RESULTS OF EXPERIMENTS ON MECHANICAL MOTORS FOR TRAMWAYS MADE BY THE
JURY ON RAILWAY APPLIANCES AT THE ANTWERP EXHIBITION.
By Captain DOUGLAS GALTON, D.C.L., O.B., F.R.S.
An interesting feature of the International Exhibition at Antwerp was the
competition which was invited between different forms of mechanical
motors on tramways for use in towns, and between different forms of
engines for use on light railways in country districts, or as these are
termed, "Chemins de Fer Vicinaux."
These latter have obtained a considerable development in Belgium, Italy,
and other Continental states; and are found to be most valuable as a
means of cheapening the cost of transit in thinly peopled districts. But
owing to the fact that the Board of Trade regulations in this country
have not recognized a different standard of construction for this class
of railway from that adopted on main lines, there has been no opportunity
for the construction of such lines in England.
There has, however, been a great development of tramway lines in England,
which in populous districts supply a want which railways never could
fully respond to; and although hitherto mechanical traction has not
attained any very considerable extension, it is quite evident that if
tramways are to fullfil their object satisfactorily, it must be by means
of mechanical traction.
It is also certain that the mechanical motor which shall be found to be
most universally adaptable, that is to say, most pliant in accommodating
itself to the various lines and to the varying work of the traffic, will
be the form of motor which will eventually carry the day.
The competition between different forms of motors at the Antwerp
Exhibition, which was carefully superintended, and which was arranged to
be carried on for a reasonable time, so as to enable the qualities and
defects of the different motors to be ascertained, affords a starting
point from which it will be possible to carry on future investigations.
I have, therefore, thought it advantageous to the interests of the
community in this country to bring the results arrived at before this
Society; and as the "Chemins de Fer Vicinaux," to which one part of the
competition was devoted, have no counterpart in this country, it is
proposed to limit the present paper to an account of the experiments made
on the motors for tramways.
Certain conditions were laid down in the programme published at the
opening of the Exhibition, to regulate the competition, in order that the
competitors might understand the points which would be taken into account
by the judges in awarding the prizes.
The experiments were made upon a line of tramway laid down for the
purpose in the city of Antwerp, carried along the boulevards from near
the main entrance of the exhibition to the vicinity of the principal
railway station, a distance of 2,292 meters.
The line ended in a triangle of 505 meters, in order that those motors
which required to run always in the same direction should be enabled to
do so.
Out of the whole length of the line, viz., 2,797 meters, 2,295 meters
were in a straight line, 189 meters in curves of 1¾ chains radius, and
313 meters in curves of 1 chain radius. There were on the line four
passing places, besides a passing place at the terminus; these were
joined to the main line by curves of 1¾ chains radius.
The line was practically level, the steepest incline being 1 in 1,000;
this circumstance is somewhat to be regretted, but the city of Antwerp
afforded no convenient locality where a line with steep gradients could
have been obtained. The motors were kept in sheds close to the
commencement of the line of tramway near the exhibition, where all
necessary cleaning and such minor repairs as were required could take
place.
A regular service was established, according to a fixed time-table, to
which each motor was required to conform. Each journey was reckoned as
starting from the end near the exhibition, proceeding to the beginning of
the triangle, and returning to the starting point. An hour was allowed
between the commencement of each journey, fourteen minutes were allowed
for a stoppage at the end near the exhibition, and eighteen minutes at
the other end--thus allowing twenty-eight minutes for traveling 2 miles
1,500 yards, or a traveling speed of about 6 miles an hour. The motors
were required to work four days out of six, and on one of the four days
to draw a supplementary carriage.
An official, assisted by a storekeeper, was appointed to keep a detailed
record--
1. Of the work done by each of the motors.
2. Of any delays occurring on the journey, and of the
causes of delay.
3. Of the consumption of fuel, both for lighting the
fires and for working.
4. Of the consumption of grease.
5. Of the consumption of water.
6. Of all repairs of whatever nature.
7. Of the frequency of cleaning and other necessary
operations required for the efficient service of the
motor.
The experiments lasted about four months. Five competitors offered
themselves, which may be classed as follows: Three were propelled by the
direct action of steam, and two were propelled by stored-up force
supplied from fixed engines.
_Propelled by the direct action of the steam._
1. The Krauss locomotive engine, separate from the carriage.
2. The Wilkinson locomotive engine (i.e., Black and
Hawthorn), also separate from the carriage.
