Re: Production EVs

[Bob MacDowell <bobmacd@netcom.com>]

bdube@boulder.nist.gov (Bill Dube') writes:

>    I can easily lock up all four wheels on my Wabbit with the brakes. I
>can't stop the car from moving forward using the brakes even at part
>throttle if the car is in 2nd gear. If I put on the parking brake with both
>hands, the motor will turn the front wheels, and because there is more
>weight on the front wheels, the back wheels will be locked, but will drag
>forward, even at part throttle.

Hmm.

A brake's ability to brake is dependent on how much energy - rotation -
the brake sees.  The brake can dissipate a lot more energy at 10 mph
than it can at 0 mph (obviously).  And it can probably resist nearly
as much torque at 10 mph as at 0.  

In any case, the brake's torque is a much flatter curve than the motor's
torque, and at some point, they cross.  I'd guess they cross somewhere
around 10 mph.   That's the speed you'll be able to "hold" the EV to
using the brakes, for a few seconds, until the brakes overheat, at which
point you'll take off like a guided missile.  Hopefully before that the 
motor fails or you can find something big to safely collide with.

Of course that doesn't help in a lot of situations, like the crosswalk.

Any way you slice it, the publicity would SSSSUUUCCCCCCKKKKK. 
Could even result in regulation or prohibition of homebrew EVs.  

-Bob