Krauss. Wilkinson. Rowan.
Diameter of cylinder.........d 5.5 in. 6.5 in. 5.1 in.
Length of stroke.............l 11.8 in. 9 in. 9.8 in.
Diameter of wheels...........D 31.5 in. 27.5 in. 29.5 in.
Pressure at which
boiler is worked...........P 220 lb. 147 lb. 191 lb.
(p(d^{2})l)/(2D).............E 1,210 lb. 1,509 lb. 805 lb.
Total heating surface........S 105 sq. ft. 105 sq. ft. 64 sq. ft.
Grate surface................G 2.7 sq. ft. 5.4 sq. ft. 3.1 sq. ft.
Surface of condenser.........C 274.482 s. ft. None. 861.120 s. ft.
Weight in running order
(motor only)...............P' 15,400 lb. 15,400 lb. 9,020 lb.
Weight in running order
(total)....................P" - - 15,400 lb.
Contents of water tank.......- 28.24 cub. ft. 13 cub. ft. 4.2 cub. ft.
Contents of coal bunks.......- 14.12 cub. ft. 12.5 cub. ft. 8.5 cub. ft.
P'/E 12.7 lb. 10.2 lb. 11.2 lb.
P"/E - - 19.125 lb.
P'/S 146 147 140
P'/G 5,722 2,855 2,889
C/S 2.6 - 13.4
C/G 102 - 275
The air, after being forced through the first pump cylinder, passed
successively through the other three, the diameters of which were of
proportionately decreasing sizes, viz., 8.2 in., 5 in., 3.5 in., and 2
in., and the air on leaving each cylinder passed on its way to the next
cylinder through a coiled pipe immersed in flowing water to remove the
heat generated. This cooling surface amounted to nearly 54 sq. ft.
The cooling of the air was very efficient. In an experiment made on this
question, the temperature of the compressor did not vary to the extent of
9° F. in charging the reservoir from 40 to 63 atmospheres, occupying an
hour and a half, the consumption of water during the time being about
1,400 gallons.
The fixed reservoirs were of about 240 cubic feet capacity.
The motor formed part of a compound vehicle, which may be said to have
consisted of two parts joined together by an articulated corridor, the
whole being covered by a roof which was approached from the platform
behind by an easy staircase. On this roof were seats for outside
passengers.
The front part of the compound vehicle contained the motor, as well as a
compartment for six inside passengers, with roof space for twenty
passengers, and weighed about 15,400 lb. when empty; the hind part
contained accommodation inside for twelve passengers, and outside for
fourteen passengers, and weighed 6,600 lb.
The combined vehicle was entered from the platform in the rear, which
could hold four passengers, and from thence, as already mentioned, the
staircase led on to the roof. The total number of passengers this vehicle
could accommodate was thus eighteen inside, thirty-four on the roof, four
on the platform, or fifty-six in all.
The total length of the carriage was 29 ft. 7 in., the width 7 ft. The
distance between the axes of the bogies was 16 ft. 9 in. The distances
apart of the centers of the wheels were in the case of the hind bogie 3
ft. 9 in., and in the case of the front bogie 4 ft. 4.6 in.
The motor is a compound engine, the diameters of the cylinders being 4.9
in. and 1.9 in., with a 12 in. stroke. The diameter of the wheels was 2
ft. 4 in. A small boiler is placed on one side, in front, for creating
steam, which passes into a steam-jacket, inclosing the pipe of
communication from the reservoir to the cylinders, as well as the
cylinders themselves, so that the air was warmed before it escaped. The
reservoirs on the motor contained 71 cubic feet.
In an experiment made on charging the reservoir in the motor, the
pressure in the fixed reservoirs, at the time of charging the reservoirs
on the motor, was 63.8 atmospheres, at a temperature of 68° F. One
atmosphere was lost by letting the air into the pipe laid between the
shed and the tramway where the motor stood; when the reservoir on the
motor was charged, the pressure fell to 42.6 atmospheres in the fixed
reservoirs, at a temperature of 55° F.
The pressure in the reservoir on the motor, when ready to start, was 42.6
atmospheres, at a temperature of 84° F. On its return, at the end of
forty-six minutes, after a journey as above mentioned of about three and
a quarter miles including the triangle, the pressure had fallen to 20.9
atmospheres, and the temperature to 71° F. The weight of air used during
the journey was thus about 110 lb., or, say, 34 lb. per mile. The coal
consumed by the stationary engine to compress the air amounted to 39 lb.
per mile, in addition to 3 lb. of coke per mile for warming the exhaust.
