October 8, 1915.

THE COLLIERY GUARDIAN.

725

Midland Institute of Mining, Civil, and Mechanical Engineers.

The members of the Midland Institute of Mining,
Civil, and Mechanical Engineers held a general meeting
at Sheffield on Saturday. Two of the papers presented
at the annual meeting of the Institution of Mining Engi-
neers at Leeds were on the agenda, and provoked good
discussions, and other items were the election of officers
for the ensuing year, the assumption of the chair by the
new president (Mr. C. C. Ellison, managing director of
the Monckton Collieries, near Barnsley), and the annual
report.

The following new members were elected :—Mr.
Clifford Palfreyman, Hermitage, Lithgow, N.S.W.,
Australia; Mr. Edward Stuart Clark, Llay Cottage, Gres-
ford, near Wrexham; Mr. Marshall Robson, Manvers
Main Colliery, Wath-on-Dearne; Mr. Thomas Brown,
mining department, the University, Leeds; Mr. Albert
Joseph Francois, 1, Imperial-crescent, Doncaster.
Associate member : Mr. Robert J. Plummer, 47, Sack-
ville-street, Barnsley. Associate : Mr. Benjamin
Hadfield, 7, Tickhill-square, Denaby Main, near
Rotherham.

The annual report of the council showed that at the
commencement of the year there were 433 names on the
register, and 16 new members had been elected, making
a total of 449. On May 31 there were only 385 fully
paid-up members, as against 412 at the corresponding
date last year. This was no doubt largely owing to the
war, and some latitude must be allowed under the cir-
cumstances as to arrears of subscriptions. The
following deaths were reported with regret :—Killed in
action—Lt.-Col. C. L. Robinson, Second-Lieut. R. N.
Carswell, Lieut. P. Brunton; from natural causes—Mr.
W. Foulston, Mr. A. T. Green, Mr. N. S. Roberts. So
far as the council were aware, they had at present 31
members of the institute serving in his Majesty’s Forces.
The balance in the bank at the commencement of the
financial year was £399 17s. 6d., and for the year just
ended £296 Os. 5d. The reason of the decrease was
the expenditure of £240 on the sections, maps, etc., and
the whole of this amount was included in this year’s
accounts. Five meetings had been held during the
year, one at Doncaster, two at Sheffield, and two at
Leeds, and eight papers had been read. The sections of
strata of the coal measures of the Yorkshire coal field,
together with cross-country section and map, were com-
pleted last October, and copies were issued free to
members and other gentlemen and firms or public
institutions who had supplied information, or were con-
sidered entitled to receive them. The cataloguing of
the library of the institute by Mr. F. Oxley was
practically completed, and was being prepared for print-
ing. The index contained approximately 7,000 entries,
which consisted of the subjects of papers and matter of
interest to mining engineers contained therein.

On the motion of Prof. O’Shea, seconded by Mr.
W. H. Chambers, an alteration was made in Rule 9 of
the institute, relating to the election of members of
the council. The old rule provided that the four
members of the council who had made the fewest
attendances should retire at the end of each year, and
should not be eligible for election again until they had
been one year out of office. Prof. O’Shea pointed out
that, owing to this, men who were very active members
of the council, but who through no fault of their own
■had been unable to attend the meetings, had had to
retire, in many cases it had taken a large number of
years to get them back. The new rule provides that
“ Councillors shall hold office for two years, and be
eligible for re-election on the expiration of their terms
of office. One half of the council shall retire annually.”

The New President.

The election of president, vice-presidents, and council
for the ensuing year resulted as under :—President, Mr.
Charles Chetwyn Ellison, managing director of the
Monckton Collieries, near Barnsley; vice-presidents,
Messrs. Thomas Beach, T. Stubbs, and E. W. Thirkell;
council, Prof. O’Shea, Messrs. James Mellors, H. F.
Smithson, W. D. Lloyd, John Gill, J. H. W. Laverick,
Thomas Gill, J. R. Wilkinson, J. E. Chambers, R.
Holiday, R. Clive, and W. Hay.

Mr. Hargreaves, in announcing that Mr. Ellison had
been unanimously elected president for the ensuing year,
and in himself vacating the chair, expressed his sincere
and hearty thanks to all connected with the institute for
the great kindness he had received at their hands during
the two years of his presidency. That remark especially
applied to Mr. Blake Walker, the secretary. He would
be a bold man who undertook the duties of president
without the certain knowledge that Mr. Walker’s good
offices would be at his service at any time. If there was
any heat and burden in connection with the management
of the institute, it all fell on Mr. Walker’s shoulders, and
the position of president was very happy and very easy.
The same observation, in less marked degree, applied
to the members of the council.

