The Princeton union. [volume] (Princeton, Minn.) 1876-1976, 1915-03-11
RAILWAY ENGINES
Speed of Fast Locomotives and
How It Is Attained.
BIG WHEELS A NECESSITY.

But Equally Important Are the Steam
Valves, tho Crates In the Firebox and
the Ability to Make Steam Rapidly.
Other Vital Factors.
The average person thinks that the
bigger the locomotive and the greater
the diameter of its driving wheels the
faster 1t will go, and in the popular
mind these are the only reasons one
| engine can run faster" than another.
The locomotive, although one of the
simplest and best known of machines,
embodies numerous devices not visible
to the eye of the casual observer
which are most vital elements in its
efficiency and speed. For example,
much of the power of the big express
engine depends upon the steam valves
and the CRATES in the frebox quite as
much as it does upon the mere big
ness Of the driving wheels At the
same time it is true that large wheels
in ordinary fast running are a con-
venience and in the very highest
speeds a necessity. It becomes neces-
sary, of course, to tighten the load as
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 long time at, stretch, must
make steam very rapidly. To accom-
plish this the heat Of the fire must
come in contact with the water at
great many points. A large firebox
involves crate of large area to admit
air to the fre-a difficult matter since
but small distance separates the
wheels, the width of the firebox being
thus limited, while the length must
come within the limit to which the
fireman can throw his coal.
A third factor is the counterbalance,
the solid filling fixed between the
| spokes of the driving wheels opposite
the connecting rods. This is to balance
the weight of the cranks, parallel rods
and connections and, in 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 a jerky motion.
However, as the influence Of the
| weight is varied by the centrifugal
force, which, in turn, is greater or less
according as the speed is high or low,
it happens that counterweight which
is suitable at speed or forty or fifty
| miles an hour produces an injurious
! pound" on the rails at seventy five
! miles an hour.
It follows, therefore, that the weight
must be heavier than the rods and con-
nectons because a part Of its Office is
| to balance the piston and other parts
| that slide horizontally and are unin-
fluenced 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 50 much more force
| than it does when the weight is NOV
ing upward on the other side that the
| effect upon the rail is as If a heavy
blow were delivered upon it with
| hammer
So to use an engine successfully at
the highest speed it 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 I'M
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 a fast engine they must admit a
| 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 Give"
steam. But even with this it requires
a considerable amount of power to
force the steam out with sufficient
quickness. This must be done in the
fraction of a 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. It 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