Theory on Richard Hammond’s Rimac Car Crash

Richard Hammond's Rimac Concept One crash in Grand Tour show.

Before I begin this post, I think it would be important for me to qualify with a statement about electric cars. I am in no way antithetical to electric cars. The possibilities that they would bring is immense. The fact that it has less moving parts translates to less transfer of energy, which would make it much more reliable and cheap to operate. I have my eye on a few models at the moment and is planning to buy one once I start ballin 😎. That being said, I think current nature of electric cars is the primary reason why Hammond crash.

Mind of Race Car Driver

I am no Neuroscientist. Hammond is no Race Car Driver. But those who have watch F1 or any motorsports are aware that the mapping corner to optimal racing line and speed to take in that corner is a task explored by drivers in early part of the racing event, e.g. Free Practice sessions in Formula 1. Despite being at the top echelon of the racing craft, Formula 1 drivers go off track multiple times in the hopes of learning the optimal line and speed in a given corner. Another reason why these race car drivers go off track is that they are testing new changes or upgrades in their car. They will hope to sort this out during the practice sessions in the hopes of using it optimally during qualifying and race. In Hammond’s case, I argue that this is “change” is the move from a conventional Internal Combustion Engine to an electric car. More specifically the very nature that current electric cars are heavy.

How Weight Affect Racing Cars

Racing cars tend to have a high horse power engine and light weight. Formula 1’s 2017 minimum weight regulation is 728kg, with Ferrari’s engine being rumored to be around 1000hp. The same power is in Rimac Concept One, but weighs 1850kg, 2.5x the weight of a Formula 1. Of course, Formula 1 and Rimac are two different species. Formula 1’s . To eliminate variances such as aerodynamic, suppose the Formula 1 is also 1850kg in weight but have everything else the same. K, I’m gonna have fun here. Let the original Formula 1 (SF70H) be Car A 😎, and the heavy one is Car B (JK 😉, don’t get mad). Despite my joking around, still, pretend they both have the same aerodynamic.

Car A
Car B

Suppose the both cars take the infamous Parabolica of Autodromo Monza at the same speed. A corner with about radius of 72m. One thing we know for sure already. Since they both have the same aerodynamic, they will both have the same downforce. But how much centripetal force?

Parabolica Section of Monza Circuit

For the real Formula 1, Car A. Cars are often described “apexing in fourth gear at 215 kilometres per hour (134 mph)” in this corner. This means that the car is taking that maximum amount of centripetal force in that apex. To determine the centripetal force of both cars, I’m going to consult my old high school physics notes.

Centripetal Force formula:

\(F_{\text{centripetal}} = \frac{\text{car mass } \times \text{ apex velocity}^2}{\text{corner radius}}\)

For Car A,

\(F_{\text{centripetal of Car A}} = \frac{728kg \times 215\frac{km}{h}^2}{72m}\)
\(F_{\text{centripetal of Car A}} = \frac{728kg \times 59.77\frac{m}{s}^2}{72m}\)
\(F_{\text{centripetal of Car A}} = \frac{728kg \times 59.77\frac{m}{s}^2}{72m}\)
\(F_{\text{centripetal of Car A}} = 36121N\)

So for the real Car A, the centripetal force is 36121N (translating to about 5G). Since the car is not slipping at this centripetal force. 36121N is also the sum of the downforce of the aerodynamic and frictional force of the tire. Suppose tire have static coefficient friction of 1, then frictional force is \(728kg \times 9.81 \frac{m}{s^2} = 7141.68N\) and downforce is \(36121N – 7141.68N = 28980N\).

For imaginary Car B, the centripetal force would be 91792N, 3x the centripetal force of Car B!! Again, it experiences the same aerodynamic downforce of 28980N. But is this realistic? Does it have the tire? The frictional force? Car B’s frictional force is \(1850kg \times 9.81\frac{m}{s^2} = 18148.5N\). The amount of force holding Car B inside the corner is the sum of downforce and frictional force, which is \(28980N + 18148.5N = 47128.5N\), which is only half the centripetal force it is experiencing. This means, that Car B has to take this corner significantly slower. About 152kmh. 60kmh slower!

Conclusion

Back to Hammond’s case. Watching the show, most cars that Hammond have driven are relatively light compared to the Rimac Concept One. At that corner in that hill, Hammond’s brain calculated that he can take it at a speed suitable only for a lighter Internal Combustion or Hybrid sports car. The moment Rimac Concept One hit that corner, although downforce might be similar to other sports car, centripetal force would be through the roof.

Again, I don’t hate electric cars. But they are simply too heavy at the moment. I realize early on that the bottle neck is the battery. I used to check United States Department of Energy site almost regularly. This is to check for the list of their grants on prospective battery technology. Well, that was half a decade ago. I’m sure these new lighter more high capacity battery will come, but I doubt it will see Formula E rivaling Formula 1 anytime soon.

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