3. The Rowan engine and carriage combined.
_Propelled by stored-up force._
4. The Beaumont compressed-air engine.
5. The electric carriage.
It is somewhat to be regretted in the public interest that other forms of
mechanical motors, such as the Mekarski compressed-air engine, or the
engine worked with superheated water, or cable tramways, or electrical
tramways, were not also presented for competition.
1. The Krauss locomotive is of the general type of a tramway locomotive,
but with certain specialties of construction. It has coupled wheels. The
weight is suspended on three points. The water-tanks form part of the
framing on each side; a covering conceals all except the dome of the
boiler. Above the roof is a surface condenser, consisting of 108 copper
tubes placed transversely, each of which has an external diameter of 1.45
inches. The boiler is similar to that of an ordinary locomotive; its axis
is 3 feet 10½ inches above the road. The body of the engine is 9 feet 11
inches long, and 7 feet 2½ inches wide. The axles are 4 feet 11 inches
from center to center. The platform extends along each side of the
boiler; the door of the fire-box is in the axis of the road. The engine
driver stands on the right-hand side, in the middle of the motor, where
he has command of all the appliances for regulating the movements of the
engine as well as of the brake.
The Wilkinson (Black and Hawthorn) engine had a vertical boiler and
machinery. The cylinders were on the opposite side of the boiler from the
door of the fire box, and mounted independently; the motion of the piston
was communicated by means of a crank shaft and toothed wheels to the
driving axle. The wheels were coupled. A regulator, injector, and a
hand-brake were placed at each end, so that the engine driver could
always stand in the front, whichever was the direction in which the
engine moved; and there was a platform of communication between the two
ends, carried along one side of the boiler.
The boiler was constructed with "Field" tubes, the horizontal tube plate
having a flue in the middle which carried the heated gases into the
chimney.
The visible escape of the steam is prevented by superheating. To effect
this, the steam, as it leaves the cylinder, passes into a cast iron
chamber adjacent to the boiler, which is intended to retain the water
carried off with the steam. From thence the steam passes into a second
chamber, suspended at a small height above the grate in the axis of the
boiler and of the flue which conveys the heated gases into the chimney,
and thence into a sort of pocket inclosed in the last-mentioned chamber,
which is open at the bottom, and the upper part of which terminates in a
tube passing into the open air. This method of dissipating the steam
avoids the necessity of a condenser; but if it be admitted that the steam
in escaping has a minimum temperature of 572° Fahr., it will carry away
12 per cent. more caloric than would have been required to raise it to a
pressure of 150 lb. per square inch.
The steam escaping through the safety valve is passed through the same
apparatus.
The toothed wheel on the driving axle is arranged to act upon another
toothed wheel on a shaft connected with the regulator, so as to control
its speed automatically.
The length of the engine is 10 ft. 10 in., its width 5 ft. 9 in., and the
distance from center to center of the wheels 5 ft. 2 in.
The Rowan tram-car consists of a body 31 feet long and 7 feet wide,
resting on a two-wheeled bogie behind and on a four-wheeled bogie in
front, this front bogie being the motor, and the whole has the appearance
of a long railway carriage, somewhat in the form of an omnibus with a
platform at each end, of which the front platform is occupied by the
engine. It requires, therefore, either a turntable or a triangle at the
end of the line, so as to enable it to reverse its direction.
This motor is a steam engine of light and simple form, supplied with
steam from a water tube boiler with very perfect combustion, so that no
smoke escapes. The boiler is somewhat on the principle of a Shand and
Mason boiler; it is so built that It can easily be opened and every part
of the interior examined and cleaned.
The peculiarity of the Rowan motor is the simplicity of the attachment of
the engine to the carriage, and the facility with which it can be
detached when required for cleaning or repair, viz., in five or six
minutes.
The steam can be got up in the engine with great rapidity if a change of
engine is required. When, however, the engine is detached, the carriage
loses its support in front, and is therefore not serviceable. When
necessary, the combined motor can draw a second ordinary carriage.
The motor by itself occupies a length of 9 ft. 8 in. It has two
horizontal cylinders; the four wheels of the bogie are coupled, and
between the wheels the sides of the framing are rounded to allow two
vertical boilers to stand. These boilers have vertical tubes for the
water, which are joined together at the top by a horizontal cylinder.