Mr. C. C. Ellison, who was received with applause,
expressed his sense of the honour that had been done
him. Fie knew that the position of president was a very
difficult one to fill satisfactorily, and he also felt that he
was following a very good president, who was very
popular amongst all the members, and who had done a
great deal for the institute. He personally did not feel
worthy to occupy the position, but he should do every-
thing he could to ensure that the business was carried
on well, and to make the meetings not only instructive,
but interesting and attractive to some of the members
who did not often attend them. He would like to ask
all those who were in charge of collieries to give their
young men and managers every facility and encourage-
ment to attend the meetings. His opinion was that a
manager ought to be able to find his four or five after-
noons during the year to attend the meetings, and if he
was not sufficiently interested to keep in touch with the
work of the institute, it was not for the good of himself
or of his concern.

Mr. W. H. Chambers proposed a vote of thanks to Mr.
Hargreaves for. his services as president, and this was
seconded and carried with heartiness.

Mr. Hargreaves briefly replied.

Compressed Air and Coal Cutting.

The first paper discussed was that by Mr. Sam Mavor
on “ Compressed Air for Coal Cutters,” which was pre-
sented at the annual meeting of the Institution of
Mining Engineers at Leeds on September 15. (Colliery
Guardian, September 17 and 24 and October 1.)

Mr. Mavor introduced the subject by calling atten-
tion to a few of the salient points. He said it seemed
to him that the use of measuring instruments—not only
pressure gauges but rate of flow meters—should be taken
up very seriously by colliery engineers and managers.
By this means they would, know what volume was
actually being delivered by the compressors, and would
not have to take the volumetric efficiency from the
makers, who did not know, except from their theoretical
calculations. The output of a compressor ought to be
measured by meter just as the output of an electrical
generator was; then they knew what they were getting
for the power they were putting in, they knew what
they were delivering to the main, and what they had a
right to expect in work done. He explained that the
paper was written rather hurriedly, and was not in fact
completed. He wished to add a section on air com-
pressors, and hoped he would still be allowed to do
so, so that it might be printed in the Transactions.
Among the representative types of meters referred to, he
was adding the standard orifice, which was one of the
most simple of all. It consisted of a diaphragm with a
standard opening, mounted between two clunches, with
connections for piping to lead to the manometer. An
instrument of that kind might be kept permanently in
the pipe, and the manometer or equivalent instrument
might be connected whenever required. The disc, of
course, was as permanent as the pipe. It did not get out
of order, and it gave at selected points the possibility of
ascertaining, by attachment of a manometer, the volume
of air passing.

Speaking of the loss of pressure in piping, Mr. Mavor
alluded to the curves shown on figs. 7 and 8 of his paper,
one of which was plotted from tests of a 3 in. pipe, and
the other from tests of a 6 in. pipe. He said the results
of the test of the 3 in. pipe conformed approximately to
the curves based on published formulae, such as Darcy’s
and Kent’s. In a later table, referring to the tests of
hose pipe, the results conformed fairly closely with the
published formulae. They were almost identical in the
case of some sizes, of 3 in. and under. But when they
came to the larger sizes of pipes, there appeared to be a
very wide discrepancy between the observed results and
the published formulae. Fragmentary although the tests
were, the very large number of observations upon which
each of the curves was plotted, and the consistency of
the observations, were strong evidence of the approximate
correctness of the curves. He had had plotted on the
same scale the curves based on published formulae. He
found that these theoretical formulae rose very much
more steeply than the test curves. The authors of them
frankly acknowledged that they were on a somewhat
narrow basis—that they were based on experiments with
air at quite low pressure, and with pipes of quite small
size, so that their numerical coefficients appeared to be
quite wrong when used in formulae applied to piping of
the sizes used in collieries, and to pressures of the order
used in collieries. He had had a new figure made to
replace fig. 7, on which these theoretical formulae would
be shown in dotted lines. The short of it was that the
tests indicated, and, as far as he was concerned, they
satisfactorily proved, that actual losses in the larger
piping were a great deal less than the published formulae
would lead them to expect, and that, he thought, was
quite consistent with the results of ordinary practice.
He had found that the losses of pressure in the main
pipes were generally very moderate indeed—in some
cases very low, and almost negligible—up to consider-
able distances in-bye. The serious losses began when
they got into the in-bye region, to branch pipes, small
valves, and hose pipes.

The President said the subject was most interesting
and important, and he was afraid Mr. Mavor’s paper
would prove their ignorance more than ever. He had
always found that the question of economy of com-
pressed air was one of the most difficult problems which
they had in the pits, especially the older pits where the
pipes had got buried.

