May 28, 1915.

THE COLLIERY GUARDIAN

1117

in the hole, and a great many holes and steels were
lost, whereas the chisel or flat bull bit could readily
be removed, and drilled equally as fast in this rock.

James A. Mcllwee, in commenting on the results
obtained by him with Jackhamers in the sinking of a
shaft in Utah, stated that if machines of this class are
not mudding properly, . the difficulty can often be
overcome if the operator will occasionally raise the
machine and steel so that the bit is about 6 in. from
the bottom of the hole; this will permit the air to
blow through the steel and remove the mud from the
bottom of the hole. Especially in drilling deep holes
was this practice followed. He found that the “ rose ”
or 6-point bit was a failure in this shaft, whereas a cross
4-point bit, with a liberal clearance between wings,
turned the trick. The ground in this case was hard
quartzite, and it was necessary to temper the steel in
cyanide of potassium so as to protect the corners.

The Use of Blunt Steel.—In the south-west there are
a great many self-rotating hand-hammer drills operating
•by steam, in soft rock, and occasional trouble was
experienced until a suitable bit had been found. In
one very puzzling case, where the rock was a very
soft limestone, 6-point bits were at first tried, but as
satisfactory results could not be obtained, the standard
4-point cross bit was resorted to, and while consider-
able improvement was noted, it was felt that the
results could be improved upon. The cross bits were
made, and then blunted to retard the cutting action,
and this successfully solved the problem. In rock as
soft as that in question, sharp 6 and 4-point drills too
rapidly, causing the cuttings to wedge around the
steels just above the bits and interfere with rotation.

In the shaft of the Butte Alex. Scott Copper Com-
pany, which was driven through hard and almost dry
granite, 18 to 22 holes, 5 ft. to 6 ft. deep, were drilled
in 3J to 4 hours’ time, including the time consumed
blowing holes out and blasting, and during March of
this year, 101 ft. of shaft was broken, although opera-
tions were not conducted during 17 shifts of the month.

Here difficulty was experienced in keeping the hole
in the steel open, and the same method resorted to as
that already described to overcome the difficulty. The
hole was drilled in the hollow steel at a point 2 in. to
3 in. above the end of the bit, and the mining company
states that they are able to drill 7 ft. holes, and but
very seldom experience trouble from plugged steels.

Punching the Hole in the Side of Hollow Steel.—
Fig. 4 shows the manner in which the hole is punched
in the side of hollow-drill bits, and the style of punch
used in doing the work. The punch, if dressed as
shown at the top, makes the job easy of accomplish-
ment and ensures the closing of the hole in the end of
the bit. The hole is punched part way, and the punch
withdrawn and cooled in water. It is then inserted
once more, and becomes sufficiently heated by the time
it reaches the natural hole in the steel to take on a
slight curvature. The bevelled edge of the punch leads
it into the hole, as shown, forcing the metal just for-
ward into the hole that leads out the end.

Fig. 5.

Carr Bits.—A recent contribution to the solution of
the drill bit problem is that of the Carr bit. This bit,
while designed primarily for overcoming certain diffi-
culties in drilling rock, has been found to meet satis-
factorily, not only these special conditions, but the
ordinary conditions as well. The Carr bit has but a
single cutting edge, and is uniform and symmetrical in
shape. A transverse recess is formed across the centre
of the bit. With hollow steel this recess is tapered until
it runs into the original hole through the steel. With
solid steel the recess extends back about in. from the
face. This recess tends to act as a pilot, and reduces
the cutting or contact surface with the rock to a mini-
mum. The thickness of the bit is made equal to the
short diameter of the steel, and the length equal to the
bit gauge. Hollow drill steel bits are conical in shape
and have a 5 degs. taper on a side. Solid steel have
straight, parallel, cylindrical sides (fig. 5).

The advantages claimed for the Carr bit are :—It
holds its gauge better than the bits familiar to the
trade; thereby increasing the depth to which a hole
may be drilled before having to change steels. This
reduces the number of steels dulled per shift. It drills
a round hole and rotates easily-. It does not require
more than in. variation in the gauge of bits on
successive lengths of steel, thus avoiding, the use of
large diameter bits, and therefore reducing the amount
of rock to be cut. The bit is very simple in form and
very easily made, either with hand tools or in the
patented Leyner sharpener equipped with Carr dies.

