xpb That went really wrong at Mercedes
29.03.2018
G Is that how you feel? When Sebastian Vettel took to the track again in front of Lewis Hamilton after his pit stop at the Australian GP, we all had a big question mark on our faces. Of course, we know that in a VSC phase the usual rules for the delta that you need to stay in the lead are overridden. We also suspected that the difference to a normal stop would be between 8 and 12 seconds, depending on the race track. But at the end of the 25th lap, when the race was still under green, Vettel was only 11.3 seconds ahead of Hamilton. That didn't seem to be enough for us.
The Ferrari was 3.9 seconds ahead of the Mercedes on the next pass. Vettel had just finished his pit stop and crossed the finish line in the pit lane while his opponent came out of the last corner. Still at VSC speed. By then the race for Hamilton was over. Afterwards there were all sorts of explanations, with miscalculations, wrong assumptions and a hag who made the most of the situation. But what really happened? Why was 11.3 seconds enough to stay in the lead? And why was a calculation error of only 2.4 seconds so decisive for the war?
This is how VSC gives Vettel free time on the track
To understand what really went on this 26th lap , you have to study some lap logs and see where the individual cars are relative to each other. Let's turn the wheel back a lap. Crossing the finish line lap 25: Vettel leads with the following distances from Lewis Hamilton, Kimi Räikkönen, Daniel Ricciardo, Fernando Alonso and Max Verstappen:
Let's forget Ricciardo and Alonso. Like Vettel, you will pit a lap later to change your tires and benefit from the VSC phase. At this point the race is still running normally. Only where Romain Grosjean has parked his HaasF1 is a double waved yellow flag shown. The race time is exactly 37:52 minutes when race director Charlie Whiting presses the VSC button.
At the moment, Vettel is driving through Turn 8 and is in the middle of the second sector. Hamilton accelerates out of turn 4. That is around 350 meters from the first sector border. At this point, his deficit on Vettel has grown to 11.6 seconds or around 700 meters. Maybe he twitched the yellow flag more than Vettel. Only for information:Alonso has passed the finish line at that moment, and Verstappen is in turn 15, albeit still on his 25th lap.
Now there is a phenomenon that many overlook. Vettel gains more time for free on the rest of the lap, although the distance between him and Hamilton does not increase in meters. From that moment on, both have to drive equally fast. So 700 meters remains 700 meters. But 11.6 seconds doesn't remain 11.6 seconds. Because Hamilton covers the 700 meters to the place where Vettel got the VSC signal more slowly than Vettel did.
Vettel's lead grows in this range. Hamilton would of course get the lost time back at the end of the VSC phase for the same reason. But if one of the two drivers pits in between, the picture changes. Because the time gain gives Vettel a position. It doesn't matter if Hamilton makes up time afterwards. The damage is done.
Hamilton loses too much time after the VSC signal
When Hamilton reached turn 8, his gap to Vettel increased to 18.5 seconds. Here again the distances to Hamilton in turn 8 measured with GPS:
The distance, which has increased by 5.9 seconds, is more than it should actually be due to the distance and the speed delta. In comparison, Raikkonen loses less ground with 2.3 seconds, although in relation to Hamilton he is much more affected by driving longer at a slower speed. Hamilton has left a second in this area, which is his account. But there is a good excuse for that.
Team principal Toto Wolff said that his driver received the VSC message in the middle of a curve. As of this year, the regulations require that drivers must be positive at least once in each of the 19 mini-sectors from the moment the VSC message is received. There is no longer a transition phase.
FIA
on the diagram SC lines 1 and 2 are shown. The VSC delta does not apply between these lines. A pit stop takes just as long as under normal racing conditions.
Hamilton may have taken off the accelerator a little too abruptly while he was in the middle of acceleration, trying to make sure to stay positive. Even compared to Verstappen, who was affected by the VSC rule for the entire round, Hamilton does not make up the time that he would have to make up arithmetically. At least the Englishman was able to give full throttle in the first sector for 24 seconds. Verstappen nowhere. Even so, the Dutchman only lost 3.6 seconds on lap 26. That is actually not enough.
However, the Mercedes strategists do not see the small loss of time at the beginning of the VSC phase as decisive: “Because Lewis can make up for the time lost there later. It has to remain positive on average in all mini-sectors, so it can compensate for small time losses later. ”
It happens exactly the same way. Hamilton catches up another 1.2 seconds on the rest of the lap until Vettel turns into the pits at turn 15. The same tendency can be observed with Raikkonen. Vettel even wasted a little time in this area. Here is the position of the first three with Vettel in turn 15:
At the Safety Car 1 line, Formula 1 arithmetic gives the Ferrari driver a second gift. He is allowed to give full throttle from here to the pit entrance, from which the speed limit is 60, while outside the race continues at VSC speed. The time from pit entry to pit exit including pit stop is the same as in a normal race. After the end of the pit lane to the Safety Car 2 line, full throttle is the order of the day. Then the driver has to adjust to the VSC speed again. But Vettel was already ahead.
The Mercedes computer calculated that the advantage of the VSC pit stop was exactly 9.8 seconds. So far he still calculated correctly. The 2.4 second error arose either in the calculation of the time that Vettel would make up for in the rest of the lap thanks to his advanced position, before he comes to the pit stop. Or as chief engineer Andrew Shovlin explains: “Of course we feed our program with the data that we determine during on-site training. We test how much time it takes from the SC1 line to the pit entrance. It looks like this test was flawed. ”
We now know: the algorithm is OK. The error was caused by entering incorrect parameters. According to Shovlin, however, you could have saved yourself the entire discussion if you had given Hamilton a different target between round 20 and 25. “We could have driven faster in this phase, but we let Lewis drive certain times with regard to the tires and fuel consumption. Our computer told us we were on the safe side. In retrospect, it was a tactic with insufficient security reserves
