mid nook relative to entry/exit, whereas preserving excessive velocity mechanical steadiness. On this case you may spotlight runs on the parallel coordinates plot the place in excessive velocity Flip 9, the mechanical steadiness is analogous or barely forwards of the baseline, whereas in low velocity Flip 10, mechanical steadiness is rearwards. It is rather satisfying that this methodology produces the identical finish outcome.

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