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Posted by Androcles on June 5, 2009, 10:35 pm

> tgdenn...@earthlink.net wrote:
> >> On 6/5/09 1:26 PM, in article
> >> o6idnVqzaun2_rTXnZ2dnUVZ_gJi4...@giganews.com,
> >>>> Again you've lost me---you are obviously misinterpreting what I said.
> >>>> Braking is done by the electric motor; for most of the braking period
> >>>> you are recovering the kinetic energy, which is why it is called
> >>>> regenerative braking. The ultimate implementation would have no disc
> >>>> brakes at all. If you need further explanation please let me know.
> >>> Motor/generators are transducers, not brakes. That means you can only
> >>> slow down, not come to a complete stop. If the electronic controller
> >>> failed, you couldn't even slow down. How big a market do you expect
> >>> for
> >>> cars without brakes?
> >> True. Thanks for the affirmation, Bill.
> > But motors can be reversed, and so you can certainly come to a
> > complete stop using only the motors. However, as I said, there can be
> > a simple type of brake, since you need something for parking.
> No they cannot! Not in real world applications! Try it! Try using only
> engine braking. Engine braking has far more stopping potential than an
> electric motor. But it still is far from enough!

I think maybe you are not reading carefully and just overreacting. I
said that electric motors can be reversed, which means that they have
as much 'stopping potential' as they have starting potential.

============================================
Yep, if you can spin the wheels at start up then you can apply
the same torque stopping them. However, braking does a better
job in an emergency because most brakes can lock the wheels
even when the motive power is insufficient to spin the wheels at
startup.

> > But the advantage of regenerative braking with four motors is that you
> > get smooth ABS when it matters----going from fast to very slow. You
> > *don't* need high-quality disc brakes---you could have a drum operated
> > by cable.
> You are wrong, and now I understand that your automotive engineering
> knowledge is just sheer impressionism.

No, I'm not wrong. Regenerative braking is a real effect, and with a
smart controller you will avoid losing traction.

I'm not saying it is a trivial matter to set up such a system but
there's nothing that prohibits it.
============================================
It's as simple as it can be, actually. The back-emf that the motor
generates limits the current and if you drive the motor faster
through the shaft the current reverses, which is exactly what you
want to recharge a battery.
You do not need to reverse the direction of the motor.
For a vehicle the energy losses are overcoming air resistance
and bearing/gearbox friction. Any braking is an additional loss
as heat which cannot be recovered.


>Oh, and cables stretch which is
> why Volkswagen abandoned cable-actuated brakes in 1953. Catch up.

There are cables and there are cables. And we are not exerting tons of
force in this application.

-tg
===============================================
You seem to be trying to educate a complete idiot. Good luck!



> > I certainly understand that many of us would be nervous about driving
> > the first generation of completely brake-free cars,
> Corvettes, and my builds, use fly-by-wire for throttle. No problem.
> Catch up.




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