November 19, 1915.

THE COLLIERY GUARDIAN.

1029

d = sag in feet under the worst conditions as calcu-
lated from the usual formula d =

8 »

Where I = span length in feet.

i; tv - resultant of weight and wind pres-
sure in in. (per foot).

S = tension in conductor in lb.

if, - corresponding sag at same temperature when
wind and icfe arts removed;

w, = weight per ft. of.wire Only.

M = modulus of elasticity . (say; 1R ,000,000).

A = cross section of wire in sq. in;

Then, to find d,, use the formula
u-, ____________w____64 (d, 2 — d2) M A

d —	31*

From d, it is possible to find the sag d2 at any Other
temperature from the formula :—•

f — f = 8 (fZ-’2 ~ d\ *1 + £ , /]—

(3 1‘ 4-8d, 2)c MAc \	d2/

Where t, = temperature in degs. Fahr., with sag,
t2 = any other temperature in degs. Fahr.
d2 = sag at temperature.

c = coefficient of expansion per deg. Fahr.

Modulus of Elasticity.

An examination of the stress strain curve of any
hard-drawn copper wire will show that the modulus
must be constant for the particular size, since the curve
is a straight line up to the elastic limit, but the modulus
is not necessarily the same for different sizes of wire.

In making measurements for true modulus values, it
is necessary to work on long lengths of wire, which
approximate to the span length employed on a tramway
or other overhead line, since this method would tend to
eliminate sources of error.

The Engineering Standards Committee’s Report
No. 55 stated that the values of the “ apparent moduli
obtained on the first application of the load would be
of interest and use, since it is these which must be taken
into account in the erection of long lengths of wire.”
This statement, however, is objected to, because in all
well constructed overhead lines the wires should, first be
strained to a tension higher than that at which they will
be permanently bound in, in order to get rid of kinks,
and to allow the wires, especially stranded conductors,
to ‘‘settle down.” This preeedure makes it permissible to
take advantage of the real modulus value, which may, on
the average, be considered as 18,000,000, instead of the

, I.

—-"V	---’

Large Locomotive for

the Natal Coal Traffic.

usual text book figure of 16,000,000. It will, however,
hardly be practicable to embody a minimum modulus
value in ordinary specifications of hard-drawn copper,
in view of the difficulties and delays which would occur
in most works in carrying out the sensitive tests
required. In special cases, however, it might be
advisable to specify a minimum value, and to make
arrangements with the National Physical Laboratory, or
other testing institutions to provide the necessary
apparatus, and carry out the tests on specimens
provided for the purpose.

Tensile Strength.

An interesting point arises out of the widely held
belief that the strength of hard-drawn wire lies in its
skin being hardened during the drawing process. An
examination of the matter does not disclose any con-
clusive evidence in support of this theory.

Effect of Temperature on the Strength of Hard-Drawn
Copper.

The question of the maximum permissible tempera-
ture of hard-drawn copper is of importance on overhead
power lines, because of the effect of heat in reducing its
tensile strength. The National Physical Laboratory
found that, on wires up to 0-194 in. diameter, the
reduction in breaking load due to temperature appears
to be approximately one-tenth of one per cent, of the
breaking load at normal temperature per degree Cent,
rise of temperature. The results of the speaker’s own
experiments seem to confirm that the determination will
hold good for all sizes of circular copper wire.

A number of experiments have been carried out by
Dr. F. J. Brislee to determine the permanent effects
of prolonged heating on the strength of wire, from which
it appears that with 1/0 S.W.G. trolley wire, the
permanent decrease in strength after two hours heating
at 150 degs. Cent. (302 degs. Fahr.) is only 0-5 per cent.,
while a 4/0 S.W.G. wire was not affected after four
hours. Among tramway engineers, it is generally
understood that the temperature of trolley wires never
exceeds 220 degs. Fahr, (say, 105 degs. Cent.), and it
is a fair deduction from the above tests that the limiting
temperature is not reached. In view, however, of the
fact that the temperature rise occurs on wires while
under strain, it would not appear to be advisable to
exceed a temperature of 250 degs. Fahr, in practice.
At this temperature the tensile strength of the wire
would be about 10 per cent, less than at normal tempera-
ture, but the strain would be relieved by the expansion

due to heating. The Engineering Standards Com-
mittee’s Report No. 55 gives the coefficient of
expansion of copper per 1 deg. Cent, as varying between
0-0000163 and 0-0000167. The average of these is equal
to 0-0000093 per 1 deg. Fahr. The voltage drop due to
resistance would appear to ■ be the limiting feature in
overhead wires rather than the question of temperature.
In case it should be necessary to know the resistance of
copper resulting from change of temperature this
formula may be used

R, = R (1 + 0‘0042£).

