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[Illustration:
_Frontispiece._] KINSUA VIADUCT, ERIE RAILWAY, U.S.A. [_See p. 97._]
_LONGMANS’ CIVIL ENGINEERING SERIES_
RAILWAY CONSTRUCTION
BY
WILLIAM HEMINGWAY MILLS, M.INST.C.E.
PAST PRESIDENT OF THE INSTITUTION OF CIVIL ENGINEERS OF IRELAND, AND
ENGINEER-IN-CHIEF OF THE GREAT NORTHERN
RAILWAY OF IRELAND
[Illustration]
_WITH ILLUSTRATIONS_
FOURTH IMPRESSION
LONGMANS, GREEN, AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK, BOMBAY, AND CALCUTTA
1910
_All rights reserved_
PREFACE
The construction and maintenance of a railway calls for the
application of so many branches of engineering that several volumes
would be required to do ample justice to a subject so comprehensive
and ever-extending. To avoid attempting so wide a range, the object of
the following pages has been to describe briefly some of the
recognized leading features which regulate railway construction, and
to assist the explanation with sketches of works selected from actual
practice.
Where the number of existing good examples is legion, it is somewhat
difficult to make a choice for illustration, and the course adopted
has been to select such samples of structures as appear best to
elucidate in a simple manner the different types of work under
consideration.
In the drawings and diagrams many important minor details are
necessarily omitted, partly to avoid complexity, but principally to
leave more prominent the leading features of the particular piece of
work referred to in the description. Some of the sketches of the large
span bridges and large span roofs are only shown in outline; but, as
their principal dimensions are given, a general idea can be obtained
of their actual proportions.
No allusion is made to the requisite strengths of the various
structures described, nor to the necessary dimensions of the materials
used in their construction, as this would necessitate the introduction
of a vast amount of mathematical formulæ which does not come under the
province of the object in view, and which the engineer has already at
command from his training and works of reference.
Neither is any mention made as to the probable cost of the different
works of construction, as these must always vary to a very large
extent, according to the locality, facility of supply, and current
prices of materials.
Every railway scheme which is the outcome of public enterprise has its
commercial aspect and influence. The large sums to be invested in its
construction are expected to yield permanent and increasing returns,
and this desirable end can only be attained where there is thorough
efficiency in works and equipment, and a full compliance with those
national regulations which control matters connected with public
safety. The correct dealing with the technical requirements and
structural features of the undertaking must always precede all other
considerations, as the constituted authorities will exact a proper
fulfilment of all the statutory obligations, regardless of the
prospective remuneration to the promoters. A stroke of the pen may
change a train-service, or alter the rates and tariffs, but a
modification in the works of construction arising out of errors or
oversight, would entail a heavy expenditure and tedious delay. The
essential point of every railway undertaking must be its suitability
and completeness in every respect for the duty for which it is
intended.
Notes of what has been done are always valuable for consideration and
comparison, and that the following brief description and sketches may
be found useful for reference, is the earnest wish of the writer.
W. H. MILLS,
M.INST.C.E.
CONTENTS
CHAPTER I.
PAGE
Location of a line of railway--Government regulations--Questions
for consideration in connection with gauge, gradients, and
curves 1
CHAPTER II.
Works of construction: Earthworks, Culverts, Bridges,
Foundations, Screw piles, Cylinders, Caissons, Retaining
walls, and Tunnels 60
CHAPTER III.
Permanent way--Rails--Sleepers--Fastenings--and Permanent-way
laying 182
CHAPTER IV.
Stations: Station Buildings, Roofs, Lines, and Sidings 248
CHAPTER V.
Sorting-sidings--Turn-tables--Traversers--Water-Tanks and
Water-Columns 285
CHAPTER VI.
Comparative Weights of some Types of Modern Locomotives 304
CHAPTER VII.
Signals--Interlocking--Block Telegraph and Electric Train
Staff Instruments 313
CHAPTER VIII.
Railways of different ranks--Progressive improvements--Growing
tendency for increased speeds, with corresponding increase in
weight of permanent way and rolling-stock--Electricity as a
motive-power 348
INDEX 361
CHAPTER I. 1
Location of a line of railway--Government regulations--Questions
for consideration in connection with gauge, gradients, and
curves.
Location.--The locating of a line of railway, or the determination
of its exact route, is influenced by many circumstances. In a rich
country, with thickly populated districts and large industrial
enterprises, there are towns to be served, manufacturing centres to be
accommodated, and harbours to be brought into connection; while, at
the same time, there may be important estates which must be avoided
and private properties which must not be entered. Each point will
present its own individual claim for consideration when selecting the
route which promises the greatest amount of public convenience and
commercial success.
In new countries--in our colonies, and especially out in the far west
of Canada and the United States--railways have to be laid out in
almost uninhabited districts, where there is but little population or
commerce to serve, and where the principal object is to obtain the
best and most direct route through the vast territories, leaving
colonists and settlers to choose afterwards the most convenient sites
for towns and villages. Untrammelled by the network of public and
private roads and properties which are met with at home, it might
appear that the locating of such a line would be comparatively light;
but even in such countries, which at first sight seem to present
unlimited freedom for selecting a route, much can be done, and should
be done, by taking a course through those plains and districts which
possess the best natural resources for future agricultural,
manufacturing, or mineral development.
In addition to the motives of convenience and policy, the route of
every line of railway must be influenced by the natural features of
the country--the mountains, valleys, and rivers. These physical
obstacles are in some cases on such an enormous scale as to compel 2
long detours in the formation of a more suitable opening; and in
others, although the difficulties are not insurmountable, they may
involve works of great magnitude and expense.
In a comparatively rich country, with a prospect of large and
remunerative traffic, a succession of heavy works, bridges, and
tunnels may be admissible and expedient; but in new countries economy
of outlay has to be considered, and costly works avoided as much as
possible.
Every one of the heavy works on a line, whether lofty bridges, long
viaducts, or costly tunnels, not only enormously increase the original
expenditure of the undertaking, but also entail large annual outlay in
the necessary constant supervision and maintenance.
Each particular scheme will have to be discussed on its own individual
merits. The heavy, high-speed passenger traffic line will suggest
light gradients and easy curves, while on secondary lines and in
thinly populated districts it may be prudent, for the sake of economy,
to introduce sharper curves and heavier gradients. Even in the latter
case, and especially in new countries, it is well to keep in view the
future possibilities of the undertaking. The steeper the gradients,
the greater the cost and time in working the traffic, and if there is
every probability of early and large development, the prospective
increase may warrant an additional outlay in the original
construction.
Large, open plains and wide valleys of important rivers generally
afford ample latitude for the selection of a suitable route, and, by
taking advantage of the gradations of altitude, a favourable course
may be adopted without incurring excessive gradients. When traversing
moderately hilly districts, some low ridge or opening may be found,
which may form a pass from the one side to the other, and the line may
be laid out for a long distance to lead gradually up to the highest
point. But when a route has to be laid out over some of those lofty
mountain ranges which are met with abroad, the locating of a suitable
line, or of any line, becomes particularly intricate and difficult. A
comparatively low ridge may be found possessing features in favour of
the project, but the question will be how to reach that point. The
nearer the summit of these high mountains, the more precipitous the
sides; no one slope can be found sufficiently long and uniform to 3
permit a practical direct ascent, and the only way out of the
difficulty is to make a series of detours along the various spurs of
the mountains to gain length to overcome the height. Each detour has
to be the subject of most careful study. Forming part of a long series
of ascending gradients, it has to follow the winding of the
mountain-side, must be laid out to be always gaining in height, and
will comprise important works, many of them of considerable extent,
necessary for protection against the floods and atmospherical changes
of the locality.
In these higher altitudes nature is met with on the grandest and most
rugged scale. Deep gorges, wide ravines, and almost perpendicular
rocks form the pathway along which the line must be carried, and the
skill of the engineer is taxed to the utmost to select a course which
shall comprise a minimum of the works of magnitude. Mile after mile of
line must be laid out in almost inaccessible places, loose or broken
rocks must be avoided, a firm foundation must be obtained at all
points skirting high ledges, and ample provision must be made for
those mountain torrents which rise so suddenly, and are liable to
sweep away all before them.
Many grand examples of these detour lines are in existence in
different parts of the world, and the traveller passing over them can
realize the difficulties that had to be encountered, and the masterly
manner in which they have been overcome.
Before proceeding to carry out the works of any line of railway, it is
necessary to prepare a complete plan and section of the line, showing
the route to be followed and the position of the various curves,
gradients, and principal works. Within certain limits, the course of
the line may have to be slightly modified as the work proceeds, in
consequence of ground turning out unfavourable, river-crossings
treacherous, or of sites involving so many contingent alterations that
it is found better to avoid them altogether. The route should,
however, be so carefully studied out before completing the final plan
and section, as to leave only minor deviations of line and level to be
dealt with in the actual carrying out of the work.
The promoters of lines in the United Kingdom obtain valuable
assistance from the ordnance maps, which give full and reliable
information regarding the position of all roads, rivers, and
boundaries of counties, parishes, and townlands. In many parts abroad 4
local maps are scarce, and not always accurate, and engineers have to
depend principally on their own surveys, and rely upon the resident
local authorities for any particulars as to divisions of territory. On
some of our great colonial plains, and out in the far west of America,
a line may be laid out for miles without a single landmark to localize
it on a plan; but careful setting out, and the relative levels of the
ground and gradients, as shown on the section, will always indicate
the correct position of any portion of the work.
Both at home and abroad complete plans and sections of any proposed
railway must be deposited with the proper Government authorities, and
must be approved and sanctioned by them before permission can be
obtained to proceed with the works.
The regulations regarding the scale and general arrangement of these
plans and sections vary in different countries, and are subject to
modification from time to time.
Each country has its own special enactments relative to the method of
dealing with roads, rivers, streams, and public and private property
proposed to be interfered with in the construction of any line, and a
knowledge of these is absolutely necessary for the promoters of any
new scheme, inasmuch as some of the requirements may, in certain
instances, influence the precise route to be selected.
The English Government has passed several Acts of Parliament setting
forth the general conditions which must be complied with in the
construction of any railway in the United Kingdom. These conditions,
or standing orders, relate both to the acquirement of land and
property, the size and description of works for public or private
accommodation, and the inspection and official approval of the
undertaking when completed. These fixed regulations are alike valuable
to the promoters and to the public; the former are informed of the
principal points with which the scheme must conform, and the latter
know the limit of their legal demands.
No line of railway, or extension of any railway, will obtain
Parliamentary sanction unless it can be satisfactorily proved in the
outset, that its construction would be of public advantage. This point
is of paramount importance, and due weight must be given to it when
preparing to refute the evidence of opponents to the scheme.