While the motor was performing its journey, the stationary steam-engine
was employed in raising the pressure in the fixed cylinders to 63
atmospheres, and worked, on an average, during fifty minutes in each
hour; during the rest of the journey it remained idle. It was thus always
employed in doing work in excess of the pressure which could be utilized
on the car, and the work was, under the circumstances of the case,
necessarily intermittent. This was a very unfavorable condition of
working.
In the electric tram-car the haulage was effected by means of
accumulators. The car was of the ordinary type with two platforms. It was
said to have been running as an ordinary tram-car since 1876. It had been
altered in 1884 by raising the body about six inches, so as to lift it
clear of the wheels, in order to allow the space under the seats to be
available for receiving the accumulators, which consisted of Faure
batteries of a modified construction. The accumulators employed were of
an improved kind, devised by M. Julien, the under manager of the
Compagnie l'Electrique, which undertook the work.
The principal modification consists in the substitution, for the lead
core of the plates, of one composed of a new unalterable metal. By this
change the resistance is considerably diminished, the electromotive force
rises to 2.40 volts, the return is greater, the output more constant, and
the weight is considerably reduced. The plates being no longer subject to
deformation have the prospect of lasting indefinitely. The accumulators
used were constructed in August, 1884.
The car, as altered, had been running as an electric tram-car on the
Brussels tramways since October, 1884, till it was transferred to the
experimental tramway at Antwerp. The accumulators had been in use upon
the car during the whole of this period, and they were in good order at
the end of the experiments, that is to say, when the exhibition closed at
the end of October, 1885.
The accumulator had forty elements, divided into four series, each series
communicating, by means of wires fixed to the floor of the car, with
commutators which connected them with the dynamo used as a motor.
There were two sets of these batteries or accumulators, one of which was
being charged in the shed while the other was in use. The exchange
required ten minutes, including the time for the car to go off the
tramway into the shed and return to the tramway. This exchange took place
after every seven journeys. Therefore, the two batteries would have
sufficed for working the car over a distance of about forty-two miles
during sixteen hours.
It may be observed that the first service in the morning would be
performed by means of the accumulators charged during the afternoon and
evening of the previous day.
Each element of a battery was composed of nineteen plates, of which nine
were positive, four millimeters thick, and ten negative, three
millimeters thick. Each positive plate weighed 1.44 lb., of which about
twenty-five per cent. consisted of active material. Each negative plate
weighed nearly 1 lb., of which one-third consisted of active matter. The
weight of the metallic part of the battery amounted, therefore, to 1,846
lb.; and the whole battery, including the case and the liquid, amounted
to 2,464 lb., which contained 499 lb. of active matter, or about 20.25
per cent. The four cases in which the battery was contained were so
arranged as to divide the weight equally between the wheels.
Two commutators inclosed in a box were placed on the platforms at the two
ends of the carriage, so as to be available for moving in either
direction.
The accumulators were divided into four series of ten double elements,
which, by means of the commutators, could be united under four
combinations, viz.:
1st. 4 series in quantity--1 in tension.
2d. 2 " " " 2 "
3d. 3 "
4th. 4 "
Finally, a fifth movement united the four series in quantity, coupling
them on each other, and putting the dynamo out of circuit, thus restoring
equilibrium. When in a state of repose, the handle was so arranged as to
keep this latter switch turned on. The accumulators were arranged for
charging in two series united in quantity, each containing twenty double
elements. The charge was effected by a Gramme machine, worked by a
portable engine. Each of these series received its charge during seven
hours for the ordinary service of the car, and during nine hours for the
accelerated service.
The accumulators on the car actuated a Siemens dynamo, acting as a motor,
such as is used for lighting, having a normal speed of 1,000 revolutions,
fixed on the frame of the carriage. The motion was conveyed from the
pulley on the dynamo by means of a belt passing round a shaft fixed on
movable bearings to regulate its tension, and thence to the axles by
means of a flat chain of phosphor bronze. The chain was adopted as the
means of moving the axle, on account of its simplicity and facility of
repair by unskilled labor.
The speed was fixed at 4 meters per second (which corresponds with a
speed of nearly 9 miles per hour) for 1,000 revolutions of the dynamo;
and it was regulated by cutting a certain number of the accumulators out
of circuit, instead of by the device of inserting resistances, which
cause a waste of energy. By breaking the circuit entirely the motive
power ceased, and the vehicle might either be stopped by the brakes or
allowed to run forward by gravity, if the road were sufficiently
inclined. The reversal of the motor was effected by means of a lever
which reversed the position of the brushes of the dynamo.
The dynamo could be set in motion, and the carriage worked from either
end, as desired. The handle to effect this was movable, and as there was
only one handle, and this one was in charge of the conductor, he used it
at either end as required.
