ROAD AND RAIL.
The existing keen motor-car rivalry presents one of the most
interesting and instructive mechanical problems which are left still
unsolved by the close of the nineteenth century. The question to be
determined is not so much whether road locomotion by means of
mechanical power is practicable and useful, for, of course, that point
has been settled long ago; indeed it would have been recognised as
settled years before had it not been for the crass legislation of a
quarter of a century since which deliberately drove the first
steam-motors off the road in order to ensure the undisturbed supremacy
of horse traffic. The real point at issue is whether a motor can be
made which shall furnish power for purposes of road locomotion as
cheaply and conveniently as is already done for stationary purposes.
Horse traction, although extremely dear, possesses one qualification
which until the present day has enabled it to outdistance its
mechanical competitors upon ordinary roads. This is its power of
adapting itself, by special effort, to the exigencies caused by the
varying nature of the road. Watch a team of horses pulling a waggon
along an undulating highway, with level stretches of easy going and
here and there a decline or a steep hill. There is a continual
adjustment of the strain which each animal puts upon itself according
to the character of the difficulties which must be surmounted, the
effort varying from nothing at all--when going down a gentle
decline--up to the almost desperate jerk with which the vehicle is
taken over some stony part right on the brow of an eminence. The whip
cracks and by threats and encouragements the driver induces each horse
to put forth, for one brief moment, an effort which could not be
sustained for many minutes save at the peril of utter exhaustion.
When the unit of nominal horse-power was fixed at 33,000 foot-pounds
per minute the work contemplated in the arbitrary standard was
supposed to be such as a horse could go on performing for several
hours. It was, of course, well recognised that any good, upstanding
horse, if urged to a special effort, could perform several times the
indicated amount of work in a minute.
Nevertheless the habit of reckoning steam-power in terms of a unit
drawn from the analogy of the horse undoubtedly tended for many years
to obscure the essential difference between the natures of the two
sources of power. Railroads were built with the object of rendering as
uniform as possible the amount of power required to transport a given
weight of goods or passengers over a specified distance; and
consequently the application of the steam-engine to traffic conducted
on the railway line was a success. Many inventors at once jumped to
the conclusion that, by making some fixed allowance for the greater
roughness of an ordinary road, they would be able to construct a
steam-traction engine that would suit exactly for road traffic. In a
rough and rudimentary way an attempt to provide for the special effort
required at steep or stony places was made by the introduction of a
kind of fly-wheel of extraordinary weight proportionate to the size of
the engine; and the same object was aimed at by increasing the power
of the engine to somewhere near the limit of the possible special
requirements. The consequence was the evolution of an immensely
ponderous and wasteful machine, which for some years only held its
ground within the domain of the heavy work of roadmaking. As a means
of road traction the steam-engine was for half a century almost
entirely discomfited and routed by horse-power, partly owing to this
mechanical defect and partly, as we have seen, through legislative
partisanship.
The explosive type of engine was next called into requisition to do
battle against the living competitor of the engineer's handiwork.
Petroleum and alcohol, when volatilised and mixed with air in due
proportion, form explosive mixtures which are much more nearly
instantaneous in their action than an elastic vapour like steam held
under pressure in a boiler, and liberated to perform its work by
comparatively slow expansion. The petroleum engine, as applied to the
automobile, does its work in a series of jerks which provide for the
unequal degrees of power required to cope with the unevenness of a
road.
As against this, however, there are certain grave defects, due mainly
to the use of highly inflammable oils vapourised at high temperatures;
and these have impressed a large proportion of engineers with a belief
that, in the long run, either electricity or steam will win the day.
Storage batteries are well adapted for meeting the exigencies of the
road, just as they are for those of tramway traffic, because, as soon
as an extra strain is to be met, there is always the resource of
coupling up fresh batteries held in reserve--a process which amounts
to the same as yoking new horses to the vehicle in order to take it up
a hill. In practice, however, it is found that the jerky vibratory
motion of the gasoline automobile provides for this in a way almost as
convenient, although not so pleasant.
The chance of the steam-engine being largely adopted for automobile
work and for road traffic generally depends principally on the
prospects of inventing a form of cylinder--or its equivalent--which
will enable the driver to couple up fresh effective working parts of
his machinery at will, just as may be done with storage batteries. A
new form of steam cylinder designed to provide for this need will
outwardly resemble a long pipe--one being fixed on each lower side of
the vehicle--but inwardly it will be divided into compartments each of
which will have its own separate piston. Practically there will thus
be a series of cylinders having one piston-rod running through them
all, but each having its own piston.