[Illustration: Fig. 1.]
When conceding the right to make any railway, Parliament grants with 6
it the power to purchase lands or property compulsorily, or by
agreement, to change and divert roads and streams in the manner shown
on the deposited plans, and to construct all necessary bridges and
works in accordance with the standing orders, or such modifications of
them as may be approved by the Board of Trade.
The standing orders, or Government regulations, are very
comprehensive, and include much detailed information on all questions
likely to arise. The following brief summary of some of the principal
orders relating to deposited plans, and works of construction, will be
found useful for reference.
Extract from Government Standing Orders and Regulations.--All
plans and sections relative to proposed new railways must be lodged
with the constituted Government Authorities on or before November 30.
Every deposited plan must be drawn to a scale of not less than four
inches to a mile, and must describe the centre line, or situation of
the work (no alternative line being allowed), and must show all lands,
gardens, or buildings within the limits of deviation, each one being
numbered with a reference number, and where powers to make lateral
deviations are applied for, the limits of such deviation must be
marked on the plan.
Unless the whole of such plan be drawn to a scale of not less than 400
feet to an inch, an enlarged plan must be drawn to that scale of every
building and garden within the limits of deviation.
The Railway Clauses Act limits the extent of deviation to 100 yards on
each side of the centre line in the country, and 10 yards on each side
of the centre line in towns or villages.
The distances must be marked on the plan in miles and furlongs from
one of the termini.
The radius of every curve not exceeding one mile must be marked on the
plan in furlongs and chains.
In tunnels the centre line must be dotted, but no work must be shown
as tunnelling, in the making of which it is necessary to cut through,
or remove the surface soil. If it is intended to divert or alter any
public road, navigable river, canal, or railway, the course and extent
of such diversion, etc., shall be marked on the plan.
[Illustration: Fig. 2.]
When a railway is to form a junction with an existing railway, the 8
course of such existing railway must be shown on the plan for a
distance of 800 yards on each side of the proposed junction. In the
case of Bills for constructing subways, the plans and sections must
indicate the height and width of such subway, and the nature of the
approaches by which it is proposed to afford access to such subway.
The Book of Reference must contain the names of all owners, lessees,
and occupiers of all lands and houses of every parish within the
limits of deviation.
The numbers on the Book of Reference must correspond with the numbers
on the plan, and opposite to each number must be entered a brief
description of the property, whether field, garden, house, road,
railway, or river. It is intended that the plan and Book of Reference
together, shall afford ample information to enable all parties
interested to ascertain to what extent their property will be affected
by the proposed undertaking.
The section must be drawn to the same horizontal scale as the plan,
and to a vertical scale of not less than 100 feet to an inch, and must
show the level of the ground, the level of the proposed work, the
height of every embankment, the depth of every cutting, and a
horizontal datum line which shall be referred to some fixed point,
near one of the termini.
In every section of a railway, the line of railway marked thereon must
correspond with the upper surface of the rails.
Distances on the datum line must be marked in miles and furlongs to
correspond with those on the plan; a vertical measure from the datum
line to the line of the railway must be marked in feet and decimals at
the commencement and termination of the railway, and at each change of
gradient, and the rate of inclination between such vertical measures
must also be marked.
Wherever the line of railway crosses any public carriage road,
navigable river, canal, or railway, the height of the railway over, or
depth beneath the surface thereof, and the height and span of every
arch by which the railway will be carried over the same, must be
marked in figures.
[Illustration: Fig. 3.]
In the case of a public road level crossing, it must be described on
the section, and it must also be stated if such level will be
unaltered. If any alteration be intended in the level of any canal,
public road, or railway which will be crossed by the intended line of
railway, the same must be stated on the section and cross-sections to
a horizontal scale of not less than 330 feet to an inch, and a vertical 10
scale of not less than 40 feet to an inch must be added, which must
show the present surface of such road, canal, etc., and the intended
surface thereof when altered, and the greatest of the present and
intended rates of inclination marked in figures, such cross-sections
to extend 200 yards on each side of the centre line of railway.
Wherever the height of any embankment, or depth of any cutting, shall
exceed 5 feet, the extreme height over or depth beneath the surface of
the ground must be marked in figures upon the section.
All tunnels and viaducts must be shown on the section.
At a junction with an existing railway, the gradient of such existing
railway must be shown on the section on the same scale as the general
section for a distance of 800 yards on each side of the point of
junction.
Where the level of any turnpike or public road has to be altered in
making any railway, the gradient of any altered road need not be
better than the mean inclination of the existing road within a
distance of 250 yards of the point of crossing the railway; but where
the existing roads have easy gradients, then the gradients of the
altered roads, whether carried over, or under, or on the level with
the railway, must not be steeper than 1 in 30 for a turnpike road, 1
in 20 for a public carriage road, 1 in 16 for a private or occupation
road.
A good and sufficient fence, 4 feet high at least, shall be made on
each side of every bridge, and fences 3 feet high on the approaches.
The application to cross any public road on the level must be reported
upon by one of the officers of the Board of Trade, and special
permission for the work must be embodied in the Act.
Not more than 20 houses of the labouring classes may be purchased in
any city or parish in England, Scotland, and Wales, or more than 10
such houses in Ireland, until approval has been obtained to a scheme
for building such houses in lieu thereof as the authorities may deem
necessary.
Every bridge (unless specially authorized to be otherwise) must
conform with the following regulations:--
A bridge over a turnpike road must have a clear span of 35 feet on the
square between the abutments, with a headway, or height, of 16 feet
for a width of 12 feet, as shown on Fig. 12.
[Illustration: Fig. 4.]
A bridge over a public road must have a clear span of 25 feet on the 12
square between the abutments, with a headway of 15 feet for a width of
10 feet, as shown on Fig. 13.
A bridge over a private or occupation road must have a clear span of
12 feet on the square between the abutments, with a headway of 14 feet
for a width of 9 feet, as shown on Fig. 14.
Road bridges over the railway must have the same clear width between
the parapets, measured on the square, as the widths prescribed for
road bridges under the railway, or 35 feet for a turnpike road, 25
feet for a public road, and 12 feet for private or occupation road.
It is not compulsory, however, to construct the public road bridges
over or under the railway of a greater width than the average
available width of the existing roads within 50 yards of the point of
crossing the railway, but in no case must a bridge have a less width
than 20 feet. Should the narrow roads be widened at any future time,
the railway company will be under the obligation to widen the bridges
at their own expense to the extent of the statutory widths of 35 feet
for a turnpike road, and 25 feet for a public road.
Suitable accommodation works in the form of bridges, level crossings,
gates, or other works, must be provided for the owners, or occupiers
of lands, or properties intersected or affected by the construction of
the railway; or payments may be made by agreement instead of
accommodation works. All questions, or differences between the Railway
Company, and the owners or occupiers of property affected, will be
decided by the authorities duly appointed by the Government for the
purpose.
In constructing the railway, the Parliamentary plans and sections may
be deviated from to the following extent:--
The centre line may be deviated anywhere within the limits of
deviation (100 yards on each side of the centre line in country, and
10 yards each side in towns, or villages).
Curves may be sharpened up to half a mile radius, and further, if
authorized by the Board of Trade.
A tunnel may be made instead of a cutting, and a viaduct instead of an
embankment, if authorized by the Board of Trade.
The levels may be deviated from to the extent of 5 feet in the
country, and 2 feet in a town, or village, and various authorities
have power to consent to further deviations.
[Illustration: Fig. 5.]
Gradients may be diminished to any extent, gradients flatter than 1 in
100 may be made steeper to the extent of 10 feet in a mile, and 14
gradients steeper than 1 in 100 may be made steeper to the extent of 3
feet in a mile, or to such further extent as may be authorized by the
Board of Trade.
Suitable fences must be erected on each side of the line, to separate
the land taken for the use of the railway from the adjoining lands not
taken, and to protect such lands from trespass, or the cattle of the
owners, or occupiers thereof from straying on to the railway.
In addition to the Parliamentary plans, and sections, and Book of
Reference, an estimate of the cost of each separate line, or branch,
must be prepared as near to the following form as circumstances will
permit.
ESTIMATE OF THE PROPOSED (RAILWAY).
Line No._______
------------------------------------------+-----------------------------
Miles. F. Chs. | Whether single or double.
Length of Line: ____ ____ ____ | _______________________
-----------------------+--------------+---+------+-----------+----------
| Cubic yards. | Price per | £ _s. d._ | £ _s. d._
| | yard. | |
+--------------+-----------+-----------+---------
Earthworks:-- | | | |
Cuttings--Rock | | | |
Soft soil | | | |
Roads | | | |
+--------------+-----------+-----------+
Total | | | |
+--------------+-----------+-----------+
|
Embankments, including roads, ____ cubic yards |
Bridges, public roads--number |
Accommodation bridges and works |
Viaducts |
Culverts and drains |
Metallings of roads and level crossings |
Gatekeepers’ houses at level crossings |
Permanent way, including fencing:-- |
|
Miles. F. Chs. | Cost per mile. |
| £ _s._ _d._ |
____ ____ ____ at | ____ ____ ____ |
|
Permanent way for sidings, and cost of junctions |
Stations |
+---------
Contingencies ____ per cent. |
+---------
A. R. P. |
Land and buildings ____ ____ ____ |
+---------
Total £ |
+=========
Dated this _______ day of ______________________ 18____
Witness: __________________________
___________________________________
Engineer.
[Illustration: Fig. 6.]
The same details for each branch, and general summary of total cost. 16
Every Railway Bill must be read twice, both in the House of Commons
and in the House of Lords. A committee, duly appointed for each House,
must report upon it, and if the reports from such committees be
favourable, the Bill will be read a third time, and passed.
When it has passed both Houses, the Bill receives the Royal Assent,
and becomes law.
The minimum scale of four inches to a mile for the plans is so very
small that it is rarely, if ever, adopted. It would necessitate
enlarged plans of so many portions to show clearly the property or
buildings inside the limits of deviation, that in practice it is found
expedient to make the plans to a much larger scale.
Figs. 1 and 2 show a small portion of a Parliamentary plan and section
drawn to the minimum scale allowed, with an enlargement of a small
part to distinguish the houses clearly.
Figs. 3 and 4 show a part of the same plan and section drawn to a
scale of 400 feet to an inch, a scale which is very frequently
adopted, and is sufficiently large to distinguish the buildings and
small plots, except in closely populated districts. This scale also
gives ample room for reference numbers.
The Parliamentary plans and sections must be accurate in delineation,
levels, and description. All property within the prescribed limits of
deviation must be clearly shown, and the numbers and description on
the plans and book of reference must be concise and complete, to
enable the owners to ascertain to what extent they will be affected.
