Tesla Chief Engineer Peter Rawlinson geeks out with us about Model S design
Did you sit through all three of the lengthy, expository videos that lovingly and exhaustively detailed every aspect of the Model S's design and engineering? If so, you'll be familiar with Peter Rawlinson, Tesla Chief Engineer and genuine car nut who, in previous lives, held the titles of Chief Engineer of Advanced Engineering at Lotus and Principal Engineer at Jaguar. His latest creation, the Model S, shares some frame concepts the products of one of those companies and some styling cues from another, but it's safe to say this is an all new car that has been obsessively designed starting with a "blank computer screen" as he puts it. He was kind enough to spend some time talking tech with us, and you can read the highlights below.
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The Model S, though naturally having a radical powertrain, has a suspension setup that doesn't look exactly other-worldly, but that's not to say it's entirely normal. It's double-wishbone up front and a multi-link setup in the rear, with the motor attached to a subframe and situated between the rear wheels. The battery pack keeping the show on the road is not situated behind the driver like in the Roadster, rather forming a sheet that looks to be about four inches thick. This sheet is is a structural member of the car, helping the chassis to resist twisting. It's the lowest point in the car (other than the tires), sitting about level with the hubs on the wheels. Peter indicates that this gives the car an unusually low center of gravity, which helps to reduce the amount it rolls in corners.
It's so low that the car, despite its considerable 4,200lb bulk, can make do with relatively thin anti-rollbars. We asked Peter if we're getting to the point where the CG is so low, beneath the roll center of the car, that it would actually cause it to lean into corners. The Model S isn't quite there, apparently, the roll-center is still below the center of gravity of the car, but according to Peter having a car that leans into corners is apparently not as desirable a suspension effect as we'd have thought, causing an unsatisfactory driving sensation, among other things. So, that won't be a problem here.
The car will be offered in three ranges, with battery packs offering 160, 230, or 300 miles worth of juice. Each pack will be the same physical size and each can be removed in under a minute -- assuming you have your sockets handy. About 30 bolts are entailed and, while we still don't have hot-swappable battery stations available anywhere, Peter indicates that's absolutely still a goal for the Model S. That said, 480 volt charging will be supported by the car, which in other EVs provides an 80 percent charge in about a half-hour.
The motor itself is a variation on that sitting amidships on the Roadster, this time liquid cooled, as are the batteries, enabling the car to maintain optimal temperatures. There is no transmission as such, just a simple reduction gearbox and differential. Peter wouldn't quote any drivetrain loss figures but indicated it'd be considerably lower than your average five speed setup, which can range between 10 to 20 percent of power gone simply due to friction. Additionally, the motor controller is integrated right onto the unit itself, with a direct bus connection that cuts down on electrical losses.
And what about that controversial interior? The one with the 17-inch, Tegra-powered touchscreen stuffed in the center stack? Peter calls this a "signature feature" of the car, and of course you can't argue with that, but we do have our concerns about usability. "Seeing is believing," according to the man and, given as we still haven't seen it, we'll go ahead and continue to have our doubts.
We're told the Model S is still rolling toward a release next year and still targeting that $57,000 price tag that Elon Musk assures us will be profitable for the company. What's it like to drive, and just how well can that touchscreen cope to the various greases and industrial components used in American fast food? For those answers we're just going to have to wait a bit longer.
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