As we continue the tale of Elon and Martin, we pick up from the initial involvement of Elon Musk in Tesla Motors. Musk has put in the single largest chunk of money that has allowed Tesla to develop and now start building an electric car. Here we delve into the subject of his role in design decisions. As some in the mainstream media have taken to referring to Musk as the "creator" of the Tesla Roadster, this is a particularly contentious subject.

The whole issue of the choice of transmission suppliers is a particularly thorny one. Musk was insistent that Tesla should build a car worthy of the price tag. Anyone who has ever worked in the auto industry knows that is almost always a lot harder than it looks. The friction that clearly existed between Eberhard and Musk from very early on in their relationship definitely didn't help matters. (Note:If you missed Part 1 check it out first).

ABG: So, how did you get to the first stage, of the Roadster, the specs that debuted in 2006 with the first prototypes? How did that come about?

Read on after the jump.

JB Straubel, Chief Technical Officer at Tesla Motors has just put up a new post at the Tesla Blog with an extensive update on the Roadster drivetrain updates that are coming later this year. As we reported at Tesla's recent schedule update, the Silicon Valley start up is currently planning a running change to the upgraded powertrain beginning with car #41 which should happen sometime in late summer. There aren't any huge surprises in Straubel's post, but there are some interesting details. When Tesla first told us about their plans for the 1.5 back in January, the plan was to modify the power electronics module to be able to supply more current to the motor thus increasing the output to a level that would allow meeting the vehicle performance targets without having to use a two speed gearbox.

Generally, pumping more current through an electrical circuit has the negative side effect of generating a lot more heat as the resistance increases. The indication we were given at the time was that the cooling capability of the motor would be increased to help dissipate that heat. Based on Straubel's description of the changes, it looks like they took a different approach instead, one that is all too uncommon in the auto industry. Instead of applying a band-aid and treating the heat symptom by adding cooling capacity, they chose to attack the disease itself. In electrical circuits heat is caused by resistance to current flow. Resistance is the electrical analog of mechanical friction. The more electrons you try to push against resistance in circuits the more heat you generate. Continue reading after the jump.

The chief technical officer at Tesla Motors tells AutoblogGreen that 10 to 15 more test prototypes will be built next month as the company prepares to start manufacturing the much talked-about electric roadster in mid-2007. "We'll be finalizing the last changes we want to make from the first batch to the second," says JB Straubel, who was promoting the Tesla Roadster at the LA Auto Show. The first 10 prototypes are currently undergoing a variety of durability and validation tests around the world. "We're almost at the 50-yard line in our crash testing," adds Straubel, noting that the engineering team continues to make minor improvements as results are evaluated. "We've finalized all the major engineering decisions. From 10 feet you wouldn't recognize any changes that will be in the final production version."

Straubel, an electronics wizard who rebuilt a salvaged golf cart before he had his first car, says he doesn't see a major leap in battery technology in the near future and is skeptical of such claims circulating the industry. "People love to latch on to this great next idea but historically that's not how it happens. The reliable, tested technology gets better one step at a time." Straubel says low-cost performance batteries are holding back the development of retro electric conversions on existing vehicles. "There are hundreds, maybe thousands, who are very interested and will continue to convert all sorts of cars. The challenge is, where do you find a good drive system? Where do you get a high-performance battery? I think people will continue to convert to electric vehicles but they'll be shorter range and lower performance."

Related:

• EDTA Conference: Tesla Motors ready to license battery tech to other companies
• Tesla Roadster unveiled in Santa Monica