In every place where it is proposed to interfere with any public
highway, street, footpath, river or canal, the manner of such proposed
alteration must be shown and described on both plan and section. The
commencement and termination of every tunnel must be correctly
indicated, and the length given on both plan and section. An omission
of any of the above requirements might prove very detrimental to the
scheme, and possibly result in the Bill being thrown out of Parliament
for non-compliance with standing orders.
[Illustration: Fig. 7.]
In carrying out the works the constructors have power to deviate the
centre line either to the one side or the other, provided that such
deviation will permit of the boundary of the works, or property to be
acquired, to come within the limits of deviation or property 18
referenced, and they may also vary the levels of the line to the
extent prescribed in the standing orders.
Figs. 5 and 6 are parts of a Parliamentary plan and section showing
alteration of a public road with an overline bridge--also a diversion
of a small river to avoid two river bridges.
Figs. 7 and 8 are parts of a Parliamentary plan and section showing a
public road diverted and carried under the railway.
A stipulated time is fixed in the Bill for the purchase of the
property and construction of the line, and if this time be exceeded
before the completion of the works, it will be necessary to obtain
further Parliamentary powers for an extension of time.
Every new railway, or extension of railway, in the United Kingdom,
must be inspected, and certified, by one of the inspecting officers of
the Board of Trade, previous to Government sanction being granted for
its opening as a passenger line.
To facilitate these inspections, and as a guide both to their own
inspecting officers and the engineers in charge of the construction,
the Board of Trade have issued a list of the principal requirements in
connection with all new lines.
The following is a copy of the list so far as relates to works of
construction and signals:--
Requirements of the Board of Trade.--1. The requisite apparatus
for providing by means of the block telegraph system an adequate
interval of space between following trains, and, in the case of
junctions, between converging or crossing trains. In the case of
single lines worked by one engine under steam (or two or more coupled
together) carrying a staff, no such apparatus will be required.
2. Home-signals and distant-signals for each direction to be fixed at
stations and junctions, with extra signals for such dock, or bay
lines, as are used either for the arrival, or for the departure of
trains, and starting-signals for each direction, at all passenger
stations which are also block posts. On passenger lines all cross-over
roads and all connections for goods, or mineral lines, and sidings to
be protected by home and distant signals, and as a rule at all
important running junctions a separate distant-signal to be provided
in connection with each home-signal.
[Illustration: Fig. 8.]
_Signals may be dispensed with on single lines under the following
conditions_:--
(_a_) _At all stations and siding connections upon a line worked by 20
one engine only (or two engines coupled together), carrying a staff,
and when all points are locked by such staff._
(_b_) _At any intermediate siding connection upon a line worked under
the train staff and ticket system, or under the electric staff or tablet
system, where the points are locked by the staff or tablet._
(_c_) _At intermediate stations, which are not staff or tablet
stations, upon a line worked under the electric staff or tablet
system: Sidings, if any, being locked as in (b)._
3. The signals at junctions to be on separate posts, or on brackets;
and the signals at stations, when there is more than one arm on one
side of a post, to be made to apply--the first, or upper arm, to the
line on the left, the second arm to the line next in order from the
left, and so on; but in cases where the main, or more important line,
is not the one on the left, separate signal-posts to be provided, or
the arms to be on brackets. Distant-signals to be distinguished by
notches cut out of the ends of the arms, and to be controlled by home
or starting signals for the same direction when on the same post. A
distant-signal arm must not be placed above a home or starting signal
arm on the same post for trains going in the same direction.
In the case of sidings, a low short arm and a small signal light,
distinguishable from the arms or lights for the passenger lines, may
be employed, but in such cases disc signals are, as a rule,
preferable.
Every signal arm to be so weighted as to fly to and remain at danger
on the breaking at any point of the connection between the arm and the
lever working it.
4. On new lines worked independently, the front signal lights to be
green for “all right,” and red for “danger;” the back lights (visible
only when the signals are at “danger”) to be white.
_This requirement not to be obligatory in the case of new lines run
over by trains of other companies using a different system of
lights._
5. Facing points to be avoided as far as possible, but when they
cannot be dispensed with they must be placed as near as practicable to
the levers by which they are worked or bolted. The limit of distance
from levers working points to be 180 yards in the case of facing
points, and 300 yards in the case of trailing points on the main line,
or safety points of sidings.
[Illustration: Fig. 9.]
In order to ensure that the points are in their proper position before 22
the signals are lowered, and to prevent the signalman from shifting
them while a train is passing over them, all facing points must be
fitted with facing-point locks and locking-bars, and with means for
detecting any failure in the connections between the signal-cabin and
points. The length of the locking-bars to exceed the greatest
wheel-base between any two pairs of wheels of the vehicles in use on
the line, and the stock rails to be tied to gauge with iron or steel
ties. All points, whether facing or trailing, to be worked or bolted
by rods, and not by wires, and to be fitted with double
connecting-rods.
6. The levers by which points and signals are worked to be interlocked
and, as a rule, brought close together, into the position most
convenient for the person working them, in a signal-cabin or on a
properly constructed stage. The signal-cabin to be commodious, and to
be supplied with a clock, and with a separate block instrument for
signalling trains on each line of rails. The point-levers and
signal-levers to be so placed in the cabin that the signalman when
working them shall have the best possible view of the railway, and the
cabin itself to be so situated as to enable the signalman to see the
arms and the lights of the signals and the working of the points. The
back lights of the signal lamps to be made as small as possible,
having regard to efficiency, and when the front lights are visible to
the signalman in his cabin no back lights to be provided. The fixed
lights in the signal-cabin to be screened off, so as not to be
mistakable for the signals exhibited to control the running of trains.
If, from any unavoidable cause, the arm and light of any signal cannot
be seen by the signalman they must, as a rule, be repeated in the
cabin.
7. The interlocking to be so arranged that the signalman shall be
unable to lower a signal for the approach of a train until after he
has set the points in the proper position for it to pass; that it
shall not be possible for him to exhibit at the same moment any two
signals that can lead to a collision between two trains; and that,
after having lowered the signals to allow a train to pass, he shall
not be able to move any points connected with, or leading to, the line
on which the train is moving. Points also, if possible, to be so
interlocked as to avoid the risk of a collision.
[Illustration: Fig. 10.]
Home or starting signals next in advance of trading-points when 24
lowered, to lock such points in either position, unless such locking
will unduly interfere with the traffic.
A distant signal must not be capable of being lowered unless the home
and starting signals in advance of it have been lowered.
8. Sidings to be so arranged that shunting operations upon them shall
cause the least possible obstruction to the passenger lines.
Safety-points to be provided upon goods and mineral lines and sidings,
at their junctions with passenger lines, with the points closed
against the passenger lines and interlocked with the signals.
9. When a junction is situated near to a passenger station, the
platforms to be so arranged as to prevent, as far as possible, any
necessity for standing trains on the junction.
10. The junctions of all single lines to be, as a rule, formed as
double-line junctions.
11. The lines of railway leading to the passenger platforms to be
arranged so that the engines shall always be in front of the passenger
trains as they arrive at and depart from a station; and so that, in
the case of double lines, or of passing places on single lines, each
line shall have its own platform. At terminal stations a double line
of railway must not end as a single line.
12. Platforms to be continuous, and not less than 6 feet wide for
stations of small traffic, nor less than 12 feet wide for important
stations. The descents at the ends of the platforms to be by ramps,
and not by steps. Pillars for the support of roofs and other fixed
works not to be less than 6 feet from the edges of the platforms. The
height of the platforms above rail level to be 3 feet, save under
exceptional circumstances, and in no case less than 2 feet 6 inches.
The edges of the platforms to overhang not less than 12 inches. As
little space as possible to be left between the edges of the platforms
and those of the footboards on the carriages. Shelter to be provided
on every platform, and conveniences where necessary. Names of stations
to be shown on boards and on the platform lamps.
13. When stations are placed on, or near a viaduct, or bridge under
the railway, a parapet or fence on each side to be provided of
sufficient height to prevent passengers, who may by mistake leave the
carriages when not at the platform, from falling from the viaduct or
bridge in the dark.
[Illustration: Fig. 11.]
14. Footbridges or subways to be provided for passengers to cross the 26
railway at all exchange and other important stations. Staircases or
ramps leading to or from platforms to be at no point narrower than at
the top, and the available width to be in no case contracted by any
erection or fixed obstruction whatever below the top.
At all stations where crowding may be expected, the staircases or
ramps to be of ample width, and barriers for regulating the entrance
of the crowd at the top to be erected. If in such cases there are
gates at the bottom, a speaking-tube or other means of communication
between the top and bottom to be provided; and in all cases gates at
the bottom of a staircase or ramp to open outwards. For closing the
openings at the top, sliding bars or gates are considered best.
The steps of staircases to be never less than 11 inches in the tread,
nor more than 7 inches in the rise, and midway landings to be provided
where the height exceeds 10 feet.
Efficient handrails to be provided on both staircases and ramps, and
in subways where ramps are used the inclination not to exceed 1 in 8.
15. A clock to be provided at every station, in some conspicuous
position visible from the platforms.
16. No station to be constructed, and no siding to join a passenger
line, on a steeper gradient than 1 in 260, except where it is
unavoidable. When the line is double, and the gradient at a station or
siding-junction is necessarily steeper than 1 in 260, and when danger
is to be apprehended from vehicles running back, a catch-siding with
points weighted for the siding, or a throw-off switch, to be provided
to intercept runaway vehicles at a distance outside the home-signal
for the ascending line, greater than the length of the longest train
running upon the line.
Under similar circumstances, when the line is single, provision for
averting danger from runaway vehicles to be made--
(1) At a station in one of the following manners:--
(_a_) A second line to be laid down, a second platform to be
constructed, and a catch-siding or throw-off switch to be
provided on the ascending line inside the loop-points.
(_b_) A loop-line to be constructed lower down the incline than
the station platform with a similarly placed catch-siding or
throw-off switch.
(2) At a siding-junction in one of the following manners, except where 27
it is possible to work the traffic with the engine at the lower end
of a goods or mineral train, in which case an undertaking (see No.
35) to do so, given by the company, will be accepted as sufficient:--
(_a_) A similar loop to be constructed as in the case of a
station.
(_b_) Means to be provided for placing the whole train on sidings
clear of the main line before any shunting operations are
commenced.
17. Engine-turntables of sufficient diameter to enable the longest
engines and tenders in use on the line to be turned without being
uncoupled to be erected at terminal stations and at junctions and
other places at which the engines require to be turned, except in
cases of short lines not exceeding 15 miles in length, where the
stations are not at a greater distance than 3 miles apart, and the
railway company gives an undertaking (see No. 35) to stop all trains
at all stations. Care to be taken to keep all turntables at safe
distances from the adjacent lines of rails, so that engines, waggons,
or carriages, when being turned, may not foul other lines or endanger
the traffic upon them.
