A description of the mode of using water-power for driving the North
Bloomfield tunnel in California, some years since, will give a good
illustration of some of the advantages of the hurdy-gurdy. This tunnel was
originally about 8,000 feet long, through a slate highly metamorphosed,
with its general line passing under a good-sized stream, at a depth of
about 190 feet. There were eight working-shafts, each about 200 feet deep,
which, with the lower entrance or portal, gave sixteen working faces.
Diamond drills were used at the lower heading requiring power; the other
fifteen headings were driven by hand-work. It was uncertain how much water
would be encountered; but from the location, it was evident that a large
quantity might be struck in any shaft, and hence it became necessary to
have ample power at hand at each opening, in readiness for such an
emergency. A pipe main was laid along the general line of the tunnel, with
its pen-stock 285 feet vertical above the surface at the upper shaft, and
549 feet above the lowest shaft. It was made of single riveted sheet-iron,
of No. 14 (Birmingham) gauge, in lengths of 20 feet, put together
stove-pipe fashion, with the joints made tight by cloth tarred strips and
pine wedges. This pipe had a diameter of 15 inches at the pen-stock,
diminishing from this to 13, 11, and 7 inches at its lower end. From it,
short branches, 7 inches in diameter, were extended to the several shafts.
It was in one place carried across the stream by a light suspension
bridge, some 150 feet long, the trunk of a tree on each side forming a
convenient tower. The aggregate length of the main and branches was 9,960
feet, with some 2,500 feet additional, for the branch to the diamond
drills. The pipe was laid on the surface of the ground, its only
protection being in places a couple of 1½-inch planks tacked together, and
placed over it; the range of temperature was from 10 degrees to 107
degrees Fahr. (in the shade). It was inspected by the foreman of the
tunnel-work as he daily walked over the line; besides the occasional
driving of a few wedges and putting on a band or two, it gave no trouble
from leakage, which probably for its entire length did not amount to more
than an average of 3 or 4 cubic feet a minute; from time to time, a little
sawdust was put into the pen-stock. Three stop-gates were placed on the
main, and a separate stop-gate at each shaft, operated by a fine-threaded
screw, so that the water could be cut off when desired.
[Illustration: FIG. 13.]
Fig. 13 shows the arrangement of the machinery for hoisting and pumping,
which was identical at the several shafts, except that the hurdy-gurdies
varied from 16½ feet in diameter at the upper shaft to 21 feet at the
lowest shaft. The water-wheel moved only in one direction; the pinion on
the wheel-shaft drove the spur-wheel, to which the pitman of the pump-bob
was attached. On the spur-wheel shaft was a friction-gear, driving the
hoisting-reel; this reel was mounted on sliding blocks, so that hoisting
was done by putting it in gear, the empty load being dropped by a
friction-band. Changing the size of the water-wheel as the pressure
increased permitted the use of the same pattern of machinery at the
different shafts. The water was brought to the wheel by a discharge-pipe,
some nine feet long, having a vertical movement by ball-and-socket joint,
so that at pleasure, by dropping the pipe, the machinery could be run at
various speeds, or entirely stopped. At the end of this discharge-pipe
was a cast tapered nozzle, about 3½ inches in diameter, in which was
inserted a ring of saw-plate steel having the desired diameter, and which
was held in place by an annular screw-cap. By changing the ring, which
only required a few moments' time, any desired amount of water, up to 3 or
4 cubic feet a second, could be discharged against the wheel. The
stop-gate was left wide open while the machinery was running. The pumping
was done by eighteen pumps, of Cornish pattern; the largest amount of
water pumped from any one shaft was something over 30 cubic feet a minute;
the power at hand, however, was ample to pump more than twice that
quantity. It was rather curious at, this shaft to see more water coming
from the pumps than was used on the wheel. The two diamond drills were
driven by a small hurdy-gurdy set on the rear of the drill carriage. This,
but at another tunnel, was afterward modified by placing a separate
hurdy-gurdy on a sleeve on each drill-rod; the advance movement of the
drill being given by hydrostatic pressure on an annular piston, thus doing
away with all gearing. These eight sets of machinery were run for nearly
2½ years' time; the only break being that of a spur-wheel, doubtless
caused by the careless dropping of a steel bar between it and its pinion.
Aside from this accident, practically not a dollar was spent for repairs,
and the machinery, including the pipe, was in about as good order when the
tunnel was finished as when it was first erected. One man, on a twelve
hour shift, operated the machinery at each shaft, besides dumping the
cars; two men kept the 18 pumps on the line in order, the principal work
being in keeping the suction-pipes for the down-grade headings tight; thus
a force of 18 men was only required for the eight shafts. The cost of the
pipe, gates, etc., when put in place, was $14,631, and of the machinery
about $60,000.
[Illustration: FIG. 14.]
