Category Archives: Tesla Motors

Tesla Roadster

What is the Tesla Roadster 1.5, exactly?

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The second generation of Tesla Roadster will look exactly the same, but sport a new “Powertrain 1.5”.  This powertrain is an improved motor, inverter and gearbox designed to replace their previous two-speed transmission that had many durability, efficiency and cost challenges.  The faulty 2-speed transmission effectively forced Tesla to sell its Roadster locked into second gear, dramatically hampering acceleration. The one speed transmission “improves motor torque by a bit more than 30% beyond what was already great and the ¼ mile time for the car is now in the 12.9 second range. The top speed of the vehicle remains over 120 mph,” according to Tesla CTO JB Straubel.

According to Tesla’s site, Powertrain 1.5 makes the following improvements:

  • An improved inverter (PEM) to deliver higher motor current
  • An improved motor to handle higher current and torque
  • A new single-speed gearbox
  • A new motor to gearbox coupler and an improved motor cable
  • Upgraded vehicle firmware
  • NO changes to the battery pack

Tesla Roadster Inside

PEM-green, Battery-blue, Electric Motor-under the PEM

The Power Electronics Module (PEM) basically acts as an amplifier and guide that converts and regulates the power from the battery to the motor. When you put the pedal to the floor you tell the PEM to give the motor some juice. By using newer IGBTs (Insulated Gate Bipolar Transistors) that convert and regulate power from the battery, they have been able to boost the PEM output current by about 33% from 640A rms to 850A rms with the same number of IGBTs.  Fancy talk for using recent advances in electronic technology to make a more efficient PEM and a more powerful Roadster.

The motor has been improved by changing the casting in order to link with the new transmission. The motor terminal lugs have been changed, as well as the cable from the motor to the PEM to improve efficiency and reduce temperature rise.

The heart of the Powertrain 1.5 improvement is in the gearbox. CTO JB Straubel explains it best in his blog:

The new gearbox is the most significant change from powertrain 1.0 to 1.5. We have significantly reduced the complexity of this gearbox by getting rid of the need for shifting or speed matching between two gear sets. There is only one set of gears that is always engaged with a ratio of (8.2752:1). There are no clutches and we have also done away with the need for an electric oil pump and instead integrated a very efficient gear-driven oil pump into the gearbox. All of these simplifications have saved a great deal of mass and the new gearbox is approximately 45kg instead of 53kg for the old two-speed design.

This mass savings is even more impressive when you consider that we have designed this transmission to have a long life at a much higher input torque (400 Nm) and higher speed (14,000 rpm).

The engineering design of this new gearbox has been finished for over a month and we are now running prototypes through their paces on dynamometers. We built two initial gearboxes with machined aluminum housings so we could gain some early test results before finalizing the cast housing tooling and machining fixtures.

One of the most exciting features of this new gearbox (from an EV perspective) that we have been able to validate on the first prototypes is that it has extremely low spinning drag (less than 0.1 Nm of dry drag torque.) This is less than any other gearbox we have tested with the only possible exception being the EV1 gearbox. This low drag contributes to the 1.5 powertrain having a slightly improved range figure.

The two pictures below show some of the gears and shafts. On the left is the input shaft assembly…spinning up to 14,000 rpm bearing selection is very important. The spline on the right connects to the motor coupling. The picture on the right is the intermediate shaft assembly. Notice the transmission locking “gear” in the center that engages with a stationary pawl when the car is parked.

All these changes will dramatically improve performance without effecting the range or power draw from the battery.  Tesla has learned a lot from its inaugural launch, hopefully with this more efficient powertrain they will ramp up production.

Sources: [MotorAuthority, Tesla Motors]

Model S

“Rendered speculation” unveiled of Tesla Model S

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Last week, a roadandtrack.com article displayed a picture of this vehicle in its new and future cars section. People are having a tough time nailing down where this rendering came from and its legitimacy. Was it released by Tesla Motors? Or is it just somebody’s best estimate of what the car could look like? A couple months ago, I wrote about some rumors swirling that Tesla had possibly leaked information on the Model S design. I must say, the rendering does share some features with the Rapide: a large, low grill, long, narrow headlights, and four doors. But there are also some disparities: more angular, Asian design influence, and smaller back seats.

I don’t believe the final Tesla Model S will actually look like this rendering for a couple reasons. The Model S project was created to bring a luxury, four door sedan to the electric car market. The rendering shows that the back seats are not really sedan worthy, but more like those you find in two door sports cars like the Nissan 350Z and Audi TT. The photo has been stretched and altered by many websites so it is hard to estimate the length of the vehicle, but the Model S is meant to be a very long and large vehicle. The rendering looks a lot like a Mazda RX8, which is by no means a family sedan.

To add to the confusion, a picture in businessweek shows Chief designer von Holzhausen supposedly with a prototype of the Model S. What we see is the rear of a vehicle that looks like a full on hatchback, nothing like the rendering or the Aston Martin speculation, but more like a Toyota Prius. So it looks like everybody is back to the proverbial drawing board.

Model S, Tesla Motors, Tesla Roadster

Extraordinary Recession Affects Tesla Motors

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Newly appointed CEO of Tesla Motors, Elon Musk, created a new post, Extraordinary Times Require Focus, in his blog today.

He announces Tesla is going to “consolidate operations”, which means “lay off” a few people. This was expected since every car company is getting hit by the economic crisis, even electric car startups. He also had some discouraging news on the Model S:

Tesla is absolutely committed to development of our next generation vehicle, to be unveiled early next year. However, we are going to reduce activity on detailed production engineering, tooling and commitments to suppliers until our Department of Energy loan guarantee becomes effective.

This will delay in start of production of the Model S by roughly six months to mid-2011.

Elon Musk is a very competent businessman, as exemplified by his Paypal success and his SpaceX gig. He also seems to have a genuine passion for electric cars, as he has spent about twice as much money as he expected in the project. So I don’t think a few bad quarters will end the ride.

Model S

Anticipation builds for Tesla’s Model S

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Could Tesla’s $60,000 electric sedan look something like this?

Aston Martin Rapide

That is what many are speculating after The Sun columnist, Ken Gibson, claimed he was given a “sneak preview” of the Model S at the end of his recent online column. Thus priming the the rumor mill at the telsamotorclub.com Model S potential design forum, and leading many to claim the Model S will look like the Aston Martin Rapide concept. This keeps in line with Tesla’s claims that the Model S will be a huge, very long, four door hatchback.

The design also fits the dimensions of the Dodge Magnum Mule that was spotted next to a Tesla Motors facility with no exhaust pipe and test wheels, also in the forums:
Whitestar Mule

This is still all speculation, but anything rolling out of Tesla Motors is sure to be superbly designed and built, given their track record.