18. Cast-iron must not be used for railway under-bridges, except in
the form of arched-ribbed girders, where the material is in
compression.
In a cast-iron arched bridge, or in the cast-iron girders of an
over-bridge, the breaking weight of the girders not to be less than
three times the permanent load due to the weight of the
superstructure, added to six times the greatest moving load that can
be brought upon it.
In a wrought-iron or steel bridge, the greatest load which can be
brought upon it, added to the weight of the superstructure, not to
produce a greater strain per square inch on any part of the material
than five tons where wrought-iron is used, or six tons and a half
where steel is used.
The engineer responsible for any steel structure to forward to the
Board of Trade a certificate to the effect that the steel employed is
either cast-steel, or steel made by some process of fusion,
subsequently rolled or hammered, and of a quality possessing
considerable toughness and ductility, together with a statement of all
the tests to which it has been subjected.
19. In cases where bridges or viaducts are constructed wholly or 28
partially of timber, a sufficient factor of safety, depending on the
nature and quality of the timber, to be provided for.
_N.B.--The heaviest engines, boiler trucks, or travelling cranes in use
on railways afford a measure of the greatest moving loads to which a
bridge can be subjected. The above rules apply equally to the main
transverse girders and rail-bearers._
20. It is desirable that viaducts should, as far as possible, be
wholly constructed of brick or stone, and in such cases they must have
parapet walls on each side, not under 4 feet 6 inches in height above
the rail level, and not less than 18 inches thick.
Where it is not practicable to construct the viaducts of brick or
stone, and iron or steel girders are made use of, it is considered
best that in important viaducts the permanent way should be laid
between the main girders. In all cases substantial parapets, with a
height of not less than 4 feet 6 inches above rail-level must be
provided by an addition to the girders, unless the girders themselves
are sufficiently high. On important viaducts where the superstructure
is of iron, steel, or timber, substantial outside wheel-guards to be
fixed above the level of, and as close to the outer rails as possible,
but not so as to be liable to be struck by any part of an engine or
train running on the rails.
In the construction of the abutments or piers which support the
girders of high bridges and viaducts, cast-iron columns of small size
must not be used.
In all large structures a wind-pressure of 56 lbs. per square foot to
be assumed for the purpose of calculation, which will be based on the
rules laid down in the report, dated 30th May, 1881, of the committee
appointed by the Board of Trade to consider the question of
wind-pressure on railway structures.
21. The upper surfaces of the wooden platforms of bridges and viaducts
to be protected from fire.
22. All castings for use in railway structures to be, where
practicable, cast in a similar position to that which they are
intended to occupy when fixed.
23. The joints of rails to be secured by means of fish-plates, or by
some other equally secure fastening. On main lines, and lines where
heavy traffic may be worked at high speed, the chairs not to weigh
less than 40 lbs.; but on branch lines, or lines on which the traffic 29
is light, chairs weighing not less than 30 lbs. may be used.
24. When chairs are used to support the rails they must be secured to
the sleepers, at least partially, by iron spikes or bolts. With
flat-bottomed rails, when there are no chairs, or with bridge rails,
the fastenings at the joints, and at some intermediate places, to
consist of fang or other through-bolts; and such rails, on curves with
radii of 15 chains or less, to be tied to gauge by iron or steel ties
at suitable intervals.
25. In any curve where the radius is 10 chains or less, a check-rail
to be provided.
26. Diamond-crossings, as a rule, not to be flatter than 1 in 8.
27. No standing work (other than a passenger platform) to be nearer to
the side of the widest carriage in use on the line than 2 feet 4
inches, at any point between the level of 2 feet 6 inches above the
rails, and the level of the upper parts of the highest carriage doors.
This applies to all arches, abutments, piers, supports, girders,
tunnels, bridges, roofs, walls, posts, tanks, signals, fences, and
other works, and to all projections at the side of a railway
constructed to any gauge.
28. The intervals between adjacent lines of rails, where there are two
lines only, or between lines of rails and sidings, not to be less than
6 feet. Where additional running lines of rails are alongside the main
lines, an interval of not less than 9 feet 6 inches to be provided, if
possible, between such additional lines and the main lines.
29. At all level crossings of public roads, the gates to be so
constructed that they may be closed either across the railway, or
across the road at each side of the crossing, and a lodge, or, in the
case of a station, a gatekeeper’s box, to be provided, unless the
gates are worked from a signal cabin. The gates must not be capable of
being opened at the same time for the road and the railway, and must
be so hung as not to admit of being opened outwards towards the road.
Stops to be provided to keep the gates in position across the road or
railway. Wooden gates are considered preferable to iron gates, and
single gates on each side to double gates. Red discs, or targets, must
be fixed on the gates, with lamps for night use, and semaphore signals
in one or both directions interlocked with the gates, may be required.
At all level crossings of public roads or footpaths, a footbridge or a
subway may be required.
At occupation and field crossings, the gates must be kept hung so as 30
to open outwards from the line.
30. Sidings connected with the main lines near a public road level
crossing to be so placed that shunting may be carried on with as
little interference as possible with the level crossing; and, as a
rule, the points of the sidings to be not less than 100 yards from the
crossing.
31. At public road level crossings in or near populous places, the
lower portions of the gates to be either close barred, or covered with
wire netting.
32. Mile posts, half-mile, and quarter-mile posts, and gradient-boards
to be provided along the line.
33. Tunnels and long viaducts to be in all cases constructed with
refuges for the safety of platelayers. On under-bridges without
parapets, handrails to be provided. Viaducts of steel, iron, or timber
to be provided with manholes or other facilities for inspection.
34. Continuous brakes (in accordance with the Regulation of Railways
Act of 1889), complying with the following requirements, to be
provided on all trains carrying passengers, viz.--
(1) The brake must be instantaneous in action, and capable of
being applied by the engine-driver and guards.
(2) The brake must be self-applying in the event of any failure
in the continuity of its action.
(3) The brake must be capable of being applied to every vehicle
of the train, whether carrying passengers or not.
(4) The brake must be in regular use in daily working.
(5) The materials of the brake must be of a durable character,
and easily maintained and kept in order.
35. Any undertaking furnished by a railway company to be under the
seal, and signed by the chairman and secretary of the company.
Recommendations as to the Working of Railways.--1. There should
be a brake vehicle, with a guard in it, at or near the tail of every
passenger train; this vehicle should be provided with a raised roof
and extended sides, glazed to the front and back, and it should be the
duty of the guard to keep a constant look-out from it along his train.
2. All passenger carriages should be provided with continuous
footboards, extending the whole length of each carriage and as far as 31
the outer ends of the buffer castings. As passenger carriages pass
from one company’s line to another’s, it is essential for the public
safety that, although the widths of the carriages on the different
lines may differ from each other, the widths across the carriages from
the outside of the continuous footboard on one side, to the outside of
the continuous footboard on the opposite side, should be identical for
the carriages of all railway companies, so that the lines of rails may
be laid at the proper distance from the edges of the passenger
platforms.
3. There should be efficient means of communication between the guard,
or guards, of every passenger train and the engine-driver, and between
the passengers and the servants of the company in charge of the train.
4. The tyres of all wheels should be so secured as to prevent them
from flying open when they are fractured.
5. The engines employed with passenger trains should be of a steady
description, with not less than six wheels, with the centre of gravity
in front of the driving-wheels, and with the motions balanced. They
should, as a rule, be run chimney in front.
6. Records should be carefully kept of the work performed by the
wearing parts of the rolling stock, to afford practical information in
regard to them, and to prevent them from being retained in use longer
than is desirable.
7. In addition to the block-telegraph instruments, it is desirable
that there should be speaking-instruments, or telephones, for
communication between signalmen, and books for recording the running
of the trains.
8. When drovers or other persons are permitted to travel with goods or
cattle trains, suitable vehicles should be provided for their
accommodation.
9. It is considered that, in fixed signals, the front lights should
show--
Green, for all right;
Red, for danger;
and that back lights, visible only when the signals are at danger,
should show white.
10. Refuge sidings should be provided at all main-line stations where
slow trains are liable to be shunted for fast trains to pass them. If
at such stations it is impossible to provide refuge sidings, and slow 32
trains have to be shunted from one main line to the other to allow of
fast trains passing them, some simple arrangements should be supplied
in the signal cabins to help to remind the signalman of the shunted
train.
11. Efficient means should be adopted to prevent the accidental
opening of the doors of passenger trains.
* * * * *
To carry out the undertaking, the engineer has to prepare working
plans and sections to a somewhat larger scale than that adopted for
the Government or Parliamentary plans, and on which must be marked the
exact positions of the commencement of the curves, straight lines, and
gradients. The sites of all the over and under bridges must be shown,
and their angles of crossing noted. All road, river, or stream
diversions must be indicated, so that the work in connection with them
may be laid out on the ground. All culverts and drains must be marked,
and their size, depth, and direction described. Public road
level-crossings, and farm or occupation-road crossings, must be shown
in their proper positions.
The face-lines of the ends of all tunnels should be marked on the
working plan and section, and the position of any shafts, which may be
intended either for use in carrying on the work or for future
ventilation.
A considerable amount of investigation and negotiation will have to be
entered into before the locating of the above works can be finally
decided. The desire to meet the wishes and convenience of all parties
interested must of necessity be controlled by the physical
circumstances of each case; very little alteration can be made in the
level of the rails, although some variation may be made in their
position.
When fixing the depths of culverts and drains, attention must be paid
to any probable improvement in the drainage of the district, which
might at some future time necessitate the deepening of such of the
main culverts where the inverts had been laid too high.
Unless all these details are determined, and shown on the
working-plans before the works are commenced, there is the risk that
embankments may have to be opened out to admit of bridges and
culverts, and cuttings changed to permit of road diversions.
The entire centre-line of railway must be carefully staked out by 33
driving strong wooden pegs into the ground at the end of every chain
length, and along the course of these pegs the longitudinal section
must be taken. Three pegs, one on each side of the centre peg, are
generally placed at the commencement and termination of the curves.
When the longitudinal section has been plotted to scale, and the
course of the gradients and level portions worked out and drawn on,
then the heights of the ground level and formation level can be marked
at each chain, and from them the depths of the cutting and the heights
of the embankments can be ascertained and marked at each chain. In
addition to the longitudinal section, it will be necessary to take a
large number of transverse or cross sections at those pegs, or
intermediate points, where the ground is at all side-lying or
irregular. These cross-sections are necessary to determine the
side-widths, or distances to outer edge of slopes in cuttings or
embankments, and also to calculate the actual quantity of earthwork to
be executed. For convenience in taking out the quantities, these
cross-sections are generally plotted to a natural scale, that is to
say, to the same scale horizontal as vertical, as shown in the example
of cross-sections, Figs. 15 to 24. It is also necessary to obtain
information, by boring or otherwise, as to the material of which the
cuttings are composed, whether clay, gravel, or rock.
