Five Mile Beach weekly journal., 1915-04-16

QIner 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 ont
engine can run faster" than another.
The locomotive, although one of thu
simplest and best known of machines
embodies numerous devices o visible
to the eye Of the casual observer
which are most vital elements In it
efficiency and speed. For example
much of the power of the big expresI
engine depends upon the steam valvei
and the CRATES In the 6rebox quite al
much as it does upon the mere big
ness of the driving wheels. At tn.
same time it is true that large wheel
In ordinary fast running are a o
v%enience and In the very highesi
speeds a necessity. II becomes neces
sary. of course. to tighten the load al
the wheels are enlarged and increast
the speed. which introduces the sec
ond phase of the problem-the gratei
and heating surface.
Fast engines, to continue their worn
for a long time at a stretch. mus
make steam very rapidly. To accom-
plish this the heat of the fire mus
come In contact with the water at 1
great many points. A large >firebo1
Involves a CRATE of large area to admit
air TO the fire-a difficult matter sinci
but a small distance separates tn,
wheels. the width of the hrebox beint
thus limited. while the length mus
come within the limit to which thu
fireman can throw his coal.
A third factor Is the counterbalance
the solid filing fixed between th,
spokes of the driving wheels opposit,
the connecting rods. This is to balance
the weight of the cranks, parallel rod
and connections and, In addition. th'
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 a jerky motion.
However. us the influence of thu
weight is varied by the centrifugal
force. which, in turn. is greater or lesi
according as the speed is high or low
1t happens that a counterwelght which
is suitable at a speed or forty or fit,
miles an hour produces an injurious
pound on the rails at seventy-6v'
miles an hour.
1t follows. therefore, hat the weigh
must be heavier than the rods and con
nections because a part of its Office Il
to balance tie piston and other part
that slide horizontally and are unin
fuenced by centrifugal force. AS thu
speed increases the downward motion
of the weight. as that part of thi
wheel rolls over to the front, makes
the wheel with its load press dowT
upon the rail with so much more fore,
than it does when the weight is NOV
ing upward on the other side that tn,
effect upon the rail Is as II a heavy
blow were delivered upon it with I
hammer.
So to use an engine successfully al
the highest speed 1t is necessary t,
make the counterweight lighter thai
would be correct for moderate speeds
The light weights are not necessarily
dangerous Mt the lower speed, but theil
use would cause unnecessary wear and
tear on the engine and the track ant
IN some cases would even cause un
pleasant jerks upon the passenger
cars. For this reason fast engines arr
seldom built unless they can be used
In fast service all the time.
Properly proportioned valve open
ings are absolutely essential to a fas.
engine. These admit the steam to the
opposite ends Of the cylinder alter
nately. as the connecting rod move.
first forward and then backward, and
in a fast engine they must admit 4
large volume of steam very quickly
The valves must be moved so as frs
to open one passage and close the 9th
er and her as rapidly as possible close
the first and open the second.
1t will be noticed by eve the mos
casual observer that the opening tt
let the steam out of the cylinders int
TIE B~llOheSluCh Is St1 tIdt ltu1OS Us
large as that for admitting the live
steam. But even with this 1t requires
a considerable amount OF power t.
force the steam out with sufficient
quickness. This must be done in the
fraction Of a second.
There are many engines that can gel
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 IL
only In the way. 1t is this rapid ex
pulsion of tie dead" steam that makes
the vigorous putfs at the top of thu
chimney that seem to indicate thai
the locomotive is doing a tremendous
amount of work. 1t should be remem
bered. however. that this noise is moi
the result of real work. but only Of
this after operation. which engine