THE AMERICAN DREDGERS ON THE PANAMA
CANAL.
New York, February 14, 1885
OUR engraving represents one of the great dredgers now in use
on the Panama Canal. The contract for the ten miles of marsh work,
beginning near Aspinwall, was taken by Slaven Brothers, of this
city; the great machine is believed to be the most effective of
anything in the same line. It was built under the patents of Messrs.
H. B. Angell and H. H. Lynch. The machinery of the dredge is mounted
on a scow one hundred feet long, sixty feet wide, and twelve feet
deep. There are eight engines, arranged in four pairs, for operating
the machinery. The main engines are for driving the buckets which
do the digging, and are of 250 horse power, having Myers' adjustable
cut-off. The belt from the engine runs to the top of the bucket
tower to a pulley eight feet in diameter, which drives compound
driving gear, connected with the upper tumbler shaft, which is
ten inches in diameter. This shaft moves a thirty-six inch square
drum, over which the buckets pass when they dump their load into
the hopper. The bucket tower is forty-five feet high above deck.
There are thirty-eight buckets, with a capacity of one and a half
cubic yards each. From sixteen to eighteen buckets full of dirt
per minute are discharged into a hopper attached to a cast iron
elbow near the top of the tower. This elbow is five feet four
inches in diameter where it connects with the hopper, and thirty-six
inches in diameter where it connects at the lower end to the discharge
pipe, which is attached to the elbow. This pipe is made of boiler
iron and is one hundred and fifty feet long. The distance the
mud falls, the position in which it strikes, and the inclination
of the discharge pipe give the mud a velocity of from 1,300 to
2,000 feet per minute through the pipe, according to the kind
of material which is being dug and discharged. The discharge pipe
is supported by a derrick which stands on the scow. Water is pumped
into the hopper by a pair of ten inch pumps from the canal through
a seven inch pipe which passes through the bottom of the boat
and extends to the hopper, at top of bucket tower. A second pair
of engines of thirty horse power raise and lower the ladder that
supports the buckets; they are attached to a drum for that purpose.
There is a hinged joint in the ladder outside of the derrick,
for the purpose of operating one section of ladder independent
of the other. A half inch cable connects the drum to the outward
end of the lower section by two bails. The endless chain to which
the buckets are attached is made of horseshoe iron 1-and- 1/8
inches by 9 inches. Another pair of spud and gypsy engines of
thirty horse power is used for raising the spuds and feeding the
buckets. The dredger rests upon the spud, upon which it can be
revolved without stopping the dredging buckets, thus enabling
the operators to dig from side to side at will. A chute connects
with the hopper, and is boarded on the sides to prevent the mud
or water from falling upon the deck. The fourth pair of engines,
also of thirty horse power, is connected to a windlass for snag
pulling. The engines are all supplied with steam from one set
of three boilers, and will require only about two tons of coal
each day. Six men, including a superintendent, run the entire
machine. Capacity of the dredger, 1,000 cubic yards per hour.
The cutting of the canal is to be 100 feet wide at the bottom,
185 feet at the top, and 27½ feet deep.
A correspondent of one of our city papers, resident in New
York, who has just returned from a visit to the works of the Panama
Canal, writes:
The canal is an assured fact. The French seem thoroughly to understand
the work before them, and have made admirable preparations to
cover all contingencies. They take the greatest care of their
employer, and their hospital service is unsurpassed in the world.
A force of over twenty thousand men is a good many to handle,
and, of course, entails a lot of red tape, but that seems necessary,
especially with Frenchmen. But they have a grand chief in M. De
Lesseps, and have now a splendid working staff in M. Diggler and
his officers.
I was very anxious to see the Scotch dredger at work in the
harbor of Colon, but it was not in operation during the eighteen
days I was there. [For engravings and description of this dredger
see SUPPLEMENT 491, April 5, 1884.] I was disappointed, as I wished
to compare it with our mammoth American dredgers. It cost, I understand,
£50,000, and is considered very good for deep-sea dredging,
but for actual work I saw nothing there to compare to our American
dredgers. I went on board and saw the latter work on many different
occasions, and was highly satisfied. The principle is unique and
very ingenious. The tower is iron, 75 feet high; the buckets and
chains are of steel, and each bucket will and does take up 1½
tons of earth each lift. The spud, on which the dredge rests and
revolves, enables it to take a sweep of 15 meters wide, and each
move of the spud moves her forward 18 feet, so that, like a mowing
machine, she cuts a swathe (to use a farmer's expression) 45 feet
wide, 18 feet long, and 9 feet deep on each movement forward.
They work perfectly, and it is indeed a grand sight to sit, as
I have done, for an hour or two at a time, and watch them working.
Rotten coral, roots, stumps of small trees, etc., all come up
with the dirt, and make no difference. Of course where rock is
struck, or hard coral, or an old petrified monarch of the forest,
blasting has to be done by the canal company ahead of us. Otherwise,
after the ground is cleared of vegetation, trees, etc., we simply
start in and eatliterally eatour way through with
absolutely no other preparation whatever, no men on shore working
ahead or any other way. What we take out goes through the dredger's
own discharge pipe on to the bank, and forms practically the bank
of the canal proper. We have now cut from the sea (the harbor
of Colon) three and a half miles of the canal by one machine,
and some ten miles up we have two other machines entering from
the Chagres River, cutting their way back to meet the first machine.
A fourth machine leaves here to-morrow, and will join the others
by the middle of January, while eleven more are building, and
will follow, one each six weeks or so, until all are fairly at
work. Our contract is for 30 million cubic meters, and will probably
lead to half as much again, as it is conceded by the canal company
and every one in the isthmus that nothing like our machines has
been seen or used anywhere. One instance of their capacity I saw
myself. A Suez dredger was put to work at a certain spot. After
fifty days she was withdrawn, and one of ours took its place,
and did in five days as much as the other had done. Our machines
cost about $125,000 (say £25,000), and require about 20
men to work them.
Panama Canal
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