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Re: Truck stopping distances?



Now I know to what the signs (NO Jake Brakes) on the Salinas peripheral roads
refer.

And: "........ I wonder if NASA
ever thought of using a big tailhook & strong cable on the runway?
They must have. Maybe the jerking would be too destructive to the
shuttle's airframe?

David Bowman

Superwomen ride the schuttle?

bc who can't believe the number of very big rigs that leave the cooling sheds
mornings in the world's largest producer of head lettuce.



"Andrew J. Graham" wrote:

Beating the dead horse :) , one must be careful in taking the analysis
too far if we're really trying to look at the real world here. When a
truck driver is faced with stopping a truck, especially if it is to be
done quickly, (not a panic stop, in which all beats are off), he doesn't
just apply the brakes and slow down. He also doesn't pump the brakes,
not because they're anti-lock, but because they're air-brakes. If you
pump air-brakes, especially on a downhill run, you're dead. But the
important factor being missed here if we're trying to look at what
*really* happens, the driver will downshift the transmission, forcing
the wheels to turn the motor at a higher rate than an idol, which
expends energy but not through the brakes. Another brake saver is a
noisy device called a "jake brake" which allows a diesel truck driver to
stop the exhaust valves from opening. This uses the forward motion of
the truck (through the tire/road contact, so it's still friction
dependent) to make the engine work against itself, expending energy
without using the brakes. The fact that it cuts down on brake
replacement is it's whole purpose. Jake brakes are very noisy (they
make a popping sound) and it is generally illegal to "pull" one within
city limits.

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