1284

THE COLLIERY GUARDIAN.

December 18, 1914.

was trying to get some hydraulic tests made, but at
present he was unable to state the theoretical pressure
which they would stand.

Mr. E. E. Bramall (Leicester) said that he should
like to know the effect on the concrete props when a
crushing strain came on. Did the prop collapse
suddenly? If so, it seemed to him that there was a
risk that pieces of the sides would fly all about the
place, much to the danger of the men.

Mr. Hepplewhite did not think that there was any
danger of that. The props were so hard that they
could not drive a pick into them.

Mr. Bramall replied that that was exactly why he
anticipated the danger he had suggested.

Mr. Hepplewhite thought that if they would stand
in a Warwickshire mine, they would stand anywhere.
They were, as he had said, set alternately with
wooden props, and so far they had had no difficulty
with them, though it was only fair to remember that
they were at present merely in an experimental stage.

Mr. Bramall asked whether any of the props had
failed through crushing.

Mr. Hepplewhite said he believed that none of them
had collapsed.

Mr. Bramall said that he still felt that if such a prop
did collapse there would be danger in the pieces flying
off the sides.

Mr. R. Laverick (Nottingham) remarked that he had
been trying to get some information from the makers of
concrete props, and he had received a letter from them
in which they said that, granted the use of a first-class
aggregate and careful mixing and moulding, they were
justified in assuming that after two months in air, or
one month in a curing chamber, the concrete would
have a crushing strength of 2,400 lb. per sq. in. Based
on this, the ultimate load at which props would fail was,
by calculation, as follows :—3 in. props, 3 ft. long, at
nine tons; 4 in., 4 ft. long, 15 tons; 5 in., 5 ft. long, 25
tons; and 6 in., 6 ft. long, 42 tons. Taking cement at
40s., and the aggregate at 5s., the cost of a 3 in. prop
would be 10d.; 4 in., Is. 9|d.; 5 in., 3s. Ifd.; and 6 in.,
5s. 7|d.

Mr. Percy W. Lewis : Is that for material only?

Mr. Laverick answered that it was the full cost—for
concrete, aggregate, and labour, the last item varying
from 3d. to Is. per prop. The props were reinforced
by rods, and he thought that there was no doubt that
the concrete was less brittle and less liable to break
suddenly if it were reinforced than otherwise.

Mr. C. Dickinson (Netherseal) thought that there
would be a difficulty in getting the props out. It might
perhaps not be a very expensive matter to leave them in,
but there were many objections to such a course, and
he believed they would experience difficulty when the
men had to get them out. He did not think, however,
that there was as much in the question of a shortage of
timber as some of them thought. A couple of months
ago he got a little bit frightened, and bought some
French timber in 6 ft. 6 in. lengths. He found, how-
ever, that it could not safely be used in such lengths,
and he had had to cut it in half, and even then had
to issue a special warning about the use of the shorter
lengths. It was grown much more rapidly than Nor-
wegian timber, and seemed to possess very little
strength.

Mr. S. Evans (Creswell) enquired, amid some
laughter, whether Mr. Hepplewhite, with his experience
of concrete props, would recommend their use, provided
that an adequate supply of suitable timber was
obtainable.

Mr. W. Tate (Tamworth) thought that Mr. Hepple-
white had hit the nail on the head when he wrote that
“ the whole question resolves itself into adapting some-
thing, consistently with safety to the workers, that will
meet the roof depression and save the prop from
destruction.” Since the war began they had been
using again at his colliery some girder props which they
first tried some time ago. In a period of four months,
out of 153 props, two had bent, and two had broken.
They had been used, however, in a part of the pit where
the conditions suited steel props. If he had put them
elsewhere he should probably never have seen one of
them again.

Mr. G. J. Binns pointed out that before Canadian
timber could become commercially available, great
organisation, together with much skill and capital, would
be required. He did not think that there was much
likelihood of either Canadian or North American timber
coming into use in English collieries, and he hoped that
in the not very distant future they would experience the
same facilities for obtaining a supply of suitable pit
timber as they enjoyed before the war.

Mr. Bingley observed that the great difficulty with
regard to both Canadian and Russian timber was that
the money for cutting it down must be advanced before
anything could be done.