Where R “ the resistance at odegs. Cent.

If' —	„	t degs. Cent.

LARGE LOCOMOTIVES FOR THE SOUTH

African coal traffic.

A new series of exceptionally large and powerful
locomotives,- of the Mallet articulated compound type,
has been designed by Mr. £). A. Hendrie, the chief
mechanical engineer of the South African Railways, and
built by the North British Locomotive Company
Limited, of Glasgow.- These locomotives are primarily
intended for the haulage of the {fatal coal traffic over
the heaviest sections of line, and also the general freight
traffic to and from the Rand district. The locomotives
are of the 2-6-B-2 wheel arrangement,- the front group
of wheels being driven by the low-pressure' cylinders,
31/in. diameter and 26 in. stroke, whilst the rear group
is driven by the high-pressure cylinders, 20 in. diameter
by 26 in. stroke. Steam is distributed to all of the four
cylinders by Walschae-rt’s valve gear, actuating piston
valves working above the cylinders. The front bogie
wheels are 2 ft. 4|in. diameter, the coupled wheels 4 ft.
diameter, and the hind wheels 2 ft. 9/ in. The rigid
wheelbase is 8 ft. 8 in. and the total engine wheelbase
is 43 ft. 7 in. The boiler is of very large proportions,
and, with the superheater, contains 3,827 sq. ft. of
heating surface. The firegrate area is 53 sq. ft. At
50 per cent, of the working pressure (2001b. per square'
inch) the tractive force is no less than 43,3301b. A
system of spring equalisation is provided which
embraces the springs of the bogie wheels at front and
rear. These wheels have their springs connected with
those of the foremost and hindmost coupled wheels.
The engines are fitted with a change valve, which
enables them to be worked either simple or compound,

at the will of the driver. There is also a steam brake,
and the tender is fitted with the automatic vacuum
brake. Although these engines are built for the 3 ft. 6 in.
gauge (the South African standard), they have each an
adhesion weight of no less than 106 tons, and the weight
in working order is 128 tons 5 cwt. The tender is
carried upon two four-wheeled bogies, the wheels of
which are 2 ft. 9/ in. diameter. The bogie wheelbase is
16 ft. 9 in. The tank has a carrying capacity of
4,250 gals, of water, and 450 eu. ft. space for coal. In
working order, the tender weighs 51 tons 8 cwt.
Engine and tender combined have a weight, in working
order, of no less than 179 tons 13 cwt. 1 qr., a wheel-
base of 70 ft. 10|in., and a total length of 81ft. 2 in.
over buffers. The photograph is of additional interest,
inasmuch that it shows one of these Mallet type loco-
motives, the largest and heaviest railway engines ever
built in Great Britain, alongside one of the Pechot
articulated engines recently built at Glasgow for the
French military railways. These engines have each a
weight of 13/ tons, a heating surface of 288sq. ft., and
a tractive force (at 75 per cent, of the boiler pressure)
of 4,4501b.

The awarding of the Nobel Prize for physics for 1915, by
the Swedish Royal Academy of Science, to Prof. W. H.
Bragg, M.A., D.Sc., F.R.S., of University College (jointly
with his son), for an examination of the formation of
crystals by X-rays, renders of special interest the announce-
ment that Prof. Bragg is to deliver the 1916 May lecture
before the Institute of Metals on the subject of the structure
of metal crystals as revealed by X-rays.

The Acting British Consul at Honolulu (Mr. G. H.
Phipps) reports that a Honolulu company, which practically
holds a monopoly of the coaling business done at that
port, has recently made a contract with a New York firm
for the construction of a new coal handling plant on the
western side of the harbour, adjoining the course of the
proposed Kalihi Channel. The storage capacity of this new
plant is to be some 60,000 tons at the outset, and it is
contemplated to increase it ultimately to 200,000 tons. The
present plant, which has a capacity of only 30,000 tons, has
become wholly inadequate to cope with the large increase of
steamers calling for bunkers, consequent on the opening of
the Panama Canal. The coal supplied comes exclusively
from Australia and Japan. The new plant is to be up to
date in every respect, and the entire system is to be
electrically operated. Work has already been begun, and
it is hoped to have the plant in operation by the beginning
of July 1916.