It should be mentioned that the car was lighted at night by two
incandescent lamps, which absorbed 1.5 amperes each; and the brakes also
were worked by the accumulators.
The weight of the tram-car was 5,654 lb.; the weight of the accumulators
was 2,460 lb.; the weight of the machinery, including dynamo, 1,232 lb.
The car contained room for fourteen persons inside and twenty outside.
Under the conditions of the competition the car was required to draw a
second car occasionally.
The jury made special observations upon the work required to move the car
between the 20th September and 15th October, 1885. Seals were attached to
the accumulators. Moreover, from the 27th of September, after each
charge, seals were placed on the belts from the steam-engine to prevent
any movement of the Gramme machine, so that there could be no charges put
into the accumulators beyond those measured by the jury.
The instruments used for measuring were Ayrton's amperemeter and Deprez's
voltmeter, which had been tested in the exhibition by the Commission for
Experiments on Electrical Instruments, under the presidency of Professor
Rousseau. Besides this, Siemens' electro-dynamometer and Ayrton's
voltmeter were used to check the results; but there was no practical
difference discovered. During the period of charging the accumulators,
the intensity of the current and the electromotive force was measured
every quarter of an hour, and thence the energy stored up in the battery
was deduced. It may be mentioned that the charge in the accumulators,
when the experiments were commenced, was equal in amount to that at their
termination.
An experiment was made on 21st October to ascertain, as a practical
question, what was the work absorbed by the Gramme machine in charging
the accumulators. The work transmitted from the steam-engine was measured
every quarter of an hour by a Siemens dynamometer; at the same time the
intensity of the electromotive force given out by the machine, as well as
the number of the revolutions it was making, was noted. It resulted that
for a mean development of 4 mechanical horse power, the dynamometer gave
into the accumulators to be stored up 2.28 electrical horse power, or 57
per cent. The intensity varied between 25.03 and 23.51 amperes during the
whole time of charging. Of this amount stored up in the accumulators a
further loss took place in working the motor; so that from 30 to 40 per
cent. of the work originally given out by the steam-engine must be taken
as the utmost useful effect on the rail.
It was estimated that to draw the carriage on the level 0.714 horse power
was required, or if a second carriage was attached, 0.848 horse power
would draw the two together. This would mean that, say, 2 horse power on
the fixed engine would be employed to create the electricity for
producing the energy required to draw the carriage on the level.
The electric tram-car was quite equal in speed to those driven by steam
or compressed air, and was characterized by its noiselessness and by the
care with which it was manipulated.
Assuming the car, by itself, cost the same as an ordinary tram-car, the
extra cost relatively to other systems was stated as being according to
the following figures, viz.: the Gramme machine cost £48, the motor £208,
and the accumulators 2.25 francs per kilogramme (10d. per pound). To
these must be added the cost of erection, and of switches for
manipulating the current; as well as the proportion of the cost of a
fixed engine to create the electricity.
Having thus given a general description of the various motors which were
presented for competition, I will now give a brief summary of some of the
principal particulars obtained during the competition. In the first
place, it may be mentioned that the jury consisted of the following:
President.--M. Hubert, Ingénieur en Chef, Inspecteur de Direction à
l'administration des chemins de fer de l'Etat Belge.
Vice-President.--M. Beliard, Ingénieur des Arts et Manufactures, délégué
par le Gouvernenent Français.
Members.--MM. Douglas Galton, Capitaine du Génie, délégué par le
Gouvernement Anglais; Gunther, Ingénieur, Commissaire Général de la
Section allemande à l'Exposition d'Anvers; Huberti, Ingénieur à
l'administration des chemins de fer de l'Etat Belge, Professeur à
l'Université de Bruxelles; Dery, Ingénieur Chef de service à
l'administration des chemins de fer de l'Etat Belge.
Secretary.--M. Dupuich, Ingénieur Chef du service du matérial et de la
traction à la Société Générale des chemins de fer économiques.
Reporter.--M. Belleroche, Ingénieur en Chef, à la traction et au matérial
des chemins de fer du Grand Central.
Members added by the Jury.--MM. Vincotte, Ingénieur, Directeur de
l'Association pour la surveillance des machines à vapeur; Laurent,
Ingénieur des mines et de l'Institut électro-technique de l'Université de
Liége.
The original programme of the conditions which were laid down in the
invitation to competitors, as those upon which the adjudication of merit
would be awarded, contained twenty heads, to each of which a certain
value was to be attached; and, in addition to these special heads, there
were also to be weighed the following general considerations, viz.:
a. The defects or inconveniences established in the course of the trials.
b. The necessity or otherwise of turning the motor, or the carriage with
motor, at the termini.
c. Whether one or two men would be required for the management of the
engine.
