On Wed, 3 Mar 2010 09:47:35 -0600, "HeyBub"
wrote:

Don Klipstein wrote:

The thing that really stood out to me was the statement by Toyota's
president that they're going to look into programming a brake
override for the throttle.

I have only one question: WHY IN GOD'S NAME WAS THAT NOT THERE FROM
THE BEGINNING?

*Programming* a throttle override by the brake? As in relying on
lack of electronic malfunction in order to have the brake reliably
apply an override onto the throttle?


Heh! In a wonderful book called "Systemantics" the author discovered several
rules of systems. One of which was: "Fail Safe systems often fail by failing
to fail safe."

As an example, consider automotive braking:
* Originally, you stepped on a pedal which pulled a wire which activated the
brake shoes.
* Next stage was hydraulic brakes, with about twice as many parts that could
fail.

More parts that COULD fail, but a significantly lower probability that
ANY would. Having owned and driven vehicles with mechanical brakes I
can attest to the fact that "juice brakes" are infinitely more
reliable and effective.
* Then came power brakes with even more vulnerable parts.

Won't argue with you there - but again the incidence of power brake
failure is EXTREMELY low, as the system is dead-nuts simple.
* Next came dual brake systems.

Again - a HUGE increase in safety, because now you need at least 2
simultaneous failures to render the braking system inopperative.
* Then anti-lock brakes

A royal pain in the behind - trouble prone and un-necessary.
* Now we're back to "brake-by-wire" (although not the same wire as in
incarnation #1)

In between each of these "improvements" were dozens of minor tweaks. So,
then, today an automobiles braking system contains, oh, 100 times as many
parts at that of a Model-T.

No, not even a model T (which, by the way, had only brakes on the rear
wheels and the transmission.)
Even a 2 wheel braked car had more parts in each wheel than either a
hydraulic drum or disk brake when you count all the clevises, pins,
etc that were required - and EVERY ONE of them was critical.
Many juice drum brakes today have only 4 moving parts per wheel. 2
pistons and 2 shoes. The master cyl has 2 - the primary and secondary
piston..
It's MOVING parts that are critical because they wear, jam, and fail.


Both my '49 VW and my '28 Chevy had 4 wheel mechanical brakes.
The Chevy service brakes were external bands on the rear drum, and
internal shoes on the front - with internal shoes on the rear for the
emergency brake. To stop it from speed required yanking the handbrake
and stomping the pedal at the same time to keep from throwing the rear
drums out of shape.
The VW would go wherever it wanted when you first touched the brakes.

I carry a chain and a grappling hook.