Normally, this machine will run with an admission of steam to only one
or two of the cylinders; but when extra work has to be done the other
cylinders will be called into requisition by the opening of the steam
valves leading to them. Provision can be made for the automatic
working of this adjustment by the introduction of a spring upon the
piston-rod, so arranged that, as soon as the resistance reaches a
certain point, a lever is actuated which opens the valves to admit
steam to the reserve cylinders of the engine. On such occasions, of
course, the consumption of steam must necessarily be greatly
increased; but on the other hand the automatic system of the admission
to each cylinder also results in a shutting off of the steam when
little or no work is required. In fact, with a fully automatic action,
regulating the consumption of steam exactly according to the amount of
force necessary to drive the automobile, it would be possible to work
even a single cylinder to much greater advantage than is done by the
machines generally in use.
So heavy are the storage batteries needed for electric traction of the
road motor-car that practically it is not found convenient to carry
enough of cells to last for more than a twenty-mile run. The batteries
must then either be replaced, or a delay of some three hours must
occur while they are being recharged. The idea of establishing
charging stations at almost every conceivable terminus of a run is
quite chimerical; and, even if hundreds of such stations were
provided for the convenience of the users of electric traction, the
limitation imposed by being forced to follow the established routes
would always give to the non-electric motor an advantage over its
competitor.
The best hope for the storage battery on the automobile rests upon its
convenience as a repository of reserve power in conjunction with such
a prime motor as the steam-engine. A turbine worked by a jet of steam,
as already described, and moving in a magnetic field to generate
electricity for storage in a few cells, is a convenient form in which
steam and electricity can be yoked together in order to secure a power
of just the type suitable for driving an automobile. In the machine
indicated the supply of the motive power is direct from the storage
batteries, which can be coupled up in any required number according to
the exigencies of the road. Automatic gear may be introduced by an
adaptation of the principle already referred to.
In a light road-motor for carrying one or two persons on holiday trips
or business rounds, the quality of adaptability of the source of power
to the sudden demands due to differences of level in the road is not
so absolutely essential as it is in traction engines designed for the
transport of goods over ordinary roads. In the former class of work
the waste of power involved in employing a motor of strength
sufficient to climb hills--although the bulk of the distance to be
travelled is along level roads--may not be at all so serious as to
overbalance the many and manifest advantages of the automobile
principle. At the same time, as has already been indicated, there is
no doubt whatever that when proper automatic shut-off contrivances
have been applied for economising mechanical energy in the passenger
road-motor, an immense impetus will be given to its advancement.
In the road traction-engine the need for what may be termed _effort_
on the part of the mechanism is much greater, more especially as the
competition against horse-traction is conducted on terms so much more
nearly level. A team of strong draught-horses driven by one man on a
well-loaded waggon is a far more economical installation of power than
a two-horse buggy carrying one or two passengers.
The asphalt and macadamised tracks which are now being laid down along
the sides of roads for the convenience of cyclists, are the
significant forerunners of an improvement destined to produce a
revolution in road traffic during the twentieth century. When
automobiles have become very much more numerous, and local
authorities find that the settlement of wealthy or comparatively
well-to-do families in their neighbourhoods may depend very largely
upon the question whether light road-motor traffic may be conveniently
conducted to and from the nearest city, an immense impetus will be
administered to the reasonable efforts made for catering for the
demand for tracks for the accommodation of automobiles, both private
and public.
The tyranny of the railway station will then be to a large extent
mitigated, and suburban or country residents will no longer be
practically compelled to crowd up close to each station on their lines
of railroad. Under existing conditions many of those who travel
fifteen or twenty miles to business every day live just as close to
one another, and with nearly as marked a lack of space for lawn and
garden, as if they lived within the city. The bunchy nature of
settlement promoted by railways must have excited the notice of any
intelligent observer during the past twenty or thirty years--that is
to say since the suburban railroad began to take its place as an
important factor in determining the locating of population.
