Sixty freight cars have come roaring together over the mountains behind
Sam’s engine. But now the cars have to be separated. Some of them are
going to Baltimore. Some will turn north to Chicago. Others are bound
south. Freight cars for twenty different cities are coupled together in
one train, and somebody must unscramble them.
Suppose you have a lot of colored beads on a string and you want to
separate them into greens and reds and blues. The easiest way is to get
three cups and let the beads drop off one by one, each into its own cup
with the others of the same color.
That’s just what railroaders do with a freight train. Instead of cups,
of course, they have a lot of separate tracks, all branching off a main
track. On one branch track, they collect the cars that go to Baltimore;
on another, the cars for Chicago; on another, the cars headed south.
This system of tracks is a classification yard.
In order to turn the cars from one track to another, there must be a lot
of switches. A switch is made up of movable pieces of rail that guide
the cars’ wheels. Look at the picture and you will see how a switch
guides a car either along the main track or onto a branch track that
curves off to the right.
[Illustration]
[Illustration]
Some of the most wonderful inventions in the world have been put to work
in the big freight classification yards. First the regular engine leaves
the train and a special switch engine couples on. The engineer of the
switch engine has a radio telephone in the cab, so he can listen to
orders from the towerman who unscrambles the train.
The towerman sits in a tower beside the track at the top of a little
hill called the hump. The main track goes over the hump and down. Then
it divides into several branch tracks. If you uncouple a car just at the
top of the hump, it will roll down the slope by itself.
To make the car go onto the right branch, the towerman works an electric
switch. He just pushes little handles on the board in front of him, and
electric machinery moves the switches in the tracks.
On the desk beside him, the towerman has a list that tells him where
each car in the train is and what city it is headed for. He knows which
branch tracks should be used--track number 4 for cars going to
Baltimore, track 6 for Chicago cars.
[Illustration]
[Illustration: LOOKING OUT OF INSPECTOR’S PIT AT CAR PASSING OVERHEAD]
Slowly the switch engine pushes the train toward the hump. On the way
the cars pass over a big hole underneath the track. In the hole sits a
man in a chair that can be tipped and turned. And all around are bright
lights that shine on the undersides of cars as they pass. This is the
inspection pit. The man in the chair tilts this way and that, watching
through a shatterproof glass hood to see if anything is broken or loose
on the under side of the cars. When he spots a car that needs repairing,
he talks with the towerman by radio telephone. And the towerman switches
the car off to a repair track.
(Not all yards have radio telephone. In the ones that don’t, the
inspector pushes a button and squirts whitewash onto a car to mark it
for repair.)
Now the cars come close to the hump. A brakeman uncouples the first one.
Slowly it starts downhill. Then it gathers speed--faster, faster. If it
hits another car there will be a crash. But, like magic, something seems
to grab at the wheels and slow them down.
[Illustration: BRAKEMAN UNCOUPLING CARS]
Something does rise up like fingers from the sides of the track. It is
the car retarder which squeezes against the wheels and keeps the car
from rolling along too fast.
The retarder works by electricity. The towerman just presses a button or
a handle in the tower, and far down the track the retarder machinery
goes to work. Before railroads had this machinery, brakemen went over
the hump with the cars, working fast and hard to put the hand brakes on
at just the right time. Brakemen who did this were called hump riders.
Once in a while a hump rider still goes with a car of very fragile
freight that might be broken if it banged into another car the least bit
too hard.
[Illustration: LOOKING DOWN INTO PIT AT THE INSPECTOR AND HIS
SEARCHLIGHTS--]
Car after car drifts down the hump and stops just where it should. When
one freight train has been unscrambled, another rolls up beneath the
tower, and its cars, too, are shuffled. In just a few hours half a dozen
trains have been broken up and made into new ones.
Some yards have extra inspectors who stand on top of a building and look
down at the cars from above. They can see broken parts that the man in
the inspection pit might miss. In other yards, a man is stationed beside
the track that leads up to the hump. In his hands, he holds something
that looks like a gun. It is--an oil gun. As each car passes, he takes
aim and fires a stream of oil straight into the car’s journal box.
(You’ll read about the journal box on page 42.)
[Illustration]
Not every freight yard has a hump or car retarders or radio telephones.
Only the biggest ones have all these things. In many yards the switch
engine pushes the whole train first onto one track and then onto
another, dropping a car each time.
[Illustration: Diesel Switcher