The Democratic banner. (Mt. Vernon, Ohio) 1898-192?, 1915-04-13
RAILWAY ENGINES
Speed of Fast Locomotives and
How II Is Attained.
BIG WHEELS A NECESSITY.

VeVee, tno 0TAtos IN the F"oo~1 ~"A
the Ability to Make Steam Rapidly.
Other Vital Factors.
The aveyage 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 f1rebox quite as
much as it does upon the mere big
ness Of the driving wheels at the
same time 1t Is true that large wheels
In ordinary fast running are con
venience and in the very highest
speeds necessity. 1t 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 o
great many points. A large firebOx
involves a crate of large area to admit
air to the fre--a difficult matter since
but a small distance separates the
wheels, the width of the f1rebOx 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 cranlis, parallel rods
| force on the wheels Of the weigh
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 as the speed is high or low
1t happens that counterwelght which
II 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
nections because part of its office Il
to balance the piston and other part,
that slide horizontally and are unin
duenced by centrifugal force. As thu
speed increases the downward motor
Of the weight, a. that part Of th'
wheel rolls over to the front, make
the wheel with its load press dow
upon the rail with 80 much more fore
than It does when the weight is NOV
ing upward on the other side that tn
effect upon tho rail Is as II a heavl
blow were delivered upon It with |
hammer.
SO to use an engine successfully a
the highest speed 1t is necessary +
make the cOunterweight lighter thai
would be correct for moderate speeds
The light weights are not necessarily
dangerous at the lower speed, but thei
use would cause unnecessary wear an
tear on the engine and the track an
In some cases would even cause ur
pleasant Jerks upon the passenge
cars. For this reason fast engines ar
seldom built unless they can be use
In fast service all the time.
Properly proportioned valve oper
ings are absolutely essential to fas
engine. These admit the steam to tn
opposite ends of the cylinder altel
na.ely, as the connecting rod move
first forward and then backward, an
in a fast engine they must admit
large volume of steam very quickl!
The valves must be moved SO as frs
to open one passage and close the otl
er and then as rapidly as possible clos
the first and open the second.
1t will be noticed by even the moi
casual observer that the opening
let the steam out Of the cylinders int
the smokestack Is several times a
large as that for admitting the "live
steam. But even with this 1t require
a considerable amount Of power
force the steam out with sufficieI
Quickness. This must be done In Il
fraction Of a second.
There arc many engines that can g
steam into the cylinders quick
enough and that are otherwise a
y right for high speed. but which a
l. not 10 arranged to get nd OF tn
/. steam which has been used and
9 only in the way. II II this rapid e.
a pulsion Of the dead" steam that make
!. the vigorous puffs at the top OF Il
chimney that seem to indicate th'
the locomotive is doing a tremendo'
amount of work. 1t should be remer
. bered, however, that this noise Ia n
the result of real work, but only