On Mar 24, 2015, at 2:55 PM, Lawrence Rhodes via EV <[email protected]> wrote:

> I'd like to run two mid sized motors.  One on each rear wheel.

That's a very ambitious design. You need a controller that can coordinate the 
power for each wheel to ensure the exact same amount of power on 
straight-and-level pavement, which is enough of a challenge...and then the 
controller needs to serve as a differential to vary the power and speed 
depending on direction of travel, side loading from aerodynamics, slick patches 
on the pavement on only one side, and so on.

Failure to do so can very easily result in a rather unstable vehicle prone to 
crashing.

And that's the sort of design whose computer programming would take a team of 
Tesla engineers a fair amount of time to come up with from scratch.

Much easier would be a single motor (or a pair of siamese motors if that's what 
gets you the power you need) connected to a traditional mechanical 
differential, with the axles connected to the differential. I'm sure there've 
got to be low-weight open differentials readily available that would be just 
fine for such an application.

> I want to build a skeleton and use cut plastic or Kevlar as body panels.

Kevlar? Seems an unusual choice of materials. Is this supposed to be a 
bulletproof Popemobile in addition to everything else?

If you're looking for something lightweight that's easy to shape, start with 
fiberglass for your prototypes and then carbon fiber when you know what you're 
doing.

If, on the other hand, you're planning on building this with flat 
panels...scratch your plans and start all over. The aerodynamics will eat you 
alive. Flat panels might be okay for a prototype for the chassis and drivetrain 
design, but you're going to need some serious aerodynamic engineering chops to 
get something in the power consumption range you're talking about. The design 
is going to have to resemble something from Burt Rutan far more than anything 
that's ever come out of Detroit.

And...skeleton and panels implies a frame design, which implies a lot of 
weight. You'll be much more successful with a monocoque design in which the 
body <i>is</i> the frame.

b&
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