! Rails, Rail
Systems, Railroads and Railways
Modern railway systems came only after large
quantities of iron and steel products became available. These products made
possible the rails, steam locomotives,
and all the other railway system parts.
Iron and steel also made possible the large
ships that replaced wooden ships that allowed European expansion to the rest of
the world. The railroads however were the first major development in land
transport since animals had replaced men to carry burdens and provide draft for
sledges and wagons
Much of what we accept as normal in modern
living depends on the communication and distribution that followed from the
development of canals and railroads. Modern highways and their civil
engineering are direct descendents of the technology developed for railways.
The pioneer Railway in
Railways reached their peak in
Any student of transportation and urban
development can learn a great deal about potential and possible future systems
by understanding the technology, evolution and role of the railroads. This note
briefly explores some aspects of this topic. Many rural centers owe their
location to the service requirements of locomotives and track.
Some of the earliest railways were used in
mines to carry the heavy loads. The motive power was men and animals. The
rolling resistance of a relatively large diameter wheel is much lower than two
surfaces sliding over each other or of a small diameter roller. When a hard
smooth wheel rolls on a hard smooth surface the resistance is further reduced.
Contemporary smooth steel tires on smooth steel rails or other surfaces
approach the lower limits of rolling resistance. This is utilized in ball and
roller bearings.
The evolution of wheel systems and their
manufacture is one of humanity's major accomplishments. Providing wheels with
durable tires and low axle friction greatly reduces the effort required to move
a supported load. An assembly of four wheels provides basic vehicle stability.
Put these on a prepared track composed of two parallel rails and you have a railroad.
The virtues of the railroad idea were known
and used before steam and other traction engines were developed. Early
railroads, especially in urban areas (trams) used horses as
the motive power. Later trams used electric traction
motors. Some used underground cables driven from central stations. The most
famous cable car system still in use is in
The real potential of a railroad followed
development of steam powered locomotives. In 1803
Richard Trevithick, a British engineer built a Steam
Locomotive for use in a mine.
A railroad is composed of a variety of
components and is good example of a system.
Brief reflection reveals that the several parts of such a system have to be
carefully coordinated to obtain optimal performance. The harder and stronger
the wheel and rail surfaces are the lower the deformation of the contact area
and the lower the rolling resistance. Steel provides a nearly ideal material.
Iron and steel had been known for millennia
but not at affordable prices. They were used for tools and weapons. For
railways to be practical the iron and steel had to be available in large
quantities for relatively low prices.
Once the basic idea is grasped then working
out the detailed shapes and material characteristics became major tasks. The
low rolling resistances invite not only heavy loads but also higher speeds. Low
rolling resistance works both ways. Once a mass is moving it will only be
slowed down by the various resistances inhibit motion. Effective Vehicle Motive Power and Braking is necessary.
Land transport speeds had been limited by the
'running' speed of persons or animals. Horses and Coaches
were the best compromise for speed and durability for most transport at the
time the railways began to expand.
Mining provided the impetus for a practical
replacement for the animal, wind, and waterpower that were in use for pumping.
In a relatively short period of time steam power developed from the early
pumping engines. These are also based on iron and the technology used to make
cannon. Making a steam powered traction engine was the next step in the
development of the basic ingredients of a railway system.
Steam power for boats on North America began
in 1807 with
The steam is a means of converting and
storing the energy from combustion in a form that can be used in an engine.
Linear motion steam engines were first used for
pumping. Rotary motion engines came later. Direct
internal use of the combustion products in an engine for mechanical motion also
came later.
A tricky part of steam power is the safe
production of the required steam. The boiler is usually a fairly large
pressure vessel. Steam expands a great deal when the pressure is reduced. This
characteristic is used to transform a small quantity of steam under pressure
into mechanical motion by the engine. If the pressure is suddenly released by a
component pressure failure, a catastrophic explosion results. Many disastrous
steam explosions occurred in the early equipment.
James Watt was one of the earliest steam
engine builders'. His original engines were used in mines and other
'stationary' applications. The historic 1807 steamboat Clermont
that plied the Hudson River in
The first public carrier railroad,
the Stockton & Darlington' in
The first railroad in
The Champlain and
The
The first Canadian line to use all iron rails
hauled coal from the Albion Mine in Stellarton to
Steel wheels on steel rails have very low
rolling resistance but fairly high sliding friction or 'adhesion' between the
surfaces. This allows development of
traction and braking forces between wheels and track. Large diameter relatively
heavily loaded wheels evolve as optimal solutions for low speed reciprocating
traction engines.