In laying out lines through fairly level plains and populous
districts, the absence of great natural obstacles will allow the
engineer to carefully consider how far it may be prudent to diverge to
the right or to the left, to accommodate towns and places which would
be excluded by a more direct through route. There will be ample range
for selection, and it will be rather the question of policy than
compulsion which will guide him in the route to be taken.
[Illustration: Fig. 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]
When, however, the locating passes from the lower ground, away up
amongst the hills and mountain ranges, it becomes an intricate study
whether it will be possible to lay out any line at all which may
possess gradients and curves practicable for railway working. The
question of property, population, or convenience of access, is here no
longer the controlling influence, but in its stead there are the far
more formidable natural difficulties to be overcome in working out a
trackway to the inevitable summit level. The chief endeavour will be
to gain length, and so reduce as much as possible the steepness of the
gradients which at the best must necessarily be severe. In some of the 35
earlier mountain lines constructed abroad the system of _zigzags_ was
introduced, as shown in Fig. 25. These _zigzags_ were laid out on
ruling gradients, one above the other, on the sides of the mountain
slopes with pieces of level at the apices, A, B, and C, on which
the engine could be changed from one end of the train to the other.
Although feasible in principle, the system entailed considerable loss
of time in train-working, and was not unattended with risk.
The more modern and simple method of working out the same idea is to
connect the main zigzag lines by curves or _spirals_, thus rendering
the route continuous and unbroken. By this arrangement the heavy work
and delay in starting or stopping the train at the apices, A, B,
and C, as shown on Fig. 25, is avoided, and the train can proceed
continuously on its circuitous journey. Fig. 26 shows an instance of
the zigzags and spirals, as carried out on an important railway
abroad. To have made a direct line from D to E, the most difficult
part of the route, would have involved a gradient of 1 in 11; but by
constructing the spiral course, as shown, the length was more than
trebled, and the gradient reduced to 1 in 35.
Fig. 27 is another example of spiral zigzags in which advantage was
taken to cut a short tunnel through a high narrow neck of rock at
G, and then by skirting round the hill the line was taken over the
top of the tunnel and along the side of the mountain to the summit tunnel
at H. By this means the line from F to H was laid out to an
average gradient of 1 in 42.
Fig. 28 shows the Cumbres inclines on the Mexican Railway. The route
had to be located through one of the rugged passes of the great Chain
of the Andes, whose mountain-sides rise most abruptly from the lower
plains, to the great upper-land plateau, some eight thousand feet
above sea-level. The ground to be traversed was so steep and difficult
that, even with the best available detours and greatest length that
could be obtained, the result was an average continuous gradient of 1
in 25 for 12 miles.
[Illustration: Fig. 25, 26, 27, 28, 29]
Fig. 29 is a plan of part of the St. Gothard Railway, showing the
principal tunnel 9¼ miles long, and some of the adjoining spiral
tunnels. The long tunnel through the great Alpine barrier was the only
means of forming a railway connection between the two points at Airolo
and Goeschenen. Constructed in a straight line, with easy gradients, 37
falling towards the entrances, efficiency of drainage has been
secured, and excessive strain on motive-power avoided. The approaching
valleys on each side were in some places too irregular and broken to
admit of zigzag loops, and the spiral tunnels were adopted instead.
The enlarged plan of two of the spiral tunnels will explain the method
of working. An ascending train enters the first tunnel at A, and
after passing round almost an entire circle, on a rising gradient,
emerges at a much higher level at the point B. Proceeding onward,
the train enters the second tunnel at C, and after passing round a
similar circle, on a rising gradient, comes out at a still higher
point, D, and continues its course up the valley.
The last five sketches illustrate some of the methods which have been
adopted when constructing railways through some of the most difficult
mountain ranges. They show what has been done, and may serve as guides
in working out the location of a line in some hitherto unexplored
region.
Gauge.--The gauge of a railway, or its width from inside to inside
of rails, affects both its cost and efficiency. If the gauge be
exceptionally wide, then the expenditure on works and rolling-stock
will be proportionately heavy; and although theoretically the extra
wide gauge may possess greater capabilities for accommodation and
high-speed travelling, we may find in practice that the necessary
requirements may be provided on a much more moderate gauge. On the
other hand, if the gauge be exceptionally narrow, there will be
diminished convenience both for passengers and merchandise, and a
corresponding limit to the speed in transit.
In isolated districts, where passenger traffic is of secondary
importance, and where the principal merchandise will be heavy without
being bulky, such as mineral ores, slates, etc., a comparative narrow
gauge may possibly suit the purpose. For main trunk lines, however,
where a large, heavy, and fast passenger traffic will have to be
worked, and where goods of all kinds, many of them bulky without being
heavy, will have to be carried, an ample gauge must be selected to
ensure convenience and safety. A liberal gauge permits the use of
commodious rolling-stock without any great amount of lateral
overhanging weight outside the wheels; whereas with a narrow gauge
there is the tendency--if not the necessity--to use vehicles which have
too great a lateral overhang for proper stability, except at very 38
moderate speeds.
The following list shows the gauges adopted in various countries:--
ft. ins.
England, Scotland,
and Wales 4 8½
Ireland 5 3
United States 4 8½, with some lines 5 ft., 5 ft. 6 ins., and 6 ft.
Canada 4 8½ and 5 ft. 6 ins.
France 4 8½
Belgium 4 8½
Holland 4 8½
Germany 4 8½
Austria 4 8½
Switzerland 4 8½
Italy 4 8½
Turkey 4 8½
Hungary 4 8½
Denmark 4 8½
Norway 4 8½ and 3 ft. 6 ins.
Sweden 4 8½
Mexico 4 8½ and 3 ft.
Egypt 4 8½ and 3 ft. 6 ins.
Peru 4 8½
Nova Scotia 4 8½ and 5 ft. 6 ins.
New South Wales 4 8½
Brazil 4 8½, 5 ft. 3 ins., and 5 ft. 6 ins.
Uruguay Republic 4 8½
Russia 5 0
South Australia 5 3
New Zealand 3 6
British India 5 6 and 1 metre.
Ceylon 5 6
Spain 5 6
Portugal 5 6
Chili 5 6
Argentine Republic 5 6
Cape Colonies 3 6
Japan 3 6
After many years’ experience of actual working, the broad, 7 feet,
gauge of the Great Western Railway has been abandoned for the 4 feet
8½ inch gauge. Doubtless this decision was the result of most careful
deliberation, and was made upon convincing proof that the 4 feet 8½
inch gauge could fulfil all the advantages claimed for the wider
gauge, whilst at the same time it possessed the merit of less cost of
construction and working, and greater facilities for the exchange of
traffic with other lines having the standard gauge. The facility of
exchange, or through working of rolling-stock, is a leading element of
successful railway working, and it is difficult to estimate what would
be the amount of loss and delay if we had any great extent of break of
gauge on the main trunk lines of our own country.
Although some countries have selected gauges of 5 feet and 5 feet 39
6 inches, it is interesting to note that the largest number have
adopted the English standard gauge of 4 feet 8½ inches, and that the
miles of line laid to this gauge far outnumber all the others. The
fact that our own home lines, the principal Continental lines, and
nearly all that vast network of railways in the United States of
America, have been laid to the 4 feet 8½ inch gauge, testifies to the
general opinion of its utility and efficiency; and we know that
included in that list are the railways which carry the largest,
heaviest, and fastest train service in the world.
It would be interesting to trace back, and, if possible, ascertain
from whence the exact gauge of 4 feet 8½ inches was derived. No doubt,
in the early days of the pioneer iron highways in England, the
railways were made the same gauge as the tramroads which they
superseded. But why was 4 feet 8½ inches the gauge of the tramroads?
We may reasonably infer that the first four-wheeled waggons used on
the early tramroads were in reality the same waggons which had been
previously used on the common roads for the conveyance of coal and
minerals to the ports for shipment, and that the waggons were merely
transferred from the roughly paved or macadamised roads to the
tramroads. Flanged wheels were then unknown, and the introduction of
the tram-plates was at first simply designed to lessen the resistance
to haulage. The gauge, or width between the wheels, of these waggons
may have been the outcome of long experience as to the most suitable
width for convenience of load, stability during transit, or for space
occupied on the highway. The width may have been handed down from
generation to generation, going back to the time when wheeled vehicles
were first built in the country. Perhaps in the beginning the first
vehicles may have been imported from Italy, or Greece--countries which
in the earlier ages were the most advanced in matters of luxury and
convenience.
When in Pompeii, a few years ago, the writer measured the spaces
between a large number of the _wheel-ruts_ which are worn deep
into the paving-stones in many of the principal streets of that
wonderful unearthed city. These paving-stones, very irregular in
shape, and many of them 2 feet 6 inches long by 1 foot 6 inches wide,
are carefully fitted together, and form a compact massive pavement
from curbstone to curbstone. The wheel-tracks, which are in many
places worn into the stones to the depth of an inch or an inch and a 40
half, are always distinct, and there is no difficulty in defining the
corresponding track.
The result of a large number of measurements gave an average width of
about 4 feet 11 inches from centre to centre of the wheel-tracks, a
curious coincidence with the gauge of our own road vehicles at the
beginning of the railway era. Whether our selection of the railway
gauge of 4 feet 8½ inches has been the result of study, imitation, or
caprice, we certainly have the silent testimony of these old deep-worn
stones to prove that two thousand years ago the chariots of Pompeii
were of very similar gauge to our own of modern times.
Narrow-gauge railways, of gauges varying from 1 foot 10½ inches on the
Festiniog Railway, to 3 feet, 3 feet 3 inches (metre), and 3 feet 6
inches, have been made in several places both at home and abroad.
Generally speaking, they have been constructed as subsidiary or
auxiliary lines in thinly populated districts, with a view to afford
some railway accommodation where it was considered that lines of the
standard gauge would not pay. In some instances abroad long lines of
narrow gauge--3 feet and 3 feet 6 inches--have been constructed as
main trunk lines in newly opened out districts. Some of these have
since been altered to a wider gauge as the traffic developed, and
experience proved that the narrow width of the vehicles was unsuitable
for quick transit, or convenience in the accommodation of passengers
and goods.
The object in making a line to a narrow gauge is doubtless to save
cost in the original construction; but when a scheme for an altered
gauge is put forward, it will be well to consider what amount of
advantage or saving would be effected by deviating from the standard
gauge.
