LOADING ROOM DUTIES.
=Making a telegraph joint.=—The insulation is removed from the ends for
1½ inches and the wires brightened. The ends to be joined are placed
across each other about one-third distance from the insulation, making
an angle of about 45° with each other. The wires are grasped firmly at
the junction and each free end wound tightly around the other wire for
four turns; the winding should be in opposite directions. The ends of
the wires are trimmed down so they will be smooth and present no sharp
points.
When wires are joined with brass jointers three-fourths inch of each
wire is bared and the wires are inserted in the jointer; each end is
crimped with pliers in the direction of the longer axis; the rest of
the jointer is crimped and the ends or sharp points rounded off. When
brass jointers are used care should be exercised not to crimp them
too hard, as the wires may be partly cut through and finally broken.
Special care must be used with the fuse leads, as the secondary circuit
of the mine transformer can not be tested after the compound plug is
assembled.
=Insulating a joint.=—A piece of rubber tape about 2 inches long is
used, with ends cut diagonally. The tape is stretched, and starting
at a point about three-fourths inch back on the insulation, with the
long edge of the tape on the inside, it is wound around the joint under
tension, each turn covering the previous turn about one-third. The
wrapping is continued until the same amount of insulation is covered on
each side, when the wrapping is worked backward over the joint and the
end is secured by pressing it firmly a short time or placing a drop of
cement under it.
=Making a water-tight joint.=—The two ends of wire are scraped clean
for about three-fourths of an inch and joined by a brass jointer,
which is then crimped. The insulation is scraped clean about 2 inches
on each side of the jointer and covered with rubber cement. (Cement
is not absolutely essential.) Two strips of rubber tape are cut about
6 inches long, with diagonal ends, and stretched. Beginning about
1½ inches along the insulation, the tape, with the long edge on the
inside, is wrapped firmly and tightly until about one-fourth of an inch
of the insulation on the other side is covered; it is wound back and
forth over the joint so as to taper toward the ends. The other piece
of tape is used, beginning at the other end and wrapping as before.
The finished insulation should be thick at the middle and taper toward
the ends. It should be firm and tight. The insulation is covered with
tin foil, wrapped with protective tape, and vulcanized for about 30
seconds. The protective tape and tin foil are then removed, the joint
inspected, and new protective tape wrapped on, using two pieces,
starting at opposite ends and finally ending each beyond the center.
=Making a Turk’s-head.=—The cable is trimmed square and a wrapping
of four or five turns of marline is made about 15 inches from the
end. The collar, flat side first, is slipped on until it rests on the
marline; the iron wires are bent back regularly over the collar. The
jute wrapping is unwound to the collar and trimmed, and all the iron
wires are cut with the pliers, removing all but 4 inches and 6 inches
from alternate strands; the iron wires are bent separately to fit the
collar closely (making two right angles with the pliers), and the ends
arranged smoothly along the cable; the end of a piece of marline is
engaged under one of the wires near the collar and wrapped regularly
and closely around the cable, and the free end of marline secured with
two half hitches. About 15 feet of marline are required for single
conductor cable; 24 feet for multiple cable.
=Testing fuses.=—The following apparatus is used for testing in the
loading room: A double-pole double-throw switch, a 150-volt voltmeter,
and sufficient dry cells to give a full throw when using the lower
scale of the voltmeter. The apparatus is connected up on the testing
table so as to make resistance measurements by the voltmeter method.
To test fuses, leads are carried from the switch to an iron or other
suitable receptacle outside of the building and the fuse leads joined
thereto. A full deflection should be obtained when the circuit is
closed through the fuses.
=Preparing a compound plug for service.=—The transformer to be used is
first tested for a good circuit between the red wires, a poor circuit
between the ends of the black wire, a good circuit between the black
or primary lead and the reactance terminal, no circuit between the red
and black wires, and no circuit between any wire and the case. The
resistance of the circuits is determined by the voltmeter method. The
upper end of the black wire (see fig. 8) is prepared for use by baring
the wire for about one-half inch and securing it to the binding post in
the neck of the transformer. The ball seat is screwed home. The spring
plate, distance ring, and ball are placed in the circuit-closer cap,
which is held inverted and the transformer screwed into it, the threads
being coated with ruberine.