Stephenson's Rocket
was a clever exploitation of these ideas to increase speed. From it and other
designs evolved the once familiar steam railway locomotive. These historically
provided a major increase in travel speeds.
The 'Rocket' has an externally mounted single
cylinder driving a large wheel on each side. The boiler is mounted above the
driving wheels. The driver and fireman are behind the boiler. The fuel and
water supply for the boiler is carried on a separate vehicle (the tender)
behind the locomotive. This is the essential layout that leads to the steam locomotives that reigned from the 1840's to the
1950's.
These locomotives consumed copious quantities
of fuel and even larger quantities of water. The exhaust steam
was used to induce draft to aid combustion. Hotter fires reduced the size of
the combustion chamber needed to keep a steady supply of steam. The fuel of
choice became high heat, low price coal. Only near the end of steam
power was the more convenient oil used for heat.
The smooth rails produced a relatively
smooth ride. When the ride in a railway is compared with that of the
contemporary wagons and coaches, the improvement was spectacular. The only
bump that was left was the rail joints and any imperfections in rail or wheels.
The rail joint bumps have been overcome with continuous welded rails. Smooth
fast rides lead to the demand for longer trips.
The demand for water, fuel and the manpower
to feed the boiler requires strategic depots along an extended railway. The
major requirement is for water, and the next for manpower. Shoveling the
required coal in the time it takes to cover distance at desirable speeds and
grade climbing is rigorous work.
Crew changes at about 125 mile intervals became an operating
rule that lead to the establishment of communities along the line.
These and the manpower and depots required for track maintenance provided the
basic settlement structure required for railroads in undeveloped areas. Before
the railroads depots at were required at closer intervals for changes of
runners, or animals for high speed travel and communication.
The low rolling resistance leads to long 'trains' of 'wagons' or 'cars'. Manpower
is required to change 'switches' when more than one route or train is operated.
Manpower operated the brakes in the early trains. The train crew
composed of brakemen later trainmen became separate from the engine
crew. The train crew came to include the conductor who was
the crew chief. On passenger trains space was provided for this crew in the
passenger cars. On freight trains they traveled in the van or caboose at
the rear end.
The other labour requirement is track
maintenance. Track quality must be maintained to avoid costly derailments.
Optimizing travel and work time of inspection and maintenance personnel
requires systematic depots and settlements that are more closely spaced than
for operating crew.
Besides the operating and track crews there
are station and administrative personnel
requirements. The developing railways also required construction crews to
extend the track and other fixed plant including the communications and
signaling systems. Telegraph lines paralleling rail lines were a very early
addition to the railroad system for communication purposes. The
surplus capacity of these telegraph lines led to the railways getting into the
communication business.
The tractive effort of a railway locomotive
is used to overcome the rolling and grade resistance of the train of cars that
normally carry the load. Railway trains tend to have low power to mass ratios.
This means that there is little reserve power to accelerate or overcome grade
resistance. Where heavy grades are encountered the solution has been to use a
number of locomotives. Ideally these are distributed along the length of the
train.
On nearly level terrain there is very little
grade resistance and a large load can be moved by a small tractive effort using
railroad technology. Railway location tends to be a compromise between low
grades, short point to point distance and sufficient radius curves to maintain
speed.
Steep grades or rapid acceleration require
large tractive effort. Urban rail transit systems tend to distribute the
tractive effort along the length of a train by powering one or more axles of
each car. For maximum performance this leads to powering every wheel. Urban
transit requires short travel times for relatively short distances. Acceleration
and deceleration tolerance provides the limits to minimizing travel times.
These limits are usually determined for standing passengers at three or four
miles per hour per second,
Development of transport technology generally
favors increasing speed for person travel. When a superior, i.e. higher
speed technology appears, the low speed ones are usually regulated to
goods movements. This is partly because increased speed usually is accompanied
by an increase in energy and other resource consumption per unit distance.
Desirable 'Railway' grades, speeds and
'keeping the train on the track' require precision route alignment.
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End to date: 051217, ams