Mr. G. Spencer (West Hallam) said that some 15
years ago he had some cast iron props made by the
Stanton Ironworks Company. Some were perfectly
cylindrical, but others were bellied in the middle in the
belief that that would make them stronger. From

experiment and reasoning, however, he came to the con-
clusion that that was hardly necessary. They found—
and he did not see how they were going to prevent such
a thing—that the men, in their “ cussedness,” would
persist in hammering the props instead of the lid. They
had some of the props broken, and eventually they
discarded them. With regard to concrete props there
was no doubt that if a piece were chipped off, the prop
was to that extent weakened. He remembered seeing
some years ago in Leicestershire a brick-built pillar at the
pit bottom where all the coal had been extracted. The
bricks, however, kept crushing. Bits were broken off,
the pillar was weakened, so that more bits came off, and
it was weakened still further. Ultimately the pillar was
taken out and one of wood blocks substituted for it, with
entire success, for the more wood was compressed the
stronger it got. With regard to the tubular props,
which he mentioned at the last meeting, they were made
of old boiler tubes, and partially filled with sawdust,
with wooden discs at intervals. The discs had the effect
of forcing the sawdust to compress evenly right through
the prop, and they had answered very well indeed. He
had subjected some of them to a pressure of nearly 20
tons by hydraulic test, and the only effect was to com-
press them a little more. The men, however, would
continue to hammer the prop, and though he had a
slightly tapered lid, he thought that it might be an
advantage to use two lids, each of them slightly tapered,
so that they would act as a fold-wedge, and the props
could be tightened without hammering the tube at all.
The idea had occurred to him that, as a triangular-shape
was the strongest for the same materials, a prop might
be rolled with three sides, but having each side concave
instead of straight, to reduce the weight, and having the
corners rounded. He thought that that might form a
simple and cheap kind of prop, and he submitted the
idea for what it was worth.

The President moved a vote of thanks to Mr.
Hepplewhite for giving such a useful and interesting
paper on a subject of such great importance.

Mr. Spencer seconded, observing that the paper
embodied the accumulated experience of a good number
of years, together with the results of Mr. Hepplewhite’s
close observation.

The resolution having been heartily adopted, Mr.
Hepplewhite, in acknowledgment, said that his only
ambition was to assist them to the best of his ability.

MINING INSTITUTE OF SCOTLAND.

A general meeting of the Mining Institute of Scot-
land was held on Saturday afternoon last in the rooms
of the institute, 39, Elmbank-crescent, Glasgow. Mr.
James Hamilton, Glasgow, the president, occupied the
chair, and there was a particularly large attendance of
members. At the outset, Mr. A. M. Ritchie, colliery
manager, East Grange, Fife, was admitted a member
of the institute; while Mr. Robert H. Morris, genera]
manager, Jasper Park Collieries Limited, Alberta,
Canada, was added to the roll of associate members.

Rosehall Signalling Indicator.

The discussion was resumed on the paper previously
read by Mr. James Black on “ The Rosehall Signalling
Indicator.” Mr. Black gave an interesting demon-
stration with the device, and the discussion was after-
wards closed.

Fan Testing, with Special Reference to the Measurement
of Pressure.

The meeting thereafter proceeded to discuss the paper
by Mr. Thomas Bryson on “ Fan Testing, with Special
Reference to the Measurement of Pressure.”

Mr. John Watson, in the course of a written com-
munication, said it was desirable that further experi-
ments should be made in order to confirm the
conclusions arrived at by Mr. Bryson, or at any rate to
arrive at conclusions which would be perfectly definite
and readily accepted without question by everyone.

Mr. William Davidson, Glasgow, said the author
had put before them some very interesting statements
and figures, which must have taken considerable time
to gather. These, like all others previously published
on this subject, would require to be accepted, until
proved unsound or incorrect either theoretically or by
further tests. Apparently Mr. Bryson had made all
his experiments in a uniform airway, and he (Mr.
Davidson) would like to know whether the author had
investigated the effect in an airway of varying section,
and consequently varying velocities, with the different
types of gauges? From the paper which had been read
the velocities and the quantities would indicate that the
experiments were made with a small plant, to which
objection might be lodged, but on further consideration,
the adaptability and range of such a plant added
credence to the experiments. .

Prof. Burns, Glasgow, said that the experiments
referred to in the paper had been carried out on an
experimental fan in the Royal Technical College,
Glasgow. Since the paper was read the author had
carried out a further series of experiments, which to
his (the speaker’s) mind demonstrated, far more forcibly
than the previous tests did, the truth of his conclusions.

The discussion was adjourned until next meeting, and
it was remitted to the council to consider and report
upon the suggestion which had been put forward by
Afr. John Watson, Kilmarnock.

Tests on False Links for Cut Chain Braes.

The discussion was resumed on the paper previously
read by Mr. John T. Wight on ” Tests on False Links
for Cut Chain Braes.”