As regards these preliminary special points, the compressed air motor, as
well as the Rowan engine, required to be turned for the return journey,
whereas the other motors could run in either direction.
In regard to this, the electric car was peculiarly manageable, as it
moved in either direction, and the handle by which it was managed was
always in front, close to the brake. This carriage was the only one which
was entirely free from the necessity of attending to the fire during the
progress of the journey, for even the compressed air engine had its small
furnace and boiler for heating the air.
Each of the motors under trial was managed by one man.
The several conditions of the programme may be conveniently classified in
three groups, under the letters A, B, C. Under the letter A have been
classed accessory considerations, such as those of safety and of police.
These are of special importance in towns. But their relative importance
varies somewhat with the habits of the people as well as with the
requirements of the authorities; for instance, in one locality or country
conditions are not objected to which, in another locality, are considered
entirely prohibitory.
The conditions under this head are:
1. Absence of steam.
2. Absence of smoke and cinders.
3. Absence, more or less complete, of noise.
4. Elegance of aspect.
5. The facility with which the motor can be separated
from the carriage itself.
6. Capacity of the brake for acting upon the greatest
possible number of wheels of the vehicle or vehicles.
7. The degree to which the outside covering of the
motor conceals the machinery from the public, while
allowing it to be visible and accessible in all parts to
the engineer.
8. Facility of communication between the engineer
and the conductor of the train.
In deciding upon the relative merits of the several motors, so far as the
eight points included under this heading are concerned, it is clear that,
except possibly as regards absence of noise, the electrical car surpassed
all the others.
The compressed air car followed, in its superiority in respect of the
first three points, viz., absence of steam, absence of smoke, and
absence of noise; but the Rowan was considered superior in respect of the
other points included in this class.
Under the letter B have been classed considerations of maintenance and
construction.
9. Protection, more or less complete, of the machinery against the
action of dust and mud.
10. Regularity and smoothness of motion.
11. Capacity for passing over curves of small radius.
12. The simplest and most rational construction.
13. Facility for inspecting and cleaning the interior of the boilers.
14. Dead weight of the train compared with the number of places.
15. Effective power of traction when the carriages are completely full.
16. Rapidity with which the motor can be taken out of the shed and
made ready for running.
17. The longest daily service without stops other than those
compatible with the requirements of the service.
18. Cost of maintenance per kilometer. (It was assumed, for the
purposes of this sub-heading, that the motor or carriage which
gave the best results under the conditions relating to
paragraphs 9, 10, 12, and 13 would be least costly for repairs.)
As regards the first of these, viz., protection of the machinery against
dirt, the machinery of the electrical car had no protection. It was not
found in the experiments at Antwerp that inconvenience resulted from
this; but it is a question whether in very dusty localities, and
especially in a locality where there is metallic dust, the absence of
protection might not entail serious difficulties, and even cause the
destruction of parts of the machinery.
In respect to the smoothness of motion and facility of passing curves,
the cars did not present vary material differences, except that the cars
in which the motor formed part of the car had the preference.
In the case of simplicity of construction, it is evident that the
simplest and most rational construction is that of a car which depends on
itself for its movement, which can move in either direction with equal
facility, which can be applied to any existing tramway without expense
for altering the road, and the use of which will not throw out of
employment vehicles already used on the lines; the electric car fulfilled
this condition best, as also the condition numbered 13, as it possessed
no boiler.
In respect to No. 14, viz., the ratio of the dead weight of the train to
passengers, if we assume 154 lb. as the average weight per passenger, the
following is the result in respect of the three cars in which the power
formed part of the car:
9,350 lb.
Electric car. --------- = 1.78
154 × 34
15,950 lb.
Rowan. ---------- = 2.30
154 × 45
22,000 lb.
Compressed air. ---------- = 2.55
154 × 56
The detached engines gave, of course, less favorable results under this
head.
Under head No. 15 the tractive power of all the motors was sufficient
during the trials, but the line was practically level, therefore this
question could only be resolved theoretically, so far as these trials
were concerned, and the table before given affords all the necessary data
for the theoretical calculation.
As regards the rapidity with which the motors could be brought into use
from standing empty in the shed, the electric car could receive its
accumulators more rapidly than could the boiler for heating the exhaust
of the compressed-air car be brought into use.
As regards the steam motors, the following were the results from the time
of lighting the fires:
The Rowan--
In 34 minutes 3 atmospheres.
" 36 " 4 "