To a very large extent the automobile will be rather a feeder to the
railway than a rival to it; and all sorts of by-roads and country
lanes will be improved and adapted so as to admit of residents running
into their stations by their own motor-cars and then completing their
journeys by rail. But when this point has been reached, and when
fairly smooth tracks adapted for automobile and cycling traffic have
been laid down all over the country, a very interesting question will
crop up having reference to the practicability of converting these
tracks into highways combining the capabilities both of roads and of
railways.
In an ordinary railroad the functions of the iron or steel rails are
twofold, first to carry the weight of the load, and second to guide
the engine, carriage or truck in the right direction. Now the latter
purpose--in the case of a rail-track never used for high speeds,
especially in going round curves--might be served by the adoption of a
very much lighter weight of rail, if only the carrying of the load
could be otherwise provided for. In fact, if pneumatic-tyre wheels,
running on a fairly smooth asphalt track, were employed to bear the
weight of a vehicle, there would then be no need for more than one
guide-rail, which might readily be fixed in the middle of the track;
but this should preferably be made to resemble the rail of a tram
rather than that of a railroad.
"Every man his own engine-driver" will be a rule which will
undoubtedly require some little social and mechanical adjustment to
carry out within the limits of the public safety. But the automobile,
even in its existing form, makes the task of completing this
adjustment practically a certainty of the near future; and as soon as
it is seen that motor tracks with guide lines render traffic safer
than it is on ordinary roads, the main objections to the innovation
will be rapidly overcome. The rule of the road for such guide-line
tracks will probably be based very closely on that which at present
exists for ordinary thoroughfares. On those roads where two tracks
have been laid down each motor will be required to keep to the left,
and when a traveller coming up behind is impatient at the slow rate of
speed adopted by his precursor he will be compelled to make the
necessary detour himself, passing into the middle of the thoroughfare
and there outstripping the party in front, without the assistance of
the guide-rail, and rejoining the track.
To execute this movement, of course, the motor wheels for the
guide-tracks must be mounted on entirely different principles from
those adapted for railroad traffic. The broad and soft tyred wheels
which bear upon the asphalt track will be entrusted with the duty of
carrying the machine without extraneous aid; but there will be two
extra wheels, one in front and one at the rear, capable of being
lifted at any time by means of a lever controlled by the driver. These
guiding wheels will fit into the groove of the tram line in the
centre, being made of a shape suitable for enabling the driver to pick
up the groove quickly whenever he pleases. The carrying wheels of the
vehicle in this system are enabled to pass over the guide-rail
readily, because the latter does not stand up from the track like the
line in a railroad.
A simpler plan, particularly adapted for roads which are to have only
a single guide-rail, is to place the rail at the off-side of the
track, and to raise it a few inches from the ground. The wheels for
the rail are attached to arms which can be raised and lifted off the
rail by the driver operating a lever. Guiding irons, forming an
inverted Y, are placed below the bearings of the wheels to facilitate
the picking up of the rail, their effect being that, if the driver
places his vehicle in approximately the position for engaging the side
wheels with the rail and then goes slowly ahead, he will very quickly
be drawn into the correct alignment. Of course the rails for this kind
of track can be very light and inexpensive in comparison with those
required for railroads on which the whole weight of each vehicle, as
well as the lateral strain caused by its guidance, must fall upon the
rail itself.
The asphalt track and its equivalent will be the means of bringing
much nearer to fulfilment the dream of having "a railway to every
man's door". Many such tracks will be equipped with electric cables as
well as guiding-rails, so that cars with electric motors will be
available for running on them, and the power will be supplied from a
publicly-maintained station. Some difficulty may at first be
experienced in adjusting the rates and modes of payment for the
facilities thus offered; but a convenient precedent is present to hand
in the class of enactment under which tramway companies are at present
protected from having their permanent ways used by vehicles owned by
other persons. Practically the possession of a vehicle having a
flanged wheel and a gauge exactly the same as that of the tram lines
in the vicinity may be taken to indicate an intention to use the
lines. Similarly a certain relation between the positions of guiding
wheels and those of the connections with cables may be held to furnish
evidence of liability to contribute towards the maintenance of
motor-tracks.
