At a recent meeting of the Engineers' Club of Philadelphia, Mr. John C.
Trautwine, Jr., exhibited and described drawings of a large land dredge
built by the Osgood Dredge Co., of Albany, New York, for the Pacific Guano
Co., to be used in removing 8 to 15 feet of material from the phosphate
rock at Bull River, S.C.
The more prominent features of the machine are the car-body, the water
tank, boiler and engine, the A frame (so-called from its slight
resemblance to the letter A), the boom, the dipper-handle; and the dipper,
drawings of which were shown and described in detail.
Before the excavation is begun, the forward end of the car (the end
nearest the dipper) is lifted clear of the track by means of 3
screw-jacks. When the machine has excavated as far in advance of itself as
the length of the boom and that of the dipper-handle will permit, say
about 8 feet, the car is again lowered to the track, the screw-jacks
removed, and the car is moved forward about 8 feet by winding the rope
upon the drum, the other end of the rope being attached to any suitable
fixed object near the line of the track. The forward end of the car is
then again lifted by means of the 3 screw-jacks, and the digging is
resumed. The machine cuts a channel from 25 to 35 feet wide, and deposits
all the dirt upon one side. If necessary, it can dump earth about 25 feet
above the track. The miners follow in the wake of the machine, getting out
the phosphate as fast as it is uncovered. When the machine reaches the end
of the field it is lowered to the track and the screw-jacks are removed.
Shoes or skids are then placed upon the track, and the wheels of the
turntable are run up on them. This lifts the end wheels clear of the
track, so that the car and machine rest entirely upon the turntable. By
now blocking the turntable wheels and winding up only _one_ of the ropes,
the car body and the machine are swung around end for end. The digging is
then resumed in the opposite direction, the temporary track, upon which
the machine travels, being shifted to one side, so that the second channel
is made alongside of the first. The earth removed in cutting this second
channel is dumped into the first channel, the phosphate (as stated above)
having been first removed.
The dipper is of plate steel, and holds 1¾ cubic yards of earth when even
full.
The machine is manned by an engineer, a fireman, and a dipper-tender,
besides which from five to ten laborers are required. These look after the
track, etc.
* * * * *