The idea of drilling a hole the same size from the
collar down to the bottom originated with the inventor,
from the discovery , that a drill bit cuts a margin of
clearance for itself, so that the problem became one of
designing a bit that would effectually resist loss of
gauge, would drill a round hole, and cut rapidly. To
ensure the drilling of a round hole, the shape of the bit
was made such that it would be impossible for it to go

down if the hole were not round. The next problem
was to overcome the loss of gauge. This was done by
providing the long shoulders curved concentric with the
axis of the bit. This, combined with the other feature
necessary in drilling the.round hole, formed a large area
on the . shoulders. The hole being round, and the bit
being round, it simply rotates in the hole like a shaft in
a' boxing. Rapid cutting speed was assured by forming
the transverse'recess in the centre of the bit, for the
purpose of reducing the area that comes in contact
with the rock.

Fig. 6.

After the above had been done, it was discovered
that the harder the blow delivered to the steel and
transmitted to the rock, the larger would be the hole cut
by the bit. This was overcome by making the bit
more blunt, or with less cutting edge pitch, and it was
then discovered that the blunt bit would cut faster than
the sharper pitch, as it would reduce the rock in the
bottom of the hole by crushing a larger area and
absorbing absolutely all of the blow to advantage, as
there would be no slipping or sliding off of knots or
lumps in the bottom of the hole..

A test of the Carr bit by the Alaska Treadwell Gold
Mining Company with a Bull Moose type of Jackhamer,
as against the cross bit with the same machine, showed
about 20 per cent, more drilling for the Carr bit, while
on the regular Jackhamer the Carr bit did about a third
faster drilling than did the Cross bit under identical
conditions.

STORAGE BATTERY LOCOMOTIVES.*

By Stewart S. SHiVE.f

As a means of underground transport, locomotives are
little used, in British mines. The folloiving paper,
ho'wever, is of general interest, in that it gives
directions for testing the efficiency of storage
battery locomotives under varying conditions.

In many places where the mine is level or grades are
favourable, and where the haul is not extremely long, a
storage battery locomotive offers decided advantages
over a cable reel locomotive in the points of cost of
operation. Ruggedness, durability, and ease of upkeep
are the factors of prime importance in a storage battery.
The two batteries most extensively used for this pur-
pose are the Edison and the Ironclad Exide batteries.

The most recent storage battery locomotive for mine
haulage is represented by the installation in the Grant
Coal Mining Company’s mines at New Goshen, Ind.
The six 5-ton locomotives in operation at this place are
giving satisfactory service. One of these locomotives is
equipped with two motors; one motor driving on each
axle through a four-lead steel worm meshing with the
34-tooth bronze worm-wheel, the whole being enclosed
in a housing around the axle. The battery equipment
consists of 63 A-8 Edison cells, which have an average
discharge of 75 volts at normal discharge rate of 60
amperes. The motors operating in parallel and driving
through gear reduction 16in. diameter wheels, gives the
locomotive a speed of 4-3 miles per hour at normal dis-
charge rate. The locomotive is equipped with a series
and parallel controller, so that on starting the motors
may be connected in series, and under these conditions,
with twice the normal discharge rate, nearly 120
amperes, the locomotive will exert a tractive effort of
2,2901b. The brake mechanism is of the automatic
screw locking type.

In the panel system of mining at the Grant mine, the
storage battery locomotives are used for distributing the
empty cars to the rooms, and hauling the loaded cars
from the rooms to the double parting on the panel entry.
The cars are gathered from the rooms and taken, to the
double parting in trips averaging about 14 cars each,
and from this double parting they are taken to the shaft
bottom by a trolley locomotive. The weight of an
empty car is 1,6001b.; the load weighs 3,600 lb., making
the total weight of a loaded car 5,2001b.

The average number of 14-car trips made by each
locomotive per day of eight hours is 16, making 224 the
average number of cars handled per day for each loco-
motive., Of these 224 cars, there is an average of six
cars per day that are loaded with dirt. On this basis,
each locomotive hauls out 392 tons of coal per day,
making a total of six locomotives of 2,350 tons per day.
The actual output over the tipple for the four locomo-
tives is about 2,200 tons per day.

