The primary issue that has been preventing Tesla Motors from getting their electric Roadster into full production for the last several months has been the unfortunate tendency for the transmission to self-destruct in only a fraction of a car's normal lifespan. In December, the company announced a plan that would see them launch production in the first quarter of 2008 at a slow rate with an interim single-speed transmission in place of the planned two-speed unit while they continued to develop a two-speed unit that could withstand the punishment of the electric motor. Once a newly-developed two-speed unit was validated, Tesla planned to retrofit the early cars with new units.
One of the many questions people raised was why use a transmission at all? Virtually all other EVs just use a reduction gear. Tesla has now come up with a plan to resolve the problem and guess what? The two-speed is history. The two-speed was originally used in order to meet the performance requirements for acceleration and top speed. The solution came from work that was being done for the WhiteStar sedan. In order meet their performance targets, Tesla has modified the power electronics module to be able to send significantly more current to the motor and hence produce sufficient peak power to get the four second 0-60 time. Read on after the jump learn more about what Tesla is calling DriveTrain 1.5.
As was discussed in the previous story about using the Roadster as a track car, the limiting factor there is the heat build-up in the motor. The air-cooled AC induction motor would simply get too hot causing power limiting logic to kick in and not be useful on the track. One of the changes being developed for WhiteStar, which will be a larger heavier vehicle than the Roadster requiring more power, is a liquid-cooled motor. The Roadster will now also get a liquid-cooled motor. This will allow to produce more sustained power than before.
Getting power to the ground will be accomplished with a newly-developed single-speed transmission. The new unit is essentially a reduction gear. The new transmission is not based on any existing design and will be manufactured to Tesla's specifications. Major powertrain engineering consultancy Ricardo is assisting Tesla with transmission design. They are used to working with transmissions for high-powered cars having developed the gearboxes for the Bugatti Veyron and Ford GT, among many others. Components are currently be tested and a vehicle with a development version of DriveTrain 1.5 should be ready for testing next week.
Tesla is giving no time-line for when validation of the new hardware will be finished, but sometime later this year would be a likely target. In the mean time, series production of Roadsters with the interim single-speed transmission will begin on March 17, 2008 in England. Tesla has now received all necessary regulatory approvals to start selling cars and the first production model that was completed recently at the Lotus factory in Hethel has been crated up and will be shipped to the U.S. shortly. Once the new power-train has been validated, production will ramp up quickly and early units will be brought in to be retrofitted with new motors, transmissions and PEMs.
January 23rd, 2008
SOURCE: Tesla Motors
Tesla Motors Completes all Regulatory Approvals and Sets Schedule to Begin Production
First production 2008 Tesla Roadster Imported – Series Production Begins in March
• Tesla Motors has received all regulatory approvals to import the first production Tesla Roadster ("P1") for sale. This includes all necessary EPA and DOT approvals, including completion of all Federal Motor Vehicle Safety Standards (FMVSS.)
• P1 will arrive at Tesla Motors headquarters next week for delivery to customer Elon Musk, Chairman of Tesla Motors.
• Series production of the Tesla Roadster is scheduled to begin March 17th, 2008
• As communicated previously, early production units will be equipped with an interim transmission that meets durability requirements but limits acceleration to 5.7 seconds from 0 to 60 mph.
• Separately, Tesla Motors engineers have designed a permanent solution for mass production that supports the original specification of 0 to 60 mph in 4 seconds.
• The planned solution has some very positive benefits for our customers. Instead of a complex 2-speed transmission design, Tesla will achieve the original performance goals with a simpler one-speed unit mated to a higher rated Power Electronics Module (PEM.) The existing motor will be modified to have advanced cooling capabilities to handle the additional power. The permanent transmission unit will be engineered to handle the higher torque of the powertrain.
• The planned solution reduces program risk, provides better efficiency, lower weight, equal or better range, better thermal performance and quicker quarter mile acceleration due to the elimination of the need to shift gears.
• The planned solution incorporates the latest developments of our powertrain team which has been continually improving on Tesla's core technology.
• Early production will proceed at a limited rate and then ramp up to full production when the permanent powertrain solution is production ready later this year.
• The upgrade from the interim solution to the higher power, permanent solution will be provided to our customers free of charge when available later this year.