At the Idaho gold quartz mine, situated near Grass Valley, California,
water-power has been introduced during the past year (1883), taking the
place of steam. The supply main is of wrought-iron, 22 inches in diameter,
8,764 feet long, buried in the ground below frost-line. The joints, as a
rule, are riveted together, with occasional lead joints to admit of slight
movements in the pipe.[4] The pipe was coated by placing each joint in a
bath of boiling tar and asphaltum; to insure the most thorough coating, it
is necessary to keep the pipe for ten or fifteen minutes in the boiling
mixture. A cast-iron stop-gate is placed at the lower end of the main, and
also one at each of the branches. Cast-iron man-holes are attached to the
main, which, although they have given no trouble in this particular case,
are very objectionable for high pressures, as it is difficult to avoid
ruptures with cast and wrought-iron combined, owing to the great
difference in the elasticity of the two metals. The long seams of this
pipe are double-riveted, and the round seams single riveted; at the lower
end, iron of No. 6 gauge is used. From the end of the main, the water is
led to the several wheels by branches of smaller diameter.
[Footnote 4: With buried wrought-iron pipe this precaution is unnecessary,
as the elasticity of the iron will admit of the movement due to changes of
temperature, without injury to the rivets.]
The water is delivered at the hoisting-wheel with a total head of 542.6
feet. For power and for mill uses, etc., the required supply is about 8
cubic feet a second; this draught reduces the effective head to say 523
feet.
The work done consists in driving the following described machinery:
A large air-compressor--2 cylinders, double acting, air compressed to 75
pounds--requiring about 140 horse-power.
A line of Cornish pumps, forcing the water from a depth of 1,450 feet
vertical; 12-inch plungers for upper 800 feet, 6-inch plungers for lower
650 feet, with 6-foot stroke, requiring from 55 to 70 horse-power.
Hoisting from a double-compartment shaft--two connected winding reels,
moving separate cages--requiring 35 horse-power, or more.
A few small machine-tools and smithy forges, requiring 3 or 4 horse-power.
A 35-stamp mill, with concentrating apparatus, etc., requiring about 70
horse-power.
The total amount of power required being say 320 horse-power, for which
seven Pelton hurdy-gurdy wheels are employed.
The power in all cases is transmitted by systems of Manila rope belting;
the rope is 2 inches in diameter; the grooves in the sheaves or pulleys
are slightly oval, so that the rope does not go quite to the bottom; the
ropes are horizontal, and run very slack (no tighteners), with no
appreciable slip; the splices are made very long, to obtain uniformity in
diameter.
[Illustration: FIG. 15.]
This method of transmitting power appears to work most perfectly and has
given excellent satisfaction. It is thought, at the Idaho, to be greatly
preferable to the gearing formerly in use when the works were driven by
steam (for such work as pumping or hoisting, leather or rubber belting is
never used), besides being much cheaper in first cost.
The wheel driving the air-compressor is 6 feet in diameter, running 300
turns[5] per minute, with 1-15/18-inch nozzle; three ropes are used from
the wheel shaft to the counter-shaft, and six ropes from the latter to the
fly-wheel shaft.
[Footnote 5: The revolutions per minute, of these wheels, as here given,
are only approximate, as the design was to have the bucket speed=½
2(gh)^{½}.]
For driving the pumps, there are two water-wheels, set on the same shaft,
one 5 feet and the other 7 feet in diameter, either of which can be used
at will, thus permitting different rates of speed; two nozzles are placed
on each wheel, so that if necessary the power can at any time be doubled.
The smaller wheel has a 1-1/4 inch nozzle, and runs 360 turns a minute;
the larger has 1-1/8-inch nozzle, and makes 270 turns a minute. There are
two ropes from the wheel-shaft to a counter-shaft, and four ropes to the
fly-wheel shaft, on which is the pinion driving the spur-wheel attached to
the pitman of the pump-bob. Hoisting is done by two wheels placed side by
side on the same shaft, the buckets and nozzle of each wheel being placed
in opposite directions. Both wheels are 8 feet in diameter, with
15/16-inch nozzles, and make at full speed about 225 turns a minute.
Reversing the movement of the shaft is done by shutting off water from one
wheel, and turning water on the other wheel; the two water-gates for these
nozzles are quickly opened or closed by hydrostatic pressure, afforded
from the water main. In addition to the usual brakes on the winding-reels,
a brake is placed on the wheel-shaft, so that it can be stopped in a very
short period of time.
The shock to the pipe by the almost instantaneous cutting off the water at
these hoisting-wheels (nearly one cubic foot per second) has not
apparently had any injurious, effect. To lessen this shock, a compensating
balance was designed, but which is not now in use. A wheel, of small
diameter, is used for the smithy, etc., running at a very high velocity.
The wheel driving the stamp-mill is 6 feet in diameter, makes 300
revolutions a minute, and is supplied through a 1-3/16 inch nozzle. The
head of water at this point is a few feet greater than at the other
wheels. Power is transmitted from the hoisting and mill-wheel shafts by
two and four ropes, the same as with the pumping rig. The amount of work
done, or of water used, has not been carefully determined; judging from
the indicator cards taken from the old steam-engines, the managers of the
Idaho believe that an efficiency of fully 80 per cent. of the theoretic
power of the water is obtained on the main driving-shafts of the
machinery. The substitution of water for steam-power has resulted in a
large saving of expense. Although the hills near by are covered with fine
forests, thus making wood cheap, and although a round price is charged for
water by the company furnishing it, the cost of the water is considerably
less than that of the wood formerly used as fuel. The cost of attendance
is altogether in favor of the water-wheels, which hardly require any
attention. The cost of the change from steam to water-power was
$46,496.32.
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