In hauling a trip of 16 cars to the shaft bottom,'
the current consumed while operating on level track
was noted to be 90 amperes. The current, when pulling
this trip up a grade of about 1 per cent., was noted to be
160 amperes, and in going around a curve which was
up a grade of about 1| per cent., it was noted to be
220 amperes. The discharge rates of 160 amperes and
220 amperes were maintained for only short intervals,
while the discharge rate of 90 amperes was maintained
ouite constantly when hauling this trip. The:normal
discharge rate of 63 A-8 Edison cells is 60 amperes, so

* Abstract of a paper read at the Illinois Mining Institute,
f District manager, Jeffrey Manufacturing Company.

that the above discharge rates are not excessive for the
battery capacity of these locomotives.

. The oldest of these locomotives, has been in opera-
tion for more than a year, and the total cost of these
repairs has not exceeded 5 dots. It is only after a year
of continuous service that it will be necessary to replace
the electrolyte in the battery. The battery must be
charged every night, and as the daily work which the
battery performs varies, its condition of discharge at
the end of each day will vary, and therefore a different
amount of charge will be required to put the battery - in
shape for service on the following day. There, are two
methods by which the condition of the battery may be
ascertained : One is by means of the volt-ammeter j
which will indicate the voltage across the battery at any
particular rate of discharge. The other method is by
means of an ampere-hour meter, which records, by q.
rotating hand on the circular dial, the number of ampere
hours taken out of the battery.

Obviously the amount of electrical energy which it is
required to store in a battery varies with the amount of
work the locomotive must perform, and this depends
on the distance and the grades over which the load is
hauled. Therefore it is necessary that a correct battery
equipment be determined for each installation. The
size of battery with which it will be necessary to equip
a locomotive is derived from two separate considera-
tions, and the size of battery chosen will be a maximum
given by either one. First, the speed at which the
maximum drawbar pull must be developed furnishes a
basis on which to estimate the size of the battery. If
60 per cent, be assumed as the average over-all efficiency
of the locomotive, we may write the following equation :

(D.B.P.) x (M.P.H.) x 5,280 x 746 _ E J
60 x 33,000 x *60

in which D.B.P. represents the drawbar pull, M.P.H.
represents the miles per hour, E represents the voltage
across the battery, and I the. current discharge across
the battery. Transposing E in this equation, and
reducing, the following form is obtained for the current
discharge from the. battery.

I — 3’32 x	* M.P.H.)

E

The value of E will depend on the voltage available for
charging, upon the motor equipment of the locomotive,
or upon some special condition under which the loco-
motive must operate, such as a gaseous mine which
makes it desirable to have .a low-voltage, equipment. If
the value of the current thus obtained will be required
almost continuously, then a battery should be. selected
whose normal discharge rate is not less than half of the
current thus obtained, and preferably not less than this
value divided by 14. If the maximum drawbar pull
which the above value of current gives is to be exerted
intermittently, then the normal battery current will be
one-third of the value obtained, and if the maximum
drawbar pull is to be exerted momentarily, it is possible
to select such a battery that its normal discharge rate
will be only one-fourth or even one-fifth of the value
obtained from the equation. In general it will be safe
to so choose a battery that its normal discharge rate
will be one-third of the value calculated:

.02

Curves Giv/ngr/C. Mi firs. Pegu ire of af Battery
Per Ton of LocomotePe ana/Per 'Ton of
Loaded Train Per /OOO f£ef of t/au/
('nc /uc/ingr Lie turn Trip) Tor Various .
Graefes fP/'i/t ano'Pgratns/Loaded Cars /, /



/ 2.3*4 f 6 7 B ? /O /T /2
Per CentGraefe

The next step, which is the calculation of the size of
battery on the kilowatt-hour basis, is by far the more
important, and is really the way in which the size of
the battery in most cases will be determined, unless, in
order to develop the necessary drawbar pull from the
battery determined in this way, the current discharge,
from the battery will be top greatly in excess of. the.
normal discharge rate. The power taken from the
battery may be divided into two parts, namely, that
required to haul the train of cars, and that required to
haul the- locomotive. By this means, it is possible to
reduce the entire route over which the locomotive and
cars travel to an equivalent length of haul for the loco-
motive and an equivalent haul for the. train. An
over-all efficiency of 60 per cent, is assumed ,for the
locomotive, a rolling friction of 201b. per ton for the
locomotive, and 301b. per. ton for the cars. ; For. each
per cent, of grade an additional tractive effort of. 20 lb.
per ton is required for both locomotive and cars. The
ratio of the weight of-an empty car to the weight of a