Each boiler, with its covering, is 1 ft. 9 in. in diameter. The boilers
stand 1 ft. 9 in. apart, thus affording space between them for the motive
machinery, including the pump. The crank axle is behind the boilers. The
levers, the injector, the access to the fire-box, a pedal for working the
engine brake as well as a screw brake for the carriage, are all in front.
The brakes act on all six wheels, are worked by the driver, and the whole
weight of the engine, car, and passengers being carried on these wheels,
the car can be stopped almost instantaneously; and as over two-thirds of
the entire weight of the car and passengers rests on the four driving
wheels; there is always sufficient adhesion on all reasonable inclines,
and the adhesion is augmented as the number of passengers carried
increases. Hence this car is adapted for lines with heavy grades.
A small water tank is attached to the framing; two small boxes for coal
or coke, with a cubic capacity of about 3½ feet, are attached to the
plate in front of the bogie. The covering of the boilers is in two parts,
which are put on from each side horizontally, and screwed together in the
center. The removal of the upper part enables the tubes to be examined
and cleaned. The draught is natural; the base of the chimney is 3 ft. 2
in, from the grate; the height of the chimney is 5 ft. 2 in.
The steam from the cylinders passes directly into a condenser placed on
the top of the carriage. The condenser is made of corrigated copper
sheets millimeter thick. Two sheets, about 15 to 18 inches wide and 15
feet long, are laid together and firmly soldered, forming a chamber.
Twenty of these chambers are placed side by side on the top of the
carriage, connected with a tube at each end, so as to allow the steam to
pass freely through them. The lower corrugations in the several chambers
are connected together, and thence a pipe with a siphon to stop the steam
is carried to a water tank under the carriage, which thus receives the
condensed water. This arrangement afforded a condensing surface of about
800 square feet. It should be mentioned that with larger engines Mr.
Rowan employs as much as 1,600 feet of condensing surface. The nearness
of the chambers to each other tends no doubt to diminish the power of
condensing the steam, but this is somewhat compensated by the artificial
circulation of air produced by the movement of the carriage. But in any
case, if there is surplus steam, the pipe from the condenser causes it to
pass under the grate, whence it rises superheated and invisible through
the fire and up the chimney.
Under the carriage attached to the framing are four reservoirs, holding
about three and a half cubic feet of water, of which water space one-half
acts as a reservoir for cold feed water, and half for the condensed
water. A tube from the small reservoir on the engine communicates through
valves with the reservoirs of hot and cold water on the carriage.
The consumption of cold water measured during two days was 2.86 lb. per
kilometer; assuming that the boiler evaporated 6.5 lb. of water per pound
of coal, the cold water formed one-fifth of the total feed water
required.
The carriage, i. e., the part occupied by passengers, is 21 ft. 8 in. in
length. It holds seats for forty-five passengers, besides those who would
stand on the gangway and platform. The seats are placed transversely on
each side of a central corridor, each seat holding two people. The
platform of the carriage is about 2 ft. 6 in. above the rails. Passengers
have access to the interior from behind by means of the end platform, and
in front near the engine from the two sides. As already mentioned, the
hind part of the carriage rests upon two wheels, the front part being, as
already mentioned, supported on the engine bogie. To effect this support,
the hinder part of the framing of the engine is formed in a half circle,
with a broad groove, in which the ends of two springs are arranged to
slide. The centers of the springs form the support of the framing of the
carriage.
The framing of the engine bogie is attached to the hind bogie truck of
the carriage by two diagonal drawbars. The coupling is effected by bolts
close to the engine, and the car is drawn entirely by means of the bogie
pin of the hind bogie. The trucks are 16.5 ft. apart.
Table I. above shows the dimensions of different parts of these three
steam motors, as well as their weights.
The Beaumont engine, worked by compressed air, may be generally said to
be similar to that described in a paper read before the Society of Arts
on the 16th March, 1881, to which, however, some improvements have been
since introduced.
The apparatus for compressing the air was placed in the shed. The air was
compressed to 63 atmospheres by a pump worked by a steam engine, and
stored in cylindrical reservoirs of wrought iron without rivets. A pipe
led the air from the reservoirs to the head of the tramway, where the
cylinder placed on the motor for storing the air during the journey could
be conveniently charged.
The air was compressed by means of four pumps, placed two and two in a
water-box, and worked by the direct action of a compound engine, with
cylinders, placed in juxtaposition, of 8 in. and 14 in. diameter
respectively, with an equal length of stroke of 13 in.