Roads and railways will be much more closely inter-related in the
future than they have been in the past. The competition of the
automobile would in itself be practically sufficient to force the
owners of railways into a more adaptive mood in regard to the true
relations between the world's great highways. The way in which the
course of evolution will work the problem out may be indicated
thus:--First, the owners of automobiles will find it convenient in
many instances to run by road to the nearest railway station which
suits their purposes, leaving their machines in charge of the
stationmaster and going on by train. In course of time the owners of
"omnibus automobiles" will desire to secure the same advantage for
their customers, and on this account the road cars will await the
arrival and departure of every train just as horse vehicles do at
present. The next step will be taken by the railway companies, or by
the local authorities, when it becomes obvious that there is much more
profit in motor traffic than there ever was in catering for the public
by means of vehicles drawn by horses. Each important railway station
will have its diverging lines of motor-traffic for the convenience of
passengers, some of them owned and managed by the same authority as
the railway line itself.
Rivalry will shortly enforce an improvement upon this system, because
in the keen competition between railway lines those stations will
attract the best parts of the trade at which the passengers are put to
the smallest amount of inconvenience. The necessity for changing
trains, with its attendant bustle of looking after luggage, perhaps
during very inclement weather, always acts as a hindrance to the
popularity of a line. When "motor-omnibuses" are running by road all
the way into the city, setting people down almost at their doors and
making wide circuits by road, the proprietors of these vehicles will
make the most of their advantages in offering to travellers a cosy and
comfortable retreat during the whole of their journey.
Road-motors, comfortably furnished, will therefore be mounted upon low
railway trucks of special construction, designed to permit of their
being run on and off the trucks from the level of the ground. The plan
of mounting a road vehicle upon a truck suited to receive it has
already been adopted for some purposes, notably for the removal of
furniture and similar goods; and it is capable of immense extension.
An express train will run through on the leading routes from which
roads branch out in all directions, and as it approaches each station
it will uncouple the truck and "motor-omnibus" intended for that
destination. The latter will be shunted on to a loopline. The
road-motor will be set free from its truck and will then proceed on
its journey by road.
When a similar system has been fully adapted for the conveyance of
goods by rail and road experiments will then be commenced, on a
systematic basis, with the object of rendering possible the picking up
of packages, and even of vehicles, without stopping the train. The
most pressing problem which now awaits solution in the railway world
is how to serve roadside stations by express trains. "Through"
passengers demand a rapid service; while the roadside traffic goes
largely to the line that offers the most frequent trains. In the
violent strain and effort to combine these two desiderata the most
successful means yet adopted have been those which rely upon the
destruction of enormous quantities of costly engine-power by means of
quick-acting brakes. The amount of power daily converted into the
mischievous heat of friction by the brakes on some lines of railway
would suffice to work the whole of the traffic several times over; but
the sacrifice has been enforced by the public demand for a train that
shall run fast and shall yet stop as frequently as possible.
Progress in this direction has reached its limit. A brake that shall
conserve, instead of destroying, the power of the train's inertia on
pulling up at a station is urgently required; but the efforts towards
supplying the want have not, so far, proved very successful. Each
carriage or truck must be fitted with an air-pump so arranged that, on
the application of the brake by the engine-driver, it shall drive back
a corresponding amount of air to that which has been liberated from
the reservoir, and the energy thus stored must be rendered available
for re-starting the train. Trials in this direction have been made
through the application of strong springs which are caused to engage
upon the wheels when the brake is applied, and thus are wound up, but
which may then be reversed in position, so that for the starting of
the vehicle the rebound of the spring offers material assistance. It
is obvious, however, that the use of compressed air harmonises better
with the railway system than any plan depending upon springs. The
potential elasticity in an air-reservoir of portable dimensions is
enormously greater than that of any metallic spring which could
conveniently be carried.
In picking up and setting down mail-bags a system has been for some
years in operation on certain railway lines indicating in a small way
the possibilities of the future in the direction of obviating the need
for stopping trains at stations. The bag is hung on a sliding rod
outside of the platform, and on a corresponding part of the van is
affixed a strong net, which comes in contact with the bag and catches
it while the train goes past at full speed. Dropping a bag is, of
course, a simpler matter.
The occasionally urgent demand for the sending of parcels in a similar
manner has set many inventive brains to work on the problem of
extending the possibilities of this system, and there seems no reason
to doubt that before long it will be practicable to load some classes
of small, and not readily broken, articles into trucks or vans while
trains are in motion.
