January 2008 Archives

Tesla Owners Town Hall #2

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Tesla Motors hosted a town hall meeting today, with attendees in San Carlos and over the phone. This is my summary of the major points according to my notes. Expect a full audio recording of the call to be made available on Tesla Motor's web site as soon as possible.

Elon Musk started by reaffirming their commitment to both the Roadster and the White Star sedan. Roadster customers are helping to support Tesla's long term goal to get into the mass production of electric vehicles.

JB Straubel briefly described the plan announced last week to move to a single-speed transmission (really just a gear box) and meeting the original performance specs by sending more current to the motor, using an improved cooling system to allow for increased heat dissipation. This new gearbox is what the White Star team has been working on, and isn't just a last minute scramble to solve the Roadster's transmission issues. The single gear ratio will be 8.27:1, which is between the old first and second gears, closer to second gear. The top motor speed will remain at 14,000 RPM, with a slight chance of modest improvement. The goal for 0-60 time is 4 seconds under real conditions, and perhaps less than 4 seconds under ideal testing conditions. The top speed may come down a bit, but is expected to stay at or above 120 mph. Due to increased efficiency, the driving range may improve slightly, but less than 10%, perhaps in the 230-235 range. The 0-100 time will be improved by having a broader torque curve, likewise the quarter mile time is expected to drop into the 12-second range. These are just goals and estimates, they won't know for sure how it will all perform until they have production units to test and run through the EPA tests.

They will be using the same motor and battery pack, primarily only the PEM (power electronics module, aka the inverter) is changing. The current air-based cooling system will be improved, with as few changes as possible. The White Star will have a liquid-cooled drive train, but they are not implementing that in the Roadster. The increased current sent to the motor is made possible by new parts being available, something that wasn't possible when they originally decided on a two-speed transmission.

With no transmission, the gear shifter is purely an input to the firmware. Drive and reverse simply set the motor direction, and neutral disables power to the motor. There is a park-lock controlled by key-on and key-off, but no "park" position on the gear shifter, just like a manual transmission ICE car.

The change to the gearbox is not expected to require any new crash tests, the weight of the new gearbox will between the two transmissions that were put through the previous crash tests. The changes are small enough that other systems should not be affected. Testing the gearbox will be a lengthy process, starting this summer. They will upgrade their current test vehicles in the US and the UK for early testing as soon as possible.

Regarding risks in the new design, they are working with a very experienced designer with a solid track record. The new gearbox has less than half the parts, and less than half the bearings compared to the two-speed transmission. They have already put over 100,000 miles on the original one-speed prototype gearbox without problems. The new design will reduce weight and cost while also increasing efficiency and reliability.

The new design will have much less backlash than the two-speed, by a factor of three. In gearbox design, there's a trade-off between reducing backlash and increasing efficiency. The one-speed gearbox will perform better than the two-speed transmission in that regard.

The Car and Driver review said the "heavy-use" range is about 160 miles, a bit lower than the 170-mile range previously stated by Tesla's aggressive driving range. That test drive was done in the cold, rain, with the top off and the heater on, and with a heavy passenger, and no restraint using the accelerator.

The Roadster will have multiple driving modes: maximum performance and maximum range were mentioned. These will change how the car drives, and also how the firmware estimates remaining charge.

Elon Musk's car, Production Unit 1, will arrive this Friday, between 11:00 am and 2:00 pm!

Early production begins on March 17th, at about one car per week with the interim single-speed transmission. Production will ramp up, first to two per week, then three per week, as fast as possible without waiting for the new gearbox. Tesla estimates they will be using the new gearbox by vehicle number #100, roughly estimating to have cars in the 400s produced by the end of the year. By 2009, they expect to be producing 40 per week, for a total of 1,500 in 2009.

The 2009 model year Roadster is expected to see a cost increase. Slots that have been vacated in the 2008 model year schedule are going for $125,000. The Roadsters will be a pretty hot item when they hit the road, attracting a lot of attention. One customer asked about a lo-jack (hidden GPS tracking) option as a theft deterrent , and Tesla said they would look into offering something as a delivery option.

The charger is built into the car and charging options are simply a combination of a cable and a firmware setting. The current options are 1) 120V/15A which plugs into a standard wall outlet, 2) 240V/40A which plugs into a dryer outlet, and 3) 240V/70A which requires installing a special charging plug. Tesla is also looking into a pay per use 1-hour charging option that would be available in specific locations to make it possible to charge the car over lunch when making a long distance drive. The current battery pack can handle the rapid charge, which will likely be done using a high voltage DC bypass.

Owners who take one of the early units with the preliminary one-speed gearbox will be able to have the new gearbox swap completed in one day, plus any required shipping time. By the time cars are delivered, there should be Tesla service centers on both coasts, so they don't have to ship cars across the country to do the swap. Tesla may offer these early customers the option to keep the preliminary transmissions (if the 0-60 time isn't important to the customer), with some incentives for doing so.

Tesla expects to reveal a static model of the White Star (and presumably its real name) in the 2nd quarter of 2008, and to break ground on the production facility late 2008 or early 2009.

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This page is an archive of entries from January 2008 listed from newest to oldest.

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