PROBLEMS OF THE SOUTH LANCA-
SHIRE COAL FIELD.

MANCHESTER GEOLOGICAL AND MINING
SOCIETY.

(Continued from page 977./

DISCUSSION.

On the motion of the Chairman, seconded by Mr.
Wordsworth, a vote of thanks was accorded Dr.
Hiekling for his address.

Mr. Stanley Atherton said he was particularly struck
by the reference to the Wigan smash, and he would
like to know whether the author had taken the ordnance
without any outside observations for one end—-he
assumed that it was the Carriage rock there—and taken
the Upholland rock at the other end by quite a different
process. Some years ago he (Mr. Atherton) came to the
same conclusion as Dr. Hiekling, but he worked on a,
different basis. The two certainly seemed to bear a
very great resemblance to each other. Accepting that
the Carriage rock was similar to the Upholland rock, and
using that as a basis, he should like to ask the author
to tell them whether, in the Manchester smash, he had
come across anything -that really compared. There
seemed to be quite a resemblance between the two ends.
The Radcliffe field was very much broken up with
smaller faults, and he did not agree with Dr. Hickling’s
description of the part immediately north of Heaton
Park. There was a resemblance between the North
Radcliffe series and the Upper Irwell and lower portion
of the Manchester smash, and if, from field work, the
doctor had definitely decided any points, he should be
most happy to compare notes with him.

Mr. J. Gerrard said that, from what the lecturer had
told them, it was practically hopeless to seek for further
coal measures until they got some miles to the south
of New Astley. There were no borings in that particular
area that he was acquainted with. A test boring was
put down about | mile to the south of New Astley:
it went down about 400yds., and, as nothing was found,
it was given up. He gathered now that, if the boring
had been continued 200 or 300 yds. further, it might
have struck the coal measures. That was extremely
interesting, because it indicated the area within which
an examination should be made.

Dr. Hickling said there was no doubt whatever there
were coal measures which did not appear on the original
Geological Survey at all. There was, in fact, a coal
measure which was reached, very near the surface, in
a borehole on the site of the High-street baths of the
Manchester Corporation, about a mile from that
University, and it was again exposed in the railway
cutting near Fallowfield Station, a few miles out of the
city. That coal field was actually exposed to the
surface, and it followed that -there must be coal very
near the surface in that area. There might be, at the
maximum, a thousand feet of red rocks just above the
coal measures, but nowadays that would not stop the
sinking of an important colliery.

Mr. Gerrard remarked that the thickness of the red
rocks was not the only point to be considered; the
important question was the proximity of workable seams
to the base of the red rocks. A colliery owner would not
care to sink through 3,000 ft. of comparatively worthless
upper coal measures in order to get in touch with
workable seams. The author’s prognostication, as he
understood it, was that there were workable seams
within a reasonable distance of the base of the red
rocks.

Dr. Hickling replied that it was quite clear that, in
that area at any rate, there was no great thickness of
upper coal measures; and it was extremely improbable
that a greater thickness of upper coal measures would be
met with than existed above the Bradford Four-foot at
Bradford.

Mr. J. Lomax suggested that the statement that the
denudation of the upper coal measures occurred before
the deposition of the red sandstone was based on an
assumption formed from the knowledge they already
possessed of the unconcealed portion of the coalfield.

Dr. Hickling replied that it was more than an
assumption; it was based on actual facts.

Mr. Lomax asked whether that meant there were no
upper coal measures, so far as thickness was concerned,
like there were in Staffordshire.

Dr. Hickling said he had gone as far on that matter
as he could go at the present time.

Mr. Wordsworth said that, assuming the basin theory
was correct, would not one expect, in getting from the
north towards the centre of the basin, a flattening in the
inclination of the seams?

Dr. Hickling : In general, certainly.

Mr. Wordsworth contended that, as a matter of fact,
it was not so; it was rather steeper than flatter. That
could be seen if they went two or three miles along the
Irwell Valley fault. At Pendleton they went down,
roughly, 3,000 yds. from north to south, and that would
take them nearly into the centre of the basin. It was
steeper on the dip than it was to the rise.

Dr. Hickling said it was a very interesting point, and
just the kind of information he was anxious to have. He