The root idea from which such an invention will spring may be borrowed
from the sliding rail and tobogganing devices already introduced in
pleasure grounds for the amusement of those who enjoy trying every
novel excitement. A light and very small truck may be caused to run
down an incline and to throw itself into one of the trucks comprising
a goods train. The method of timing the descent, of course, will only
be definitely ascertained after careful calculation and experiments
designed to determine what length of time must elapse between the
liberation of the small descending truck and the passing of the
vehicle into which its contents are to be projected.
Foot-bridges over railway lines at wayside stations will afford the
first conveniences to serve as tentative appliances for the purpose
indicated. From the overway of the bridge are built out two light
frameworks carrying small tram-lines which are set at sharp
declivities in the directions of the up and the down trains
respectively, and which terminate at a point just high enough to clear
the smoke-stack of the engine.
The small truck, into which the goods to be loaded are stowed with
suitable packings to prevent undue concussion, is held at the top of
its course by a catch, readily released by pressure on a lever from
below. The guard's van is provided at its front end with a steel,
upright rod carrying a cross-piece, which is easily elevated by the
guard or his assistant in anticipation of passing any station where
parcels are to be received by projection. At the rear of the van is an
open receptacle communicating by a door or window with the van itself.
At the instant when the steel cross-piece comes in contact with the
lever of the catch, which holds the little truck in position on the
elevated footbridge, the descent begins, and by the time that the
receptacle behind the van has come directly under the end of the
sloping track the truck has reached the latter point and is brought to
a sudden standstill by buffers at the termination of the miniature
"toboggan". The ends of the little truck being left open, its contents
are discharged into the receptacle behind the van, from which the
guard or assistant in charge removes them into the vehicle itself. For
catching the parcels thrown out from the van a much simpler set of
apparatus is sufficient.
On a larger scale, no doubt in course of time, a somewhat similar plan
will be brought into operation for causing loaded trucks to run from
elevated sidings and to join themselves on to trains in motion. One
essential condition for the attainment of this object is that the
rails of the siding should be set at such a steep declivity that, when
the last van of the passing train has cleared the points and set the
waiting truck in motion by liberating its catch, the rate of speed
attained by the pursuing vehicle should be sufficiently high to enable
it to catch the train by its own impetus.
It may be found more convenient on some lines to provide nearly level
sidings and to impart the necessary momentum to the waiting truck,
partly through the propelling agency of compressed air. Any project
for what will be described as "shooting a truck loaded with valuable
goods after the retreating end of a train," in order to cause it to
catch up with the moving vehicles, will no doubt give rise to alarm;
and this feeling will be intensified when further proposals for
projecting carriages full of passengers in a similar method come up
for discussion. But these apprehensions will be met and answered in
the light of the fact that in the earlier part of the nineteenth
century critics of what was called "Stephenson's mad scheme" of making
trains run twenty or even thirty miles an hour were gradually induced
to calm their nerves sufficiently to try the new experience of a train
journey!
The wire-rope tramway has hitherto been used principally in connection
with mines situated in very hilly localities. Trestles are erected at
intervals upon which a strong steel rope is stretched and this carries
the buckets or trucks slung on pulley-blocks, contrived so as to pass
the supports without interference. A system of this kind can be worked
electrically, the wire-rope being employed also for the conveyance of
the current. But an inherent defect in the principle lies in the fact
that the wire-rope dips deeply when the weight passes over it, and
thus the progress from one support to another resolves itself into a
series of sharp descents, followed by equally sharp ascents up a
corresponding incline. The usual way of working the traffic is to haul
the freight by means of a rope wound round a windlass driven by a
stationary engine at the end. The constantly varying strain on the
cable proves how large is the amount of power that must be wasted in
jerking the buckets up one incline to let them jolt down another when
the point of support has been passed.
Hitherto the wire-rope tramway has been usually adopted merely as
presenting the lesser of two evils. If the nature of the hills to be
traversed be so precipitous that ruinous cuttings and bridges would be
needed for the construction of an ordinary railway or tramway line,
the idea of conveyance by wire suggests itself as being, at least, a
temporary mode of getting over the difficulty. But a great extension
of the principle of overhead haulage may be expected as soon as the
dipping of the load has been obviated, and the portion of the moving
line upon which it is situated has been made rigid. A strong but light
steel framework, placed in the line of the drawing-cable, and of
sufficient length to reach across two of the intervals between the
supports, may be drawn over enlarged pulleys and remain quite rigid
all the time.