If there be almost a certainty that such proposed line will always
remain isolated from all other existing railways of the standard
gauge, then perhaps the selection of gauge may be one of minor
importance, and there remains but the question whether the description
of traffic, and the weights to be carried, can be worked to any
greater advantage, or more economically, by deviating from the
standard gauge.
If, however, there be a fair probability that such proposed line may
at some future time become part of an already established railway
system, it would appear to be more prudent to make the line to the
standard gauge, and effect economies by introducing steeper gradients, 41
sharper curves, and lighter permanent way, and keep down working
expenses by using lighter locomotives, worked at slower speeds.
High speeds are not expected on narrow gauge railways, and no
complaints are made about passenger trains whose highest running speed
does not exceed 20 miles per hour. By conceding the same indulgence to
light railways made to the standard gauge, great economies might be
introduced both in their construction and working. The similarity of
gauge would admit the transit of the carriages and waggons of other
standard gauge lines, and so avoid all cost and delay in transshipment.
The heavy engines could be kept for the main-line working, and light
engines for slow speeds would serve for the light standard-gauge
lines. As traffic developed, and the train service required heavier
and faster trains, the light rails could be removed, and replaced by
those of heavier section to correspond to the main line. The
similarity of gauge would permit uninterrupted transit of all vehicles
to a common centre for repairs, whereas the narrow gauge carriages and
waggons, being limited to running only on their own district, must
have separate workshops for their repair.
When considering the cost of construction and working of a
narrow-gauge railway as compared with one of the standard gauge, there
are certain items which are common to both, and in which the narrow
gauge could not be expected to obtain any advantage over the standard
gauge.
There would not be any saving in getting up the scheme in the first
instance;
Nor in the Parliamentary expenses;
Nor in the engineering or carrying out of the works;
Nor in the station accommodation, waiting-rooms, and offices;
Nor in the signals and interlocking arrangements;
Nor in the telegraph;
Nor in the working staff and train men;
Nor in the maintenance of the permanent way, as the same number of men
would be required for the inspection and packing of the road, perhaps
more.
Little or no saving could be expected in the bridges under the
railway, as these must be made to the prescribed widths and heights,
irrespective of the gauge of the railways.
Little, if any, saving could be made in river or stream bridges, as the 42
same amount of waterway would have to be provided in each case.
The same remark applies to culverts and drains.
There would, on the other hand, be a small saving in the quantity of
land to be acquired to the extent of a narrow strip or zone,
represented by the difference in width between the narrow and standard
gauges.
There would also be the same small proportionate saving in the
embankments and cuttings to the extent of the difference in gauge.
Also a saving in the overline bridges and road approaches in
consequence of less width and height of the opening through those
bridges.
And a saving in the rails, sleepers, and ballast of the permanent way,
to the extent consistent with efficiency. That some saving may be
effected in these is undoubted, but it is necessary to exercise
caution, and not rush to the opposite extreme by making the parts too
light. A rail should be made not only strong enough to carry well the
engines that have to pass over it, but it should also be heavy enough
to stand the wear of several years. Narrow-gauge engines must be heavy
in conformity with the loads they have to haul. The same amount of
power must be exerted to haul a hundred tons on a given gradient,
whether the gauge be narrow or broad. In some cases of narrow-gauge
railways the original rails, which weighed only 45 lbs. per yard, have
since been replaced with others weighing 60 and 65 lbs. per yard. The
light 45 lb. rails were evidently not found to be sufficiently heavy
to keep the road to proper line and level. The result of our everyday
practice seems to prove that there is not only an advantage, but an
economy, in adopting rails of a heavy section, and experience would
therefore indicate that even for a narrow-gauge railway it may not be
expedient to adopt rails weighing less than 65 lbs. per yard.
Gradients.--There are very few localities where the rails on any
line of railway can be laid perfectly level or horizontal for more
than comparatively short distances. By far the greater portion have to
be laid on inclined planes of varying rates of inclination to suit the
general formation of the district traversed, and the circumstances of
the line to be constructed.
The degree, or rate of inclination, of these inclined planes, or
gradients, may be expressed in various ways. A very general method is 43
to state the number of feet, metres, etc., which can be measured along
the gradient before an increased rise or fall of one foot or metre,
etc., is obtained. Thus a gradient of 1 in 200 signifies a rise or
fall of 1 foot in 200 feet, or 1 metre in 200 metres.
Sometimes the rate of inclination is expressed by stating the number
of feet of rise or fall in a mile. In this way a gradient would be
described as falling at the rate of 30 feet in a mile, rising at the
rate of 20 feet in a mile, etc. Twenty feet to a mile is equal to 1 in
264.
Another method is to give the percentage of rise or fall. In this way
the inclination would be expressed as a 1 per cent. gradient, 2 per
cent. gradient, ½ per cent. gradient, etc., which for comparison would
signify 1 in 100, 1 in 50, and 1 in 200 respectively.
The gradients of a railway most materially influence its facility and
cost of working, and every effort should be used to make them as easy
as possible consistent with the prospect of the line.
Steep gradients signify heavy locomotives, increased cost of
motive-power, reduced speed, and light loads.
The following tabulated memoranda show the approximate loads,
exclusive of engine and tender, which can be hauled on the level and
on certain inclines at various speeds by engines of the quoted
capacities and steam admissions. A medium-sized, ordinary type of
passenger and goods engine has been selected for each of the examples.
The working of the passenger engine and train is assumed to be under
favourable circumstances, with fine weather, fairly straight line,
first-class permanent way, modern rolling-stock with oil axle-boxes
and perfect lubrication, and all the conditions most suitable to
ensure the least resistance to the moving load. For the goods engine
and train a greater resistance per ton of load is assumed, as the
goods trucks are never so perfect or easy in the running as the
passenger carriages. A certain amount of side wind is taken into
consideration, and also an allowance for moderately sharp curves, the
object being to indicate what may be looked upon as fair, average,
workable loads.
The loads for engines of larger or smaller dimensions, or higher or
lower pressures, may be obtained by working out the proportion between 44
the tractive force put down in any of the columns of the tabulated
memoranda and the ascertained tractive force of any other engine under
the same conditions of cut-off and speed.
-----------------------+-------------------------+-------------------------
| PASSENGER ENGINE. | GOODS ENGINE.
| |
|Six wheels, driving |Six wheels, all coupled,
| and trailing wheels | 4 ft. 6 ins. diameter.
| coupled, 6 ft. 6 ins. | Cylinders,
| diameter. Cylinders, | 17 ft. × 24 ft.
| 17 ft. × 24 ft. | Locked-down pressure on
| Locked-down pressure on | safety-valves, 140 lbs.
| safety-valves, 140 lbs. | per square inch. Assumed
| per square inch. Assumed| pressure at cylinders,
| pressure at cylinders, | 120 lbs. per square inch.
| 120 lbs. per square |
| inch. |
| |
|Weight of engine 39 tons.|Weight of engine 34 tons.
| ” tender 24 ” | ” tender 24 ”
| -- | --
| 63 ” | 58 ”
-----------------------+-----+-----+------+------+-----+-----+------+------
Assumed cut-off | ¼ | ⅓ | ½ | ¾ | ¼ | ⅓ | ½ | ¾
” mean effective | | | | | | | |
pressure, lbs.| 45 | 56 | 76 | 100 | 45 | 56 | 76 | 100
” tractive force,| | | | | | | |
lbs. | 4000| 4979| 6758 | 8892 | 5780| 7192| 9760 | 12844
Speed in miles per hour| 60 | 40 | 30 | 15 | 40 | 30 | 20 | 15
| | | | | | | |
|Tons.|Tons.|Tons. |Tons. |Tons.|Tons.|Tons. |Tons.
| | | | | | | |
Level | 97 | 230 | 447 | 892 | 213 | 358 | 623 | 907
1 in 1000 | 84 | 196 | 373 | 707 | 187 | 310 | 532 | 768
” 800 | 81 | 188 | 358 | 671 | 181 | 299 | 512 | 739
” 600 | 76 | 177 | 335 | 618 | 172 | 285 | 482 | 695
” 400 | 68 | 157 | 296 | 533 | 157 | 257 | 432 | 621
” 300 | 60 | 141 | 263 | 467 | 143 | 233 | 390 | 560
” 250 | 55 | 129 | 241 | 424 | 133 | 216 | 361 | 519
” 200 | 47 | 114 | 213 | 372 | 120 | 195 | 324 | 467
” 150 | 37 | 93 | 177 | 304 | 101 | 165 | 276 | 397
” 100 | 21 | 63 | 126 | 217 | 74 | 123 | 208 | 302
” 90 | -- | 56 | 114 | 197 | -- | 113 | 191 | 279
” 80 | -- | 48 | 101 | 175 | -- | 101 | 172 | 253
” 75 | -- | 43 | 94 | 164 | -- | 95 | 163 | 240
” 70 | -- | 39 | 86 | 152 | -- | 88 | 153 | 226
” 60 | -- | 28 | 70 | 128 | -- | 74 | 131 | 196
” 50 | -- | -- | 53 | 101 | -- | -- | 107 | 163
” 40 | -- | -- | -- | 73 | -- | -- | -- | 127
” 25 | -- | -- | -- | 27 | -- | -- | -- | 67
-----------------------+-----+-----+------+------+-----+-----+------+------
NOTE.--The column loads in tons are exclusive of the weight of
engine and tender.
From the above memoranda it will be seen how greatly the gradients 45
affect the loads. For an important main trunk line, with a heavy and
frequent train-service of passengers and goods, the introduction of
steep gradients would not only reduce the speed of the train-working,
but would probably involve the necessity of assistant engines over
those parts of the line; and it may be prudent, where possible, to
incur heavier earthworks, or considerable detours, or tunnels, to
obtain more favourable gradients. For such a line the additional cost,
and the extra distance caused by a detour of a mile or more, will be
of far less importance than the interruption in the train service
arising from a serious reduction in speed or taking on assistant
engines. On many railways abroad there are very interesting examples
of long detours of several miles, carefully studied out to obtain
greater length and easier gradients, resulting in the construction of
lines over which the traffic can be worked without necessitating
auxiliary engine-power. On the other hand, there are situations where
steep gradients cannot be avoided, where certain altitudes must be
reached, and where there is no alternative but to face the inevitable.
On secondary lines, and short branch lines, where the traffic is not
expected to be heavy, and where speed is not so important, it may be
policy to economize outlay and introduce steeper
gradients than on the main line.