Mr. W. D. Lloyd said Mr. Mavor’s paper would repay
the careful study of all users of compressed air. That
the pressure at which compressed air was used in coal-
cutting machines was usually very low was a fact which
was fairly well known to makers and users, as also was
the fact that there was an enormous drop in pressure
between the gate end and the machine when the latter
was running, if a trailing hose of 2 in. diameter was
used. But he thought that the main difficulty in using
compressed air economically for coal cutting was more
in the machine than in the trailing hose, the drop in
which was rather an effect than a cause. Mr. Mavor
drew attention to the high losses that there were in the
trailing hose. The cylinders of the machine must be
of ample size to exert a maximum power per stroke
when .starting up and running slow to overcome jamming
and other difficulties in cutting, but as soon as the
machine got up to speed, and was cutting normally a
much lower power per stroke, and therefore a less
volume of free air per stroke, was required. The valves
were set with a fixed cut-off, which was usually very'
near the end of the stroke. Therefore, if the air was
constantly supplied at high pressure at the stop valve,
greater power was developed than was required, and the
machine raced and caused undue strains, unless the
operator regulated the supply with the stop valve. But
with a 2 in. hose there was no need to do so, as the
supply was automatically reduced by wire drawing in
the trailing hose, although the area of the hose was
sufficient to pass the quantity required to fill the
cylinders to full pressure when starting or running slow.
For more economical working, a radical alteration was
required in the machine itself, but it was not easy to
suggest how this could be done-when compressed air
was the motive power, and the machine had to work
under the difficult conditions which obtained at the coal
face. If steam were the motive power, the desired
result might be obtained by using an automatic cut-off
on the valve gear, but there were obvious difficulties
in applying such a gear to a coal cutter driven by com-
pressed air. There was a possibility of arranging the
two cylinders so that they could both run at high
pressure when starting up, but could, by using a suit-
able controlling valve, be instantaneously changed to
run compound when the speed had been obtained. He
tried this idea a few years ago, and obtained promising
results, even when using cylinders of equal diameter,
and believed that by employing cylinders of suitable
ratios successful results would be obtained, particularly
if arrangements could be made to allow the exhaust
from the high pressure cylinders to be reheated by the
surrounding atmosphere before doing its work in the
low pressure cylinder. In the preliminary experiments
that were made there was very little tendency to freeze
up, even without any special arrangement on the com-
municating pipe between the two cylinders. More
economical working would be obtained if it were possible
(though he did not say it was) to fit coal-cutting
machines with changeable gears, so that they could start
up on a low pressure gear and switch over on to a
higher gear, always keeping the cylinders running at a
fairly low speed, independent of the speed of the cutter
wheel or cutter bar. Failing any radical alteration of
•the machines, the use of a trailing hose, say, 2| in.
diameter, as recommended by Mr. Mavor, would appear
to have an advantage. He had tried 2J in. hose, but,
for the reasons given above, he had found it unneces-
sarily large, and it was very considerably more difficult
to handle. Fig. 12 in Mr. Mavor’s paper was based on
20 yds. of hose pipe. He thought the author’s point
would have been much more borne out if he had
extended that figure to a longer length. Although Mr.
Mavor said that the majority of pipes used were only
40 yds. in length, still there were a great many longer
ones in use, and 60 yds. was quite a common length.
Mr. Mavor suggested that the insertion of iron pipes
inside the -trailing hose for making repairs was a practice
that should be avoided. What other method would
he suggest for coupling up the pipes, instead of that?
As regarded the use of meters for measuring the total
quantity of air produced, no doubt this would be
extended if users could be satisfied as to their reliability,
and that the automatic corrections for temperature and
pressure were sufficiently accurate. In this connection,
he would like to ask Mr. Mavor if the figure that he
published of his actual test from coal cutters had been
corrected for variations in pressure, and if so, how this
was done. Mr. Mavor drew attention to the waste of
power in compressing air to higher pressures for colliery
purposes. He (the speaker) thought it was a fairly
well ascertained fact that for colliery purposes a pressure
of 601b. was all that was necessary; in fact, pressures
of 50 and 55 lb. were really quite sufficient for coal
cutting and pumping, but, as Mr. Mavor pointed out,
it was essential that pipes of sufficient area should be
used. The argument to which Mr. Mavor alluded, that
higher pressures were required for some purposes, was,
he thought, rather discounted now by the fact that
hammer drills could be obtained at the present time,
which worked quite well with the lower pressures, say,
of 451b. Therefore, for colliery purposes, there was
really no advantage in running compressors up to 75 or
801b., when they were going to use the machine at
probably 201b. or less; it was simply actual loss of
power.

Mr. Walter Hargreaves expressed his thanks to
Mr. Mavor for the extremely valuable paper which he
had contributed. He had the pleasure of having Mr.
Mavor’s assistant at his firm’s collieries for the purpose
of making some of his experiments. He did not know
whether those experiments were embodied in the paper.
Mr. Mavor had been very careful not to bring forward
any names, and their thanks were due to him for having
adopted that course. But the experiments certainly
turned his thoughts into a channel into which they had