Mr. Henry Briggs, Edinburgh, wrote that tests of
the character Mr. Wight had conducted were useful in
furnishing information as to the reliability of existing
types of links, and in indicating which ought to be
discarded. Moreover, these tests would be of great
value to those striving to design a link to beat the
clumsy D form, which at present headed the field for
strength, and which — rather unexpectedly — also
furnished the most consistent results. Mr. Wight had
rightly pointed out the greater likelihood of the D-link
catching against projections, the effect being to throw
on the chain sudden stresses of possibly serious magni-
tude. Another point against the D-link was that, with
one exception, it was the link most likely to work
corner ways, i.e., with the pull transmitted diagonally
across the link, and it seemed to him (Mr. Briggs) that
in such a position the link would more easily fail. On
the whole, strong though that link had proved in the
testing machine, it would appear that more should be
“ written off ” the results for the contingencies of
service with the D-link than, perhaps, with any of the
other kinds tested. Mr. Wight, he gathered, did not
condemn the riveted link, providing that the sections
of the metal round the rivet holes, and of the rivets
themselves, were properly proportioned, and that the
riveting was skilfully done. Riveted links were readily
made, and were of rounded and regular shape. Their
serviceableness would, therefore, make it seem worth
while spending a little effort in improving them. The
tests brought out clearly two points in connection with
riveted links. The first was that the riveting was
better at the end than at the side; and the second was
that an inter-locking section strengthened the link. He
should like to suggest to the author the advisability of
making and testing a few links, which combined the
advantages of end riveting and an inter-locking section.

Mr. David Beveridge, Kelty, in the course of a
written communication, said the majority of the
members would be interested in the tests contained in
this paper. To his mind, the tests had been useful in
the following ways :—(1) They had proved which design
when carefully made was the strongest when new; (2)
they had proved that the less of the human element
required in the manufacture of these links, the more
reliable the link was likely to be 'according to its
design; (3) they showed how important it was that
the blacksmith who made these links should use the
greatest care in heating the iron, and making the link
a good fit; and (4) they also showed how several of the
designs could be improved in strength, while the
breaking point and several other details were conclu-
sively proved.

Further discussion on the paper was adjourned.

The Manufacture of By-Product Coke.

A paper was read by Mr. George S. Cooper, Sheffield,
on “ Notes on the Manufacture of By-Product Coke,
with Special Reference to the Hoppers’ Process.” In
the course of his introductory remarks, the author said :

By-product coking had not developed in Scotland to the
same extent as in the North of England. This could be
put down principally to two facts : first, Scottish iron-
masters have not been dependent on coke for their furnaces
on account of splint coal being available; and, secondly,
much of the Scottish coal as mined at present offers certain
difficulties to its treatment in by-product ovens. According
to the general report of the Chief Inspector of Mines for 1912
(the latest available official information) there were in opera-
tion in Scotland 861 beehive ovens and 417 of other types,
including 348 of the by-product type. The production of
coke is given as follows :—Dumbarton (including Ayr and
Linlithgow), 68,119 tons; Lanark, 203,111 tons; Stirling,
356,572 tons—total, 627,802 tons. It would be seen that
the coking industry was of substantial importance in con-
nection with coal mining in Scotland, and the writer
believed he was correct in saying that the extension of the
industry in Scotland is occupying the minds of many colliery
owners in the country. The principal feature operating in
this connection was the gradual exhaustion of the splint coal
in many districts, and although the writer was given to
understand that supplies were ample for some time yet,
those responsible were keeping an eye on the possibility of
either supplementing or supplanting the splint coal by coke.
Several new coalfields are being opened out at the present
time, and he (Mr. Cooper) was quite sure that those who
are so extending would only be too delighted to strike a seam
of really good coking coal.

The writer had examined in the laboratory a number of
coals from various parts of Scotland, and he records in
Table I. the results of a number of tests made on these
coals. * These results indicate the amount of coke,
by-products, etc., which might reasonably be expected when
the coals were carbonised in a modern type of oven such
as he would describe at a later stage. " So far as the
by-products are concerned, the majority of Scottish coals
would yield very favourable returns indeed. Judging from
tests performed, he estimated the probable yield of coke
to be about 65 per cent.; sulphate of ammonia, 1’5 to 1’7
per cent.; tar, 4 to 6 per cent.; and crude benzol, about
3 galls, per ton of coal. These were certainly much better
yields of by-products than were obtained in many parts of
Great Britain.

Table I.—By-products Recovered from Coals from
Various Districts.

District.	Coke.	Tar.	Sulphate of ammonia.	Benzol.
	Per cent	Per cent.	Per cent.	Gallons.
Cumberland ..	....	69	..	. 5	1’5	3’0
Durham 		....	72	..	4	1’3	.	2’5
South Yorkshire 70		4’5	1’45	..	.	2’75
Staffordshire..	. ..	65	5’5	1’55	3’0
South Wales ..	....	84	1’5	..	0’9	*
Scotland		65	5’0	1’6	3’0

* Not recovered