Half a mile of a rather steep gradient is not felt so much when it is
situate midway between two stations, because the attained speed of the
train assists the engine over the short distance to the summit; but
when it occurs as a rising gradient out of a station, it forms a great
check to the working, particularly in bad or wet weather, when there
is the risk of the engine slipping, and the entire train sliding back
into the station.
Long steep gradients not only necessitate increased motive-power for
the ascending trains, but also require increased brake-power, and
precautionary measures for the descending trains. Where passenger
trains are fitted with continuous brakes, the risk of losing control
is minimized; but with goods trains composed of waggons, having only
the ordinary independent side-lever brake, it will be found absolutely
necessary in many cases to have additional heavy brake-vans for
descending the inclines, and these special vans, unfortunately, will
form so much extra non-paying weight to be hauled up on the ascending
trains. Of course, it is quite possible--and, indeed, in many places 46
it is customary--to pin down some of the side-lever brakes before
commencing the descent, but once pinned down the brakes cannot be
eased or taken off until the entire train is brought to a stand.
Every goods waggon should be fitted with a brake, and it would be of
immense value if that brake could in all cases be applied and
controlled when the train is in motion.
The American type of long goods waggon, with a four-wheel bogie-truck
at each end, is fitted with a brake very similar to those adopted on
the ordinary horse tram-cars. On the top of the waggon a horizontal
iron hand-wheel, about 18 inches in diameter, is fixed on to a strong
vertical iron rod, which works in brackets, and extends down below the
underside of waggon framing. One end of a short length of chain is
secured to the foot of the vertical rod, and the other end is
connected by light iron rods to the series of levers which pull on the
brake-blocks. By rotating the horizontal hand-wheel the chain is
coiled round the lower end of the vertical rod, the brake-levers are
pulled over, and brake-pressure applied to the wheels of the waggon.
The brakesman is supplied with a convenient seat and footboard, and on
the floor-level of the latter there is a pawl and ratchet attached to
the vertical rod, which permits the brakes to be applied to the extent
required. The pawl retains the brakes in position until the brakesman
with his foot pushes the pawl out of the notch of the rachet and
releases the brake gearing, which is at once pulled off quite clear by
strong bow-strings attached to the framework of the bogies.
This type of hand-brake is, perhaps, the simplest that can be made.
The brakesman has merely to put it on, the pawl and ratchet keep it
on, and the bow springs take it off when no longer required. Each one
of these long, loaded goods waggons becomes a very serviceable
brake-van, and for ascending and descending steep inclines all that is
necessary is to take on a few additional brakesmen to manage the
brakes of as many suitable waggons. These incline brakesmen, after
going down, can return to the summit by the next ascending train,
their small weight being a mere nothing as compared with that of
special or extra brake-vans.
On some European lines it is the custom to sprag some of the goods
waggon wheels when going down exceptionally steep inclines, as well as 47
applying the brakes on the ordinary and extra brake-vans. The sprag is
a piece of wood, circular in section, about 2 feet 6 inches long, and
5 to 6 inches thick in the middle, tapering off to about 2 inches
thick at the ends. When the waggon-wheel is just beginning to move,
the sprag is inserted between the spokes, and being caught against the
waggon framework, the wheel is held fast, and being unable to revolve,
remains fixed, and acts like a skid upon the rails. The skidding of
the wheels upon the rails wears flat places on the wheel tyres, and it
is needless to mention that the practice is only resorted to in very
extreme cases. Although a very primitive means for checking the speed
of a descending train, or for maintaining vehicles stationary on an
incline, there have been many instances where lives have been saved
and accidents prevented by the prompt use of a few sprags. Solid or
close wheels cannot be spragged, only wheels which have spokes or
openings, and for this reason alone it would be very desirable that in
every passenger and goods train there should be some spoke or open
wheels which could be spragged as a last resource, in the event of a
sudden emergency of brakes failing or train becoming divided on an
incline.
On ascending gradients there is always the risk of a coupling
breaking, and the train becoming divided. If the detached portion left
behind be provided with ample brake-power, hand-brakes, or otherwise,
no harm may take place beyond a little delay; but if the brake-power
be insufficient or defective, and if all the wheels are solid wheels
incapable of admitting a few timely sprags, then the vehicles cannot
be held, but must slide back, and running unchecked would soon attain
such a velocity as would cause them either to leave the rails or dash
into another train standing at the last station. Many lamentable
accidents have taken place arising from portions of trains breaking
away and running back, and the sad experience of those casualties
should call forth every effort to avert a recurrence in the future. It
may not always be possible to detect a hidden flaw in a coupling, or a
defect in the brake-gearing until the actual failure occurs; but it is
quite possible to guard against disastrous results from such failure,
by providing means to hold the vehicles, and prevent them sliding
back.
For some years the writer had the entire charge of an important
railway abroad on which the gradients were very exceptional, and where 48
it was absolutely necessary that he should organize the most complete
precautions to prevent the possibility of trains, or portions of
trains, running back down inclines. Starting from sea-level, the line,
which was laid to the 4 feet 8½ inch gauge, rose to a summit of over
8000 feet, and on the mountain division there were many long gradients
of 1 in 40, 1 in 33, and in one place a continuous gradient of 1 in 25
for 12 miles. The specially powerful engines reserved for these heavy
inclines were each supplied with an ordinary hand-brake, a
steam-brake, and a Westinghouse continuous brake. The passenger
carriages, which were of considerable length, and carried on a
four-wheeled bogie-truck at each end, were all fitted up with the
Westinghouse brake, and in addition each carriage had its own
hand-wheel brake with the pawl and ratchet gearing. All the goods
waggons, which were of the American type, were fitted with hand-wheel
brakes similar to those on the carriages. Special gangs of trained
brakesmen took charge of the trains on these inclines, a brakesman to
every carriage or waggon, and were always in readiness in case of the
breakage of a coupling, or the failure in the Westinghouse brake or
brakes on engine. The immunity from accidents justified the combined
precautions adopted, and proved the possibility of working such severe
gradients with perfect safety.
The long-continued application of the brakes on heavy inclines
naturally leads to the question as to the description of wheel to be
adopted for the work. Not only are the wheels subjected to very severe
torsional strains, but the temperature at the circumference is raised
very high in consequence of the friction. Perhaps, theoretically, the
safest wheel would be one made out of a solid piece of metal, similar
to the chilled cast-iron wheels of the United States, or the steel
disc wheels used on some lines in Europe, in either of which holes can
be left for sprags. Wheels of this description can withstand very
heavy wear and tear, they are not affected by increased temperature,
and they certainly have the minimum of parts to work loose. Of the
built-up wheels, the strong forged-iron-spoke wheel with steel tyres
shows excellent results, and always gives due warning of loosening by
indications at the tyre rivets. The suddenness with which the solid
wooden centre wheels sometimes break up and fall to pieces does not
commend them for a service where there must be a long-sustained
application of the brakes. The increased temperature which expands the 49
tyre, contracts the wood, and must loosen and weaken the entire wheel.
On all steep gradients the road-bed should be of the most substantial
character, and the permanent way of a strong description, and
maintained in perfect order, as the engines for working the traffic
must necessarily be of a heavy type. The rails will be severely tested
by the pounding and slipping of the engines on the ascending journey,
and by the action of the brakes on the descending journey.
In the early days of the railway system, rope-haulage was adopted on
some of the main lines for working the trains on steep inclines near
the principal terminal stations. A powerful stationary engine, located
at the highest point, was employed to work an endless rope which
passed round large drums at the top and bottom of the incline, and was
supported on sheaves or pulleys fixed between the rails. The
connection between the carriages and endless rope was effected by
means of a short piece of rope called the _messenger_, which was
coiled round the main rope in such a manner as to be readily detached
when the train reached the summit. There are many persons who will
remember the time when the passenger trains were hauled by an endless
rope up the 1 in 66 incline from Euston to Camden Town, a distance of
about a mile and a half, and up the 1 in 48 incline from Lime Street,
Liverpool, to Edge Hill, a distance of about a mile and a quarter, and
several others. The rapid strides made in locomotive construction, and
the increased pressure used in the boilers, enabled much more powerful
engines to be built, until one by one the rope-haulage machinery has
disappeared from nearly all the inclines where for years it had been
considered indispensable. Rope-haulage on inclines is now very rarely
met with, except at collieries and ironworks, where occasionally the
rope may be seen so arranged that the loaded waggons descending pull
up the empty waggons on the opposite or parallel line.
Curves.--The degree of curvature of a railway curve is generally
expressed by giving the radius in feet, chains, metres, or other
national standard measure.
When laying out a line of railway, the natural features of the country
will necessitate the introduction of curves, and the question for
consideration will be whether they are to be made of small or large
radius. In some cases sharp curves are inevitable, except by incurring 50
enormous works which would not appear to offer any corresponding
prospective recompense. In others the curves may be made of easy
radius, at a comparative moderate extra outlay, if the character of
the line and description of traffic to be accommodated will warrant
the expenditure. For main through lines, with heavy, high-speed
traffic, it is advisable to have the curves of large radius, so as to
avoid the necessity of reducing speed when passing round them.
Although a high-class fast train may be allowed to run round an 80
chain (5280 feet) curve at almost unrestricted speed, safety demands
that there should be a reduction of speed on curves of 40 or 30 chains
radius, and a very much greater reduction for curves of 20 chains
radius and under. A sharp curve will in some places form a greater
check to fast trains than a length of moderately steep gradient on a
straight line. In the former the trains running in either direction
must slow down for some distance before reaching the curve, round
which they should pass at greatly reduced speed, and then some
distance must be run before they can attain their full speed again. On
the other hand, with a rising gradient, on a fairly straight line, the
acquired momentum of the train will materially assist in ascending the
incline, and although the speed may be slackened as the train
advances, there may not be any very great diminution in the running
before the gradient is passed, and average level line reached again. A
reduced rate of running must be maintained round curves of small
radius, for, however substantial the works and permanent way, and
however well devised and constructed the rolling-stock, there is an
element of danger ever present when passing round sharp curves at
anything more than moderate speed. In the great rush for fast through
trains this point is very apt to be overlooked, and too little time
allowed for the running. Even with the fastest trains on any line
there are some portions of the route which must be traversed with
greater caution and less speed than others, either on account of sharp
curves or of gradients; and if those who are entrusted with the
preparations of the time tables do not possess the technical
information necessary to deal properly with the question of relative
speeds, there is the strong probability that the programme prepared
may be one both difficult and dangerous to fulfil. The spirit of
rivalry is a strong incentive to fast running, but prudence and common
sense should indicate that record speeds should only be attempted on 51
the straight or favourable portions of the line. There is,
unfortunately, the growing tendency to run faster and faster round the
curved portion of our lines, heedless of the close approach to the
limit of safety, and unless this excessive speed be controlled in
time, the result must be disaster on a very large scale.