The weight-carrying wire-rope is thus dispensed with, and the
installation acquires a new character, becoming, in point of fact, a
moving bridge which is drawn across its supports and fits into the
grooves in the wheels surmounting the latter. The carriage or truck
may be constructed on the plan adopted for the building of the longest
type of modern bogie carriages for ordinary railways, the tensile
strength of steel rods being largely utilised for imparting rigidity.
We now find that instead of a railway we have the idea of what may be
more appropriately called a "wheelway". The primitive application of
the same principle is to be seen in the devices used in dockyards and
workshops for moving heavy weights along the ground by skidding them
on rollers. Practically the main precaution observed in carrying out
this operation is the taking care that no two rollers are put so far
apart that the centre of gravity of the object to be conveyed shall
have passed over one before the end has come in contact with the next
just ahead of it.
The "wheelway" itself will be economical in proportion as the length
of the rigid carriage or truck which runs upon it is increased. The
carrying of cheap freight will be the special province of the
apparatus, and it will therefore be an object to secure the form of
truck which will give, with the least expense, the greatest degree of
rigidity over the longest stretch of span from one support to another.
Some modification of the tubular principle will probably supply the
most promising form for the purpose. The hope of this will be greatly
enhanced through the recent advances in the art of tube-constructing
by which wrought-iron and tough steel tubes can be made quite seamless
and jointless, being practically forged at one operation in the
required tubular shape.
For mining and other similar purposes, the long tubal "wheelway"
trucks of this description can be drawn up an incline at the loading
station so as to be partially "up-ended" in position for receiving the
charges or loads of mineral or other freight. After this they can be
despatched along the "wheelway" on the closing of the door at the
loading end. In regard to the mode of application of the power in
traction, the shorter-distance lines may serve their objects well
enough by adopting the endless wire-rope system at present used on
many mining properties.
But it is found in practice that for heavy freight this endless cable
traction does not suit over distances of more than about two miles.
Mining men insist upon the caution that where this length of distance
has to be exceeded in the haulage of ore from the mine over wire-rope
tramways, there is need for two installations, the loaded trucks being
passed along from one to the other by means of suitable appliances at
the termini.
Electric traction must, in the near future, displace such a cumbrous
system, and the plan upon which it will be applied will probably
depend upon the use of a steel cable along which the motor-truck must
haul itself in its progress. This cable will be kept stationary, but
gripped by the wheels and other appliances of the electric motors with
which the long trucks are provided. Besides this there must also be
the conducting cables for the conveyance of the electric current.
For cheap means of transport in sparsely-developed country, as well as
in regions of an exceptionally hilly contour, the "wheelway" has a
great future before it. Ultimately the system can be worked out so as
to present an almost exact converse of the railway. The rails are
fixed on the lower part of the elongated truck, one on each side;
while the wheels, placed at intervals upon suitable supports,
constitute the permanent way. The amount of constructional work
required for each mile of track under this plan is a mere fraction of
that which is needed for the permanent way and rolling stock of a
railway, the almost entire absence of earth-works being, of course, a
most important source of economy.
Probably the development of transport on the principles indicated by
the evolution of the ropeway or wire-rope tramway will take place
primarily in connection with mining properties, and for general
transport purposes in country of a nature which renders it unsuitable
for railway construction. This applies not merely to hilly regions,
but particularly to those long stretches of sandy country which impede
the transport of traffic in many rich mining regions, and in patches
separating good country from the seaboard. In the "wheelway" for land
of this character the wheels need not be elevated more than a very few
feet above the ground, just enough to keep them clear of the drift
sand which in some places is fatal to the carrying out of any ordinary
railway project.
The conception of a truck or other vehicle that shall practically
carry its own rail-road has been an attractive one to some inventive
minds. In sandy regions, and in other places where a railway track is
difficult to maintain, and where, at any rate, there would hardly be
sufficient traffic to encourage expenditure in laying an iron road, a
very great boon would be a kind of motor which would lay its own rails
in front of its wheels and pick them up again as soon as they had
passed.
A carriage of this kind was worked for some time on the Landes in
France. The track was virtually a kind of endless band which ran round
the four wheels, bearing a close resemblance to the ramp upon which
the horse is made to tread in the "box" type of horse-gear. Several
somewhat similar devices have been brought out, and a gradual approach
seems to have been made towards a serviceable vehicle.