(_a_) =Old model, brass fuse can.=—Starting with the compound plug
dismantled.
A piece of loading wire is cut about 3 feet long and the ends bared.
One end is joined by a telegraph joint to the primary terminal of the
transformer and the joint is taped. This wire and the two secondary
wires are drawn through the fuse can, which is screwed on the
transformer, the threads of the latter having first been coated with
ruberine.
Two mine service fuses, which have been tested for continuity of
circuit, are connected in multiple across the secondary (red) terminals
and the joints taped.
The can is held vertically and the explosive, if trotol, poured in
up to the screw threads for the fuse can cap; if dynamite, inclosed
in a cloth bag and placed in the can. The fuses are embedded in the
explosive.
The loading wire is drawn through a lead washer and the fuse can cap;
the latter, its threads having been coated with ruberine, is screwed
into place.
A rubber packing is pushed over the loading wire into the stuffing
box in the fuse can cap, a brass gland is threaded down so that it is
close against the rubber packing, and the follower is screwed home with
moderate pressure. The lower tube is screwed into place, compressing
a lead washer between it and the fuse can cap. The threads of the
follower and lower tube are coated with ruberine.
The loading wire is drawn through a lead washer and the hole in the
plug proper, and the latter screwed hard against the lower tube.
A rubber packing and a brass gland are placed upon the loading wire and
forced into their seat in the plug proper by means of the follower, the
threads of which have been coated with ruberine.
(_b_) =Rubber fuse can.=—Starting with the compound plug dismantled.
Two mine service fuses, which have been tested for continuity of
circuit, are cut with 9-inch leads, wires bared for about 1 inch and
connected in multiple. A piece of loading wire is cut about 3 feet long
and the ends bared for telegraph joints. It is threaded through a hole
in a cake of dry guncotton. The two fuses are inserted by pushing each
separately into the same hole and the loading wire drawn up until it is
the same length above the cake as the fuse leads.
Three other primer cakes are threaded on the wire; two above the fuses,
and one below. This arrangement will leave the fuses in the third cake.
The cakes are held in one hand with the fuse leads upright, and the
fuse can slipped over the cakes, being careful to thread the fuse leads
and loading wire through the opening.
The screw threads of the fuse can cap are covered with ruberine and it
is screwed firmly into place onto the fuse can. The stuffing box of the
cap is assembled.
The plug proper is held upright in a vise. The fuse can, the threads
of the cap having been coated with ruberine, is screwed home and
secured by its set-screw. The loading wire must be pulled through the
opening in the plug proper with extreme care. It must not be injured
in placing the fuse can in position and in screwing it home. The
transformer leads are cut about 6 inches long, and the ends bared for 1
inch. The brass collar is screwed on the transformer; a little ruberine
on the screw threads facilitates the operation. The connecting collar
is slipped over the fuse leads and loading wire and allowed to rest
on the fuse can. The transformer is supported by allowing two of the
connecting bolts to slip into the holes in the collar; telegraph joints
or brass jointers may be used between the secondary leads and the fuses
and between the primary lead and the loading wire. The joints are wound
with rubber tape, care being taken that there are no sharp ends to cut
through the tape.
The transformer is raised vertically above the fuse can until the lead
wires are extended. It is lowered and at the same time the leads are
coiled in the base of the transformer. As the transformer and collar
approach their position on the connecting bolts, the connecting collar
is screwed on the transformer, the threads of the transformer having
been covered with ruberine. The connecting collar will take care of
the remainder of the leads and joints. The set-screw in the connecting
collar is screwed home; the brass collar is placed on the connecting
bolts and secured in position by the nuts and cotter pins.
The lips of the fuse can and connecting collar are covered with a
thin covering of rubber cement. A piece of rubber tape is cut about
18 inches long and laid around this opening without stretching. A
piece of protective tape is cut about 18 inches long and laid over the
rubber tape with considerable stress. This forces the soft tape over
the lips on the connecting collar and the fuse can and makes a tight
but flexible joint. The stuffing box in the plug proper is prepared as
under (_a_).