A sharp curve leading into or out of a terminal station or main-line
stopping-station does not so much affect the train running as a sharp
curve at an intermediate point between stations where the train may be
expected to run at its maximum speed. Wherever it is possible it is
very desirable to avoid sharp curves on inclines, because there are
times when descending trains may acquire a considerable velocity, and
wheels tightly gripped by the brakes have not the same facility for
following the curves as when they are running free.
In rugged and mountainous districts sharp curves are almost
unavoidable, except by introducing a series of tunnels; but in these
districts both the gradients and curves are alike exceptional, the
speed is necessarily slow, and special precautions are taken for the
ascending and descending trains.
[Illustration: Fig. 30, 31, 32, 33, 34, 35, 36, 37, 38]
When setting out reverse curves on a main line a piece of straight
line should always be laid in between the termination of the one curve
and the beginning of the other, to allow of a proper adjustment of the
rails to suit the super-elevation adopted on each of the adjoining
curves. In station yards and sidings this is not so absolutely
necessary, the sorting of the carriages and waggons and the
marshalling of the trains being carried on at a low speed, which does
not necessitate any super-elevation of the rails on the curves. The
speed of the train regulates the amount of super-elevation to be given
on any particular curve, and to ensure smooth and safe running this
amount must be maintained uniform all round the curve. On curves of
small radius, guard, or check, rails are frequently placed alongside
the inner rail, as in Figs. 30 to 33, to check the tendency of the
engine to leave the rails and run in a straight line. For the
bull-head road a special chair is used, which holds both the
running-rail and the check-rail, as shown on the sketch, the rails
being kept the proper distance apart by the web portion in the centre,
which forms part of the casting. For the flange railroad, check-rails
are sometimes made of strong angle irons placed against the flange of
the running-rail, and bolted to the transverse sleepers. This method 53
is not nearly so strong or efficient as the arrangement shown on Fig.
33, with a cast-iron distance-block about six inches long, placed
between the running-rail and check-rail, and all tied together with a
strong through bolt. A bolt-hole is punched in the edge of the flange
of check-rail, and a crab bolt and clip holds the two rails on the
sleeper. The cast-iron distance-blocks are placed just outside the
sleeper, so as not to interfere with the holding-down bolt. Doubtless
these guard rails do good service, but if the leading wheels of the
engine have sharp or worn flanges there is the possibility that the
wheel, pressing against the high rail, may mount the rail, and throw
the train off the line. A more secure method is to place the guard
outside the high rail, as in Figs. 34 to 38. This can be done by securing
a strong continuous longitudinal timber to the cross-sleepers--or to
the cross-girders in the case of a girder bridge--with its outer or
striking edge protected with a fairly heavy angle iron. The top of
this outside guard above the rail level may be three inches or more,
according to the height of any hanging spring, or portion of brake
apparatus belonging to the rolling-stock. The distance between the
striking-face of the guard and the inside of head of rail should be
about 5 inches, or such width that before the flange of the wheel can
mount on the top of the rail, the face of the wheel-tyre will be
brought into contact with the striking-face of the outside guard, and
thus effectually prevent the wheel leaving the rail. The sketches show
some of the types applicable to the chair road, and to the flange
railroad. In Figs. 34, 35, and 37, the outside brackets are of heavy
angle iron cut off in lengths to correspond to the width of the
sleeper. In Fig. 36 the cast-iron chair is lengthened, and has an end
bracket to support the guard timber. In Fig. 37 a hard wood bolster is
fastened on the top of each sleeper, and on this is placed the
continuous guard timber. This method of increased security is
frequently adopted on girder bridges and long iron viaducts which are
on the straight, and in such cases it is usual to place the guards
outside each of the rails forming the track.
The introduction of bogie engines and bogie carriages has conduced
largely to the safe working of the train-service over the curved
portions of many of our home railways, as well as to the economy in
the wear and tear of permanent way and rolling-stock. The action of
long rigid wheel-base vehicles passing round sharp curves is 54
detrimental to all the parts brought into contact. Not only is there
the constant tendency to mount the rails, and spread the gauge, but
the tiny shreds of steel scattered all along close to the
rail--particles ground off the rails, or off the wheel-tyres, or
both--testify to useless wear, unnecessary friction, and great waste
of motive-power.
The gradual increase of accommodation and conveniences in the carriage
stock of European railways led to the gradual increase in the length
of the vehicles. The six-wheeled carriage superseded the four-wheeled
carriage, on account of its increased steadiness when running, but the
introduction of long sleeping-cars, dining-cars, and corridor cars
necessitated some better wheel arrangement than the ordinary six-wheel
type could supply. The six wheels had been spread as far apart as was
admissible for carrying weight and passing round curves, and something
had to be done to meet the demand for still longer carriages. Many of
the six-wheeled carriages at present running on our own home lines
have a fixed wheel-base as long as 22 feet, and with this length the
horn-plates must undergo a very considerable strain when adapting
themselves for the passage round curves of small radius. On a curve of
15 chains radius (990 feet) a chord of 22 feet will have a versed sine
or offset of 0·73 of an inch, and on a curve of 10 chains radius (660
feet) an offset of 1·10 of an inch. Fortunately, curves of the above
small radius are not very numerous on our main lines; but wherever
they do occur, the conflict between the long fixed wheel-base
rolling-stock and the permanent way must be very severe to both.
Several descriptions of eight-wheeled carriages have been tried on our
home lines; but the system which is now most in favour is the ordinary
bogie truck, which has been in use for so many years on all American
railways. A bogie truck is really a short carriage frame complete in
itself, with its wheels, springs, and brake appliances, and is
attached to the under side of the carriage body by a central pivot,
round which the truck can swivel or rotate sufficiently to adapt
itself to the curved portions of the line. With a bogie truck at each
end of a long carriage, the vehicle will pass as easily round curves
as on the straight line, side pressure, or grinding against the rails,
is obviated, and friction is reduced to a minimum. The bogie truck may
consist of four wheels or six wheels, according to the length and
weight of the carriage to be supported.
[Illustration: Fig. 39, 40, 41, 42]
Figs. 39, 40, and 41 show sketch elevation, plan, and transverse 56
section of one pattern of four-wheel bogie truck largely adopted in
American carriage stock, and although there are other types varying in
detail, the general principle remains the same in all. The diagram
sketch (Fig. 42) represents the two bogie trucks slightly swivelled to
adapt themselves to the curve round which the carriage is supposed to
be passing.
For carriage or waggon stock with an independent bogie truck at each
end, the central pivot and swivelling motion supply all the freedom
that is requisite; but for locomotives it is necessary to provide for
lateral as well as for swivelling movement. The driving and trailing
wheels--and sometimes one or two other pairs of wheels--work rigidly
in the frames, and as the normal position of the centre of the bogie
truck must be in the centre line of the engine for the straight line,
it is evident that some appliance must be introduced to allow the
truck to move laterally when the engine has to traverse the curves.
Figs. 43, 44, and 45 give sketch elevation, plan, and transverse
section of a swing-link bogie truck as applied to an ordinary American
locomotive. Its recommendations are its simplicity, its efficiency,
and its accessibility for inspection and lubrication. The swing-links,
which provide for the lateral movement, are direct acting, and do not
require any side springs of steel or indiarubber. All the principal
parts of the bogie are visible and not mysteriously cased in with
plate-iron boxwork.
In the sketches several minor details are purposely omitted and only
sufficient particulars shown to explain the method of working. The
under side of the upper centre plate which carries the cylinder
castings and smoke-box end of boiler is cup-shaped, and fits into an
annular groove or channel in the lower centre plate, which is
suspended from the framework of the truck by the four swinging links.
Practically the entire carrying and swivelling work of the bogie truck
is effected by the annular-groove casting moving round the cup-shaped
casting, and the centre pin is merely passed down through each to
guard against the risk of the one lifting out of the other from sudden
shock or derailment.
[Illustration: Fig. 43, 44, 45, 46]
The lateral movement of the truck is obtained by means of the four
swing-links. When the engine is on the straight road the centre line
of the bogie is on the centre line of the engine, and the links hang
in the positions shown on the sketch, inclined towards the centre; but 58
upon entering a curve they come into play, and allow the truck to move
out sideways to the right or left, according to the direction of the
curve, the one pair of links assuming a flatter angle, while the other
pair approach nearer to the vertical, the extent of side movement
depending on the amount of the curvature. When the engine enters the
straight line again, the bogie truck resumes its central position.
The Bissell truck consists of one pair of wheels connected to a
triangular framework, as shown in Fig. 46. The axle-boxes are attached
to the side of the triangle which lies parallel to the axle, the other
two sides terminate in a circular ring which works round a centre pin
fixed to the engine. These two sides are practically the radii of a
given circle, and permit a large amount of lateral movement, which can
be controlled by placing suitable stop-pieces to limit the side play
to the extent desired.
Radial axle-boxes have been tried on the engines of some railways. In
the best types the opposite boxes are braced together by a diaphragm,
or plate-iron framework, to ensure that both boxes work together. The
curved faces of the horn-blocks, in which the radial axle-boxes slide,
are struck from a centre taken at some point to the rear of the normal
centre line of the axle, and stops are placed at proper distances to
control the extent of lateral movement. Although the advocates of
radial axle-boxes may urge some points in their favour, there are few
engineers, if any, amongst those who have had practical experience of
both systems, who would for a moment claim for the radial axle-box
anything but a modicum of the many advantages obtained by the
four-wheeled bogie truck.
As one of the principal functions of a four-wheeled bogie truck for an
engine is to act as a path-finder, or guide, to the other wheels which
constitute the fixed or rigid wheel-base portion of the machine, it
follows, therefore, that the full benefit of the bogie truck can only
be obtained when it is placed at the leading, or front, end of the
engine. In this position the bogie, with its swivelling arrangement
and smaller weights, is the first to pass over the rails, and in doing
so shapes the course and prepares the way for the easy running of the
heavier wheel weights which have to follow. When the bogie truck is
placed at the rear end of the engine, its action is restricted to
affording lateral movement only, and the driving and coupled wheels
have to force or pound themselves round the curves in a jerky,
irregular manner, as compared to their smooth running when following 59
the leading or guiding influence of a bogie truck in front.
The wheel-base of a four-wheeled bogie truck for an engine should
always be greater than the gauge of the line over which the bogie has
to travel On the 4 feet 8½ inch gauge some of the best results have
been obtained with bogies having wheel-bases varying from 6 feet to 7
feet. Where the wheel-centres have been less than 6 feet, the running
has been found to be much less steady than with the wider spacing; and
where the wheel-base is not more than the gauge, there is a tendency
for the bogie to catch, or lock, when passing round sharp curves.