MOTOR POWER AND ITS TRANSMISSION
It is unnecessary to describe the methods by which power for mining
purposes has been obtained--that is, up to within the last five
years--beyond a general statement, that when water power has been
available in the immediate locality of the mine, this cheap natural
source of power has been called upon to do duty. Steam has been the
alternative agent of power production applied in many different ways,
but labouring under as many disadvantages, chief of which are lack of
water, scarcity of fuel and cost of transit of machinery. Sometimes
condensing steam-engines have been employed. For the generation of steam
the semi-portable and semi-tubular have been the type of boiler that has
most usually been brought into service. Needless to say, when highly
mineralised mine water only is available the adoption of this class of
boiler is attended with anything but satisfactory results.
Recently, however, there is strong evidence that where steam is the
power agent to be employed the water-tube type of boiler is likely to be
employed, and to the exclusion of all other forms of apparatus for the
generation of steam. The advantages of this type, particularly the
tubulous form (or a small water tube), made as it is in sections, offers
unrivalled facilities for transport service. The heaviest parts need not
exceed 3 cwt. in weight, and require neither heavy nor yet expensive
brickwork foundations.
WATERLESS POWER.
The difficulties in finding water to drive a steam plant are often of
such a serious character as to involve the abandonment of many payable
mines; therefore, a motive power that does not require the aqueous agent
will be a welcome boon.
It will be a source of gratification to many a gold-claim holder to
know that practical science has enabled motive power to be produced
without the necessity of water, except a certain very small quantity,
which once supplied will not require to be renewed, unless to compensate
for the loss due to atmospheric evaporation.
Any carbonaceous fuel, such as, say, lignite, coal, or charcoal, can be
employed. The latter can be easily produced by the method described in
the Chapter on “Rules of Thumb,” or by building a kiln by piling
together a number of trunks of trees, or fairly large-sized branches,
cut so that they can be built up in a compact form. The pile, after
being covered with earth, is then lighted from the base, and if there
are no inlets for the air except the limited proportion required for the
smouldering fire at the base, the whole of the timber will be gradually
carbonised to charcoal of good quality, which is available for the
waterless power plant.
The waterless power plant consists of two divisions: First, a gas
generating plant; secondly, an internal combustion or gas engine in
which the gas is burnt, producing by thermo-dynamic action the motive
power required. The system known as the Thwaite Power Gas System is not
only practically independent of the use of water, but its efficiency in
converting fuel heat into work is so high that no existing steam plant
will be able to compete with it.
The weight of raw timber, afterwards to be converted into charcoal, that
will be required to produce an effective horse-power for one hour equals
7 lb.
If coal is the fuel 1⅓ lb. per E. H. P. for one hour’s run.
If lignite ” 2½ ” ” ”
The plant is simple to work, and as no steam boiler is required the
danger of explosions is removed. No expensive chimney is necessary for
the waterless power plant.
Where petroleum oil can be cheaply obtained, say for twopence per
gallon, one of the Otto Cycle Oil Engines, for powers up to 20 indicated
horse-power, can be advantageously employed.
These engines have the advantage of being a self-contained power,
requiring neither chimney nor steam boiler, and may be said to be a
waterless power. The objection is the necessity to rely upon oil as
fuel, and the dangers attending the storage of oil. A good oil engine
should not require to use more than a pint of refined petroleum per
indicated horse-power working for one hour.
Fortunately for the mining industry electricity, that magic and
mysterious agency, has come to its assistance, in permitting motive
power to be transmitted over distances of even as much as 100 miles with
comparatively little loss of the original power energy.
Given, that on a coal or lignite field, or at a waterfall, 100
horse-power is developed by the combustion of fuel or by the fall of
water driving a turbine, this power can be electrically transmitted to a
mine or GROUP OF MINES, say 100 miles away, with only a loss of some 30
horse-power. For twenty miles the loss on transmission should not exceed
15 horse-power, so that 70 and 85 horse-power respectively are available
at the mines. No other system offers such remarkable efficiencies of
power transmission. The new Multiphase Alternating Electric Generating
and Power Transmission System is indeed so perfect as to leave
practically no margin for improvement.
The multiphase electric motor can be directly applied to the stamp
battery and ore-breaker driving-shaft and to the shaft of the
amalgamating pans.
Approximate Power Required to Drive the Machinery of a Mine.
Rock breaker 10 effective horse-power
Amalgamating pan 5 ” ”
Grinding pan 6 ” ”
Single stamp of 750 lb. dropping
90 times per minute 1·25 ” ”
Settlers 4 ” ”
Ordinary hoisting lift 20 ” ”
Allow 10 per cent. in addition for overcoming friction.
Besides this electrical distributing power, which should not cost more
than three farthings per effective horse-power per hour, the electrical
energy can be employed for lighting the drives and the shafts of the
mine. The modern electrical mine lamps leave little to be desired. Also
it is anticipated that once the few existing difficulties have been
surmounted electric drilling will supplant all other methods.
Electric power can be employed for pumping, for shot firing, for
hauling, and for innumerable purposes in a mine.
Electricity lends itself most advantageously to so many and varied
processes, even in accelerating the influence of cyanide solutions on
gold, and in effecting the magnetic influence on metallic particles in
separating processes; while applied to haulage purposes, either on
aërial lines (Fig. 26) or on tram or railroads, it is an immediate and
striking success.
[Illustration: FIG. 26. ELECTRICAL AËRIAL TRAMWAY.]
It is anticipated that in the near future the mines on the Rand, South
Africa, will be electrically driven from a coalfield generating station
located on the coalfields some thirty miles from Johannesburg. Such a
plant made up of small multiples of highly efficient machines will
enable mine-owners to obtain a reliable power to any extent at immediate
command and at a reasonable charge in proportion to the power used. This
wholesale supply of power will be a godsend to a new field, enabling the
opening up to be greatly expedited; and no climatic difficulties, such
as dry seasons, or floods, need interfere with the regular running of
the machinery. The same system of power-generation at a central station
is to be applied to supply power to the mines of Western Australia.