Published on March 14th, 2018 | by Nicolas Zart0
Electric Car Drivetrain Freedom Offers Better Safety — Part I
March 14th, 2018 by Nicolas Zart
As part of a broader series of articles, we’ve asked a few CleanTechnica writers to give us their thoughts on whether electric vehicles (EV) are inherently safer than their internal combustion engine (ICE) counterpart.
Here is part one of a series focusing on the variety of EV drivetrain layouts. But before we dive into it, how about…
Imagine walking into an electric vehicle (EV) store of the future and talking to a friendly helper who is asking you if you would rather have a traditional propulsion design for your EV or something a little more tailored to your needs?
The Incredible Choice EV Propulsion Drivetrain Offers
A decade ago, Franz von Holzhausen, head of Tesla design, told us how excited he was about “secretly” working on what would then become the Model S. “Nicolas, you can’t believe the freedom of designing a car without a gasoline engine or gas tank!” And the Model S results speaks for itself. In fact, it has shaken the entire traditional car industry with many wannabe “Tesla killers” and still little to nothing to show for it, a decade later.
Overall, EV design has opened up a welcome breath of creative freedom compared to traditional car making. The best part is that an EV’s drivetrain can come in a variety of layouts, which is perfect for maximizing the sales of a single unit into various market segments.
While, so far, weight is the boogeyman everyone is hunting down, different companies have tried various drivetrain layouts with success.
If you start with the entry-level Mitsubishi i-MiEV or the Smart ED, you can see the technology is about as simple as it gets. And at the other end of the spectrum, you have cars like the Monegasque Venturi or the even wilder Eliica — eight wheels are driven by eight electric motors that constantly monitor the state of the road and compensate for a wild ride.
And then, there are the wild ones out to prove that the electric drivetrain is the way to go not only for the future of consumer cars but also when it comes to raw performance. Whether they sport two, three, four, or even six wheels, EVs offer such a wide breadth of drivetrain choice that even exotic carmaker Pagani is now ready to make its own EV and join the Tesla/Ferrari/Porsche race. In the meantime, early EV player Rimac, which continues to develop its amazing platform, and new players such as XING are pushing the boundaries even further. We haven’t seen this since the 1930s!
One, Two, Four, or Six Electric Motors?
You’d think only one electric motor is enough for a two-wheeler, but our experience has proven multiple electric motors offer a lot of fun for a little more purchase price. And not just for cars, but for bicycles also. We had the pleasure of test riding an Emotion EVO Big Bud Pro AWD with a motor in the front and back wheel and found it to be so much fun in almost any situation with those big fat tires. Twin motors on electric bicycles (e-bikes) are a lot of fun. It offers a lot more traction and silly fun in gravel, sand, and snow.
EVs, whether in a roadster, sedan, or bigger format, typically come with one electric motor connected to the rear or front axle. Most of the time, that one electric motor drives four wheels, which can be a 4×4 or a four-wheel-drive setup. In a more recent Mitsubishi test drive we did this year, we were well reminded of what two electric motors can do on an SUV like the Outlander PHEV. It felt lively and zippy, and certainly nothing like what we expected an SUV would do.
The In-Hub Unsprung Weight Conundrum
Every promising technology comes with its own caveat, and the in-hub idea has a little problem, which is unsprung weight. Basically, any weight outside the center of gravity adds more push and pull on the motor and affects the overall dynamics of a car. Simply put, it theoretically is less stable. But having a motor on each wheel, while adding to the extra unsprung weight, also gives the car the possibility to adjust each wheel to deliver the right amount of torque. In other words, EVs with in-hub motors have a fine amount of tweaks it can do on the fly with the motors on each wheel.
But if EV unsprung weight is a little tricky, think of traditional handling technology that uses the car’s brake to re-establish balance. It’s simply not efficient compared to how an in-hub electric motor handles dynamic handling.
Conclusion: Are Some Drivetrains Safer Than Others?
Although it would be nearly impossible to answer that question definitively, when it comes to EVs, we can certainly say that the vast choice of drivetrain layouts help improve car safety in general. Stay tuned for part two.