I’m taking a break from answering questions to tell you things about Nikola Tesla that piled on me this week. But before I start, here are a few quick answers:
- Cost-effectiveness of owning a Tesla Roadster: No doubt about it, a Tesla Roadster never will pay for itself in dollars compared to (for example) a Ford Focus. But then again, when you drive a Focus, are you paying for your share of global warming? How about your share of our adventure in the Middle East? How much is “the earth” worth? How much is our national security worth? When will you pay for it? People who buy Tesla Roadsters or even hybrids (or solar panel arrays, which have a longer return on investment) know perfectly well that their “investment” will not always pay for itself in cash. The payoff is on a different plane. (And you will have a hell of a lot more fun in a Tesla Roadster than in any Ford. :) )
- Electric grid efficiency: Somehow people get the idea that the electric grid is massively inefficient, but this just ain’t so. Check my references in the whitepaper, The 21st Century Electric Car. The average efficiency of the U.S. grid is 92 percent.
- White Star test drives: It will be a while before we can talk about test drives for White Star, our four-door family car slated for the 2009 time frame. We still are in the very beginning of the design phase! Patience…
- Lotus Europa: The Europa does not share components with the Tesla Roadster except in that it also uses common parts from the Elise (e.g., the windshield surround, wiper system, and many safety systems including airbags, aspects of the brakes, front suspension, and the steering gear). The Europa was not known to us at Tesla Motors when we developed the Tesla Roadster. Any similarities (especially in styling) are only coincidental and superficial.
- Motor frequency: The motor makes one revolution for every two cycles of its three-phase AC input. So when the motor is turning at 13,500 RPM (which is 225 revolutions per second) the AC frequency is 450 cycles per second.
- Copper rotor: Anatoly Moskalev, in a recent post to my Motor City blog, astutely points out that “…copper in its pure annealed form (most conductive) is very soft metal mechanically. But most highly conductive part of a rotor has to hold biggest mechanical stress because forces from electromagnetic field are applied mostly to areas in rotor with highest current. So making mechanically robust rotor from soft metal trying to minimize its mass is a real challenge.” Exactly. But we do use pure copper; making it mechanically robust is part of our secret sauce. :)
- Motor efficiency in general: Yes, I have seen believable claims of AC induction motor efficiencies greater than ours, but as far as I can tell, these are ideal efficiencies – at the particular motor’s ideal speed and load. Our motor was optimized to provide decent efficiency over very wide RPM and load conditions – its efficiency map is very flat. The numbers we quote are not the peak efficiency of our motor, but the average efficiency expected over the course of driving through the EPA’s highway driving schedule.
- Hub motors: What's with the obsession about hub motors? Or to put it more succinctly: What problem - what actual, real problem - would hub motors solve? They won't improve performance. They won't improve efficiency. They won't improve reliability. They won't improve safety. They won't reduce program risk.
Consider this: A differential is a very simple, reliable, and efficient device - particularly when the motor is transverse-mounted (since the motor rotation axis is parallel to the wheel rotation axis). Note that the internal ("differential") gears in a differential do not turn except when cornering - and then only slowly. The differential simply acts as a ring gear to match the speed of the motor to that of the wheels. Similarly, half-shafts with CV joints are also simple, reliable, and efficient – especially when driving rear wheels, since they don't have to bend with steering.
The penalties for using hub motors include: 1) More unsprung mass. (Note that there is no way that you can eliminate brakes and still have a safe car! The Federal Motor Vehicle Safety Standards won't allow it anyway.) 2) More total motor mass for the same total power. Two (or four) smaller motors are of necessity heavier than one larger motor of equivalent total power. 3) Replication of motor inverter electronics. Each motor will require its own expensive, complex inverter. In the end, a differential plus a pair of shafts is more reliable and more efficient than a second inverter and a second motor - especially when the two inverters must act in coordination. 4) We would be forced into a motor type that has less than ideal torque characteristics. The AC Induction motor provides the best overall torque characteristics for a car. Unfortunately, this type of motor does not work well in the pancake format needed for a hub motor. Bottom line: Tesla Motors chooses its technologies based on actual performance and actual feasibility. We shy away from technologies that are merely trendy or only look good on paper. That's why we use AC Induction motors instead of hub motors. That's why we use Li-ion batteries instead of ultracapacitors. That's why we use aluminum instead of unobtainium.
- Friesen motor: When someone claims they can improve our efficiency by 40 percent, you have to wonder how, when our motor is already running in the neighborhood of 90 percent efficiency. It seems to me that there is a theoretical upper limit for improving our motor of about 10 percent... A claim of 40 percent improvement should set off all our bullhalibut detectors.
- Jobst: Yes indeed, our technology is not that different from what’s used in trains. The big differences are mass and storage. The kind of mass optimization that we have done would make no sense on a train. (I’m not an expert on trains, but I suspect that up to a point, mass actually helps trains get traction.) Since electric trains have infinite “storage” on the third rail, there also is not quite the need for motor efficiency.