A large wheel offers less resistance to the traction of the weight
upon it than a small one. The principal reason for this is that its
outer periphery, being at any particular point comparatively straight,
does not dip down into every hollow of the road, but strikes an
average of the depressions and prominences which it meets. The
pneumatic tyre accomplishes the same object, although in a different
way, the weight being supported by an elastic surface which fits into
the contour of the ground beneath it; and the downward pressure being
balanced by the sum total of all the resistant forces offered by every
part of the tyre which touches the ground, whether resting on hollows
or on prominences.
Careful tests which have been made with pneumatic-tyred vehicles by
means of various types of dynamometer have proved that, altogether
apart from the question of comfort arising from absence of vibration,
there is a very true and real saving of actual power in the driving of
a vehicle on wheels fitted with inflated tubes, as compared with the
quantity that is required to propel the same vehicle when resting on
wheels having hard unyielding rims. So far as cycles and motor-cars
are concerned, this is the best solution of the problem of averaging
the inequalities of a road that has yet been presented; but when we
come to consider the making of provision for goods traffic carried by
traction engines along ordinary roadways, the difficulties which
present themselves militating against the adoption of the pneumatic
principle--at any rate so long as a cheap substitute for india-rubber
is undiscovered--are practically insurmountable.
Large cart wheels of the ordinary type are much more difficult to
construct than small ones, besides being more liable to get out of
order. The advantages of a large over a small wheel in reducing the
amount of resistance offered by rough roads have long been
recognised, and the limit of height was soon attained. In looking for
improvement in this direction, therefore, we must inquire what new
types of wheel may be suggested, and whether an intermediate plan
between the endless band, as already referred to, and the
old-fashioned large wheel may not find a useful place.
Let the wheel consist of a very small truck-wheel running on the
inside of a large, rigid steel hoop. The latter must be supported, to
keep it from falling to either side, by means of a steel semi-circular
framework rising from the sides of the vehicle and carrying small
wheels to prevent friction. We now have a kind of rail which conforms
to the condition already mentioned, namely, that of being capable of
being laid down in front of the wheel of the truck or vehicle, and of
being picked up again when the weight has passed over any particular
part. The hoop, in fact, constitutes a rolling railway, and the larger
it can with convenience be made, the nearer is the approach which it
presents to a straight railway track as regards the absence of
resistance to the passing of a loaded truck-wheel over it.
The method of applying the rolling hoop, more particularly as regards
the question whether two or four shall be used for a vehicle, will
depend upon the special work to be performed. Some vehicles, however,
will have only two hoops, one on each side, but several small
truck-wheels running on the inside of each. A vehicle of this pattern
is not to be classed with a two-wheeled buggy, because it will
maintain its equilibrium without being held in position by shafts or
other similar means. So far as contact with the road is concerned it
is two-wheeled; and yet, in its relation to the force of gravitation
upon which its statical stability depends, it is a four or six-wheeler
according to the number of the small truck-wheels with which it is
fitted.
Traction engines carrying hoops twenty feet in height, or at any rate
as high as may be found compatible with stability when referred to the
available width on the road, will be capable of transporting goods at
a cost much below that of horse traction. The limit of available
height may be increased by the bringing of the two hoops closer to
each other at the top than they are at the roadway, because the
application of the principle does not demand that the hoops should
stand absolutely erect.
Similar means will, no doubt, be tried for the achievement of a
modified form of what has been dreamt of by cyclists under the name of
a unicycle. This machine will resemble a bicycle running on the inner
rim of a hoop, and will probably attain to a higher speed for show
purposes than the safety high-geared bicycle of the usual pattern. But
it is in the development of goods traffic along ordinary roads that
the hoop-rail principle will make its most noticeable progress. By its
agency not only will the transport of goods along well-made roads
become less costly and more expeditious, but localities in sparsely
settled countries--such as those beyond the Missouri in America and
the interior regions of South Africa, Australia and China--will become
much more readily accessible.
A traction-engine and automobile which can run across broad, almost
trackless plains at the rate of fifteen miles an hour will bring
within quick reach of civilisation many localities in which at
present, for lack of such communication, rough men are apt to grow
into semi-savages, while those who retain the instincts of
civilisation look upon their exile as a living death. It will do more
to enlighten the dark places of the earth than any other mechanical
agency of the twentieth century.