Aberdeen herald. [volume] (Aberdeen, Chehalis County, W.T.) 1886-1917, 1915-03-30
RAILWAY ENGINES
Speed Of Fast Locomotives and
How Il Is Attained.
BIG WHEELS A NECESSITY.

the Ability ta Make Steam Rapidly.
Other Vital FAotors.
The average person thinks that the
bigger the locomotive ana the greater
the diameter OF its driving wheels the
faster 1t win 20. and In the popular
mind these nIV the only reasons one
engine Gun run faster" than another.
The locomotive. although one Of the
and best known Of machines,
cmbodies numerous devices not visible
to tho eye of the casual observer
which are most vital elements In it,
efficiency and speed. For example.
much of the power Of the big express
engine depends upon the steam valves
and the CRATES In the nrebox quite a.
much 40 It does upon the mere big
ness Of the driving wheels. At the
same time It IL true that large wheels
in ordinary fast running are con-
vcnience aud In the very highest
speeds a necessity. It becomes neces-
sary, Of course. to tighten the load -
the wheels are enlarged and increase
the speed. which introduces the sec'
ond phase Of the problem-the crates
and heating surface.
Fast engines, to continue their work
for Z long time at q stretch. must
make steam very rapidly. To accom-
plish this the heat Of the dre must
come in contact with the water at q
great many points. A large flrebox
involves CRATE Of large area to admit
air to the 6re-a didicult matter since
but a small distance separates the
wheels. the width Of the nrebox being
thus limited, while the length must
come within the limit to which the
fireman can throw his coal. r. ~.
A third factor Is the counterbalance.
the solid filflnY fxed between the
spokes Of the driving. wheels opposite
the connecting rods. This y to balance
the weight Of the cranks; parallel rods
and connections and, 10 addition, the
force on the wheels Of the weight
of the moving piston In the cylinder.
Lacking this balance the wheels would
roll too rapidly when the rods and con-
nections were moving downward and
too slowly when they were moving up
ward, thus causing Jerky motion.
However, as the influence Of the
weight is varied by the centrifugal
force. which. in turn, is greater or less
according rs the speed is high or low.
1t happens that counterweight which
Is suitable at a speed or forty or fifty
miles an hour produces an injurious
pound" on the rails at seventy-fve
miles an hour.
It follows, therefore, that the weight
must be heavier than the rods and con-
nections because part Of its Office is
to balance the piston and other parts
that slide horizontally and are unin-
luenced by centrifugal force. As the
speed increases the downward motion
of the weight, as that part Of the
wheel rolls over to the front, makes
the wheel with its load press down
upon the rail with 90 much, more force
than It does when the weight IL NOV.
ing upward on the other side that the
effect upon the rail Is as II heavy
blow were delivered upon It with a
hammer.
SO to use an engine successfully at
the highest speed 1t is necessary to
make the counterweight lighter than
would be correct for moderate speeds.
The light weights are not necessarily
dangerous at the lower speed, but their
use would cause unnecessary wear and
tear on the engine and the track and
in some cases would even cause un-
pleasant jerks upon the passenger
cars. For this reason fast engines are
seldom built unless they can be used
in fast service all the time.
Properly proportioned valve open
ings are absolutely essential to fast
engine. These admit the steam to the
opposite ends Of the cylinder alter
nately, as the connecting rod moves
first forward and then backward, and
in fast engine they must admit
large volume of steam very quickly
The valves must be moved SO as first
to open one passage and close the 9th.
er and then as rapidly as possible close
the first and open the second.
1t will be noticed by even the most
casual observer that the opening to
let the steam out of the cylinders into
the smokestack is several times as
large as that for admitting the live"
steam. But even with this 1t requires
a considerable amount of power to
force the steam out with sufficient
quickness. This must be done in the
fraction Of second.
There are many engines that can get
steam into the cylinders quickly
enough and that are otherwise all
right for high speed, but which are
not so arranged to get rid of this
steam which has been used and is
only in the way. 1t is this rapid ex-
pulsion Of the dead" steam that makes
the vigorous puffs at the top Of the
chimney that seem to indicate that
the locomotive is doing tremendous
amount Of work. 1t should be remem.
bered, however, that this noise Il not
the result Of real work, but only Of
this after operation. which engine
builders would avoid. There II class
Of locomotives, those arranged on the
compound system" in which the pufts
are 10 faint that the engine would
seem to be doing nothing at an
Warrington Star.
No pain, no palm; NO thorns, no
throne: M eall NO glory: NO cross. mn