My answers weren't so quick after all. But I still want to tell you about an award we won and, as promised, some things about Nikola Tesla.
Tesla Motors had the distinct honor to receive a Product/Industrial Design Award from Global Green, Mikhail Gorbachev’s organization focused on solving the big environmental issues. Elon and I accepted the award behalf of Tesla Motors at the Global Green awards ceremony in New York last Monday (October 16, 2006).
My wife, Carolyn, and I, together with Elon and his wife, got to sit at the head table with Gorbachev. His daughter, his translator, three other award recipients, and the president of Global Green also sat with us. It was incredibly interesting, and the audience of about 450 people was very enthusiastic about Tesla Motors. (Several became customers that evening, breaking through 200 Tesla Roadster customers!)
During the intro, a video was shown highlighting some of Global Green’s projects. It turns out that in her previous job, Carolyn managed a portion of the design of a facility in Russia that destroys chemical weapons. This facility was shown in the video, and Carolyn got a big handshake from Gorbachev when his translator pointed this out. Needless to say, this made her evening. (She says that seeing me receive the award made her evening, but I know better. :) )
Unpaid advertisement: Global Green introduced us to Ozocar. These guys provide limo service in New York using hybrids instead of big ol’ Lincolns. Not only do they get vastly better gas mileage than the black limos, they also have decent wireless access in the cars, as well as a laptop computer that that you can use to get online during the ride. And our driver was awesome.
But that’s not what this blog is about… We had all day Sunday to hang out in New York City; the first time for my wife and me together. We did some of the usual tourist stuff, including the 102nd-floor observation deck of the Empire State Building. (A cliché, but awesome none the less.) We went to Times Square to buy t-shirts for the kids and to check out the electronic billboard where the RIM guys allegedly paid for a billboard of me holding my Blackberry Pearl in front of a Tesla Roadster. We also checked out the Main Branch of the New York Public Library. If you’ve never been, go see this place! Next door in Bryant Park, there was a cool “meet the author” signing event that reminded me of the fun I had doing the Rocket eBook thing.
But the focus of our tourism was to check out some of Nikola Tesla’s haunts. We spent some time at the Hotel New Yorker where Tesla spent his later years and ultimately died. It was kind of depressing.
There was a decent plaque on the wall, but some truck had run into the marquee of the hotel and it looked even more run down than it normally would. Around the corner on the hotel wall was a window display of the various famous folks who’ve stayed at the New Yorker. Among the many was a photo of Tesla very late in his life shaking hands with the King Peter II of Yugoslavia in his dingy room at the New Yorker. Very surreal.
We found our way right back to Bryant Park (much to our surprise) to discover that the corner of 6th Avenue and 40th Street is officially Nikola Tesla Corner. Seems that back in the day, Tesla liked to stop and feed the pigeons at Bryant Park.
One-hundred-and-fifty years after he was born, there are still quite a few traces of Tesla’s time here in America, if we look. We tried to find the Radio Wave Building, where I am told there is also a plaque commemorating his work but we somehow got lost. Next time…
To round out our spooky tourism, we visited Strawberry Fields in Central Park then across the street to The Dakota, walking on the sidewalk where John Lennon was murdered. Strange that there’s a movie with David Bowie playing Nikola Tesla and a movie about Lennon in the theaters at the same time. Note that Bowie and Lennon were good friends, and collaborated on several songs, including Fame.
When I got home, my friend, Laura, emailed to say that NPR ran a fascinating discussion about the new multimedia opera called Violet Fire about the life of Nikola Tesla that is receiving rave reviews in New York. (Anybody seen this opera yet?)
The same morning, Laura also heard Senator Barbara Boxer on the radio on the World Affairs Council extolling the virtues of the Tesla Roadster – its speed, panache, and beauty, and especially its solar payback potential. Win-win-win, she said. (Senator Boxer visited us a little while ago and definitely enjoyed herself.) Laura says she’s surrounded by things Tesla. Too bad Senator Boxer’s extemporaneous endorsement didn’t make the "official transcript" on her website. Have any of you found a transcript of what she actually said?
To complete our Tesla weekend, Carolyn and I saw The Prestige. How could we resist? David Bowie playing Nikola Tesla. How cool is that? I think the movie was excellent, though I was annoyed by some of the details. For example, Tesla is shown lighting up light bulbs without any wires – a trick he was known to do. But the bulbs he was using in the movie were incandescent filament bulbs – the bulbs invented by his nemesis, Edison. Tesla actually did this trick with the florescent bulbs that he invented. Worse was the portrayal of Tesla as having invented teleportation (actually not quite teleportation, but I don’t want to give away the movie for those of you who still need to see it :) ). This will only feed the mysticism surrounding Tesla, rather than restoring Tesla’s place as a true scientific genius.
But Bowie makes a mighty fine Nikola Tesla – all he needs now is his own Tesla Roadster. David – are you reading this blog?