Great care must be taken not to injure the insulation of the loading
wire in tightening up the follower in the stuffing box of the fuse can
or of the plug proper.
(_c_) =Trotol fuse can.=—Starting with the compound plug dismantled.
Two mine service fuses, which have been tested for continuity of
circuit, are cut with 12-inch leads, the wires bared for 1 inch and
connected in multiple. A piece of loading wire is cut about 3 feet long
and the ends bared for telegraph joints. The loading wire is threaded
through the fuse can and cap. The threads of the fuse can are covered
with ruberine. The can is screwed into the cap. The threads of the
connecting collar are coated with ruberine and the collar is screwed
down entirely. The loading wire should project about 4 inches above the
connecting collar. The stuffing box of the cap is prepared. The plug
proper is held upright in a vise. The fuse can cap, its threads having
been coated with ruberine, is screwed firmly into the plug proper by
means of a spanner wrench. The loading wire must be pulled through the
opening in the plug proper with extreme care. It must not be injured in
placing the fuse can in position and screwing it home.
The fuses are inserted in the fuse can, which is filled with trotol
to the top of the connecting collar. The transformer leads are cut 4
inches long and the ends bared for 1 inch. The threads of the brass
collar are covered with ruberine. It is screwed on the transformer.
The latter is raised vertically above the fuse can and lowered on the
connecting bolts.
Telegraph joints are made between the secondary leads and the fuses
and the primary lead and the loading wire. The joints are wound with
rubber tape, care being taken that no sharp ends cut through the tape.
The leads and joints are coiled in the base of the transformer. The
connecting collar, its threads having been covered with ruberine,
is screwed upon the transformer against the brass collar. The
bolt-securing nuts and cotter pins are placed in position. The stuffing
box in the plug proper is assembled as under (_a_).
The actual resistance of the assembled plug in the vertical and the
horizontal positions is determined by testing with a voltmeter.
In service, after the loaded plug tests out satisfactorily, all set
screws are set up.
When compound plugs are prepared for drill or for instruction purposes
the use of ruberine or other waterproofing material on the screw
threads is omitted; care must be taken that the transformer leads are
not needlessly shortened.
=Loading a mine.=—The mine case is carried from the storeroom to the
loading room and placed on a loading skid or other receptacle with
the loading hole up. The plug is removed and the screw threads are
thoroughly cleaned. The explosive detail brings in a box of explosive
from the explosive house and inserts a loading funnel into the loading
hole. The charge for a 32-inch mine case is 100 pounds of explosive.
For the larger cases, the charge should be the maximum that the
conditions warrant; it is specified at present as 200 pounds, though
larger charges are desirable if enough explosive can be obtained and
the excess buoyancy of the case will warrant the use of more than
200 pounds. The cartridges of dynamite, the trotol, or the blocks of
guncotton are inserted by hand and so placed in the mine case that
there will be ample room for inserting the compound plug. Only one box
of explosive for each mine being loaded is brought into the loading
room at one time. After the proper amount of explosive has been placed
in the mine case the screw threads are thoroughly cleaned with button
brushes and then coated with ruberine or other material to prevent
access of water. The compound plug, with its screw threads similarly
coated, is screwed home with the socket wrench, a lead washer being
used between the plug and mine case. A bar put through holes in the
sides of the skids and through the maneuvering ring will prevent the
case from falling over and from turning while the compound plug is
being screwed home.
In order to insure setting the compound plug tight, it is advisable to
tap the end of the lever of the socket wrench a few times with a large
mallet or a large wooden bar. The mine cap is bolted on and the mine
put in a tank for test. If time admits, it may remain in the water 24
hours. It should show practically the same resistance as the compound
plug. If this test be made, the loading wire must be long enough for
this purpose.
Upon completion of this test the mine is taken from the tank, the
loading wire pushed inside the cap to avoid injury in handling, and the
loaded mine taken to the planting wharf.
The precautions to be observed in handling explosives and loading mines
are given in Appendix 1.