April 16, 1915.

THE COLLIERY GUARDIAN.

819

be worked to perfection in anthracite mines for a time,
when, suddenly a difficult piece of ground would stop
development work, so as to temporarily derange the
haulage system, and thus increase the cost. While
great strides had been made in mining, along the lines
of machinery'and economical systems of recovery, over
.£20,000,000 was lost annually by clinging to the use of
beehive ovens in the. Connellsville district of Penn-
sylvania.

The Friction of Winding Ropes.

Mr. FI. W. G. Halbaum wrote replying to the dis-
cussion on his paper on “ The Lateral Friction of
Winding Ropes.” He stated that the discussion had
followed almost precisely the expected lines, and
justified the statement he made towards the end of the
paper, viz., that although most practical men were fully
familiar with all the admittedly dry, colourless, and
stale data enumerated therein, it was, nevertheless,
possible that many did not realise to what conclusions
a thoughtful consideration of these data led. He had
been “ pulled up ” for adopting, even for merely illus-
trative purposes, a nominal safety factor of 10 for the
winding rope. If, however, his critics referred to Mr.
Westgarth’s table of particulars obtained from 13
collieries, they would see that the average factor of
practice was actually greater than 10. In only one
instance was the value much less than 10, and in that
instance the life of the winding rope ended in six
months. He had also been attacked—again in connec-
tion with a non-commital illustration—for making the
drum diameter 120 times greater than the rope diameter.
He felt gratified that he had forestalled those criticisms
by having submitted his promised supplementary paper
to the council of the institute. It would be seen in
that paper what his actual views were. Again referring,
however, to Mr. Westgarth’s table, it would be noted
that, in every instance where the “ yard tons per rope ”
were most satisfactory, the ratio of drum diameter was
greater than the figure employed in the paper. The
time had arrived to re-open the old question whether
the wide parallel drum should not be superseded by the
adoption either of an endless rope system of winding,
such as the Koepe, or, preferably, the Whiting system,
or by a plain, ungrooved tapered drum employed in con-
junction with simultaneous decking and the abolition
of the old-fashioned keps system. Whichever of these
alternatives were adopted, the following results would
accrue, basing one’s figures on the example of a 12-ton
load of coal from a depth of 800 yds. :—(1) The complete
abolition of lateral friction; (2) the reduction of the
present rope cost by at least one-half; (3) longer life of
the rope, owing to less frequent renewals, following on
the abolition of lateral friction; (4) reduction of drum
diameters by some 40 per cent.; (5) a corresponding
reduction in the .dimensions of the engines; and (6) a
substantial increase in the actual (as opposed to the
nominal) factor of safety. He was acquainted with one
case in which the management was already taking sub-
stantial steps in the direction indicated, and he predicted
with some confidence that the success finally attained
would be commensurate with the enterprise manifested.

Overwinding and Overspeeding.

Mr. Poole then read his paper on “ The Prevention
of Overwinding and Overspeeding in Shafts,” which
appears on p. 805.

Moving a vote of thanks to Mr. Poole, the President
said the subject was a very important one, and one
which had been forced upon the mining community by
the Government. He thought that several of the
appliances in operation in that district were not only
overwinding preventers, but overspeeding preventers
also, and it was quite obvious that the two should be
combined.

The vote of thanks was cordially given.

Mr. J. S. Barnes (Lincoln) wrote stating that,
although Mr. Poole’s paper was admirable as far as it
went, it did not go far enough or deep enough, nor did
the whole conclusions hold good. Mr. Poole stated “ the
overwinder should be set to work between the two fixed
points, namely, the top and bottom of the pit, and, for
any movement of the cages beyond those points, it
should act immediately.” First, taking as an example
the decking and raising of the cage from the keps or
fallers and its displacement thereon, that was a case in
which the engineman had to reverse his engines. Unless
automatic keps were adopted, in which case there was
no need to raise the cage in order to release the keps or
fallers, there was a liability of the engineman during
reversal of the engines to overwind whilst raising the
cage from the keps or fallers, and especially so in the
case of very large engines and deep shafts and high-
pressure steam. The remedy would be to deck either by
hydraulic or stage decking, with automatic keps or
fallers, so that, when once the cage reached the pit bank,
the engine would have to be reversed, so as to put the
cage on to the keps or fallers. That position of the
reversal was equivalent to commencing winding again,
and for the cage to go down the pit, and that reduced to
a minimum the possibility of overwinding owing to the
winding engineman starting the engines in the wrong
direction. Secondly, taking as a further example the
case where long timber, girders, or a horse-box had to
be sent down the mine, and the cage had to be raised
above the banking level in order to sling such material
beneath the cage, the case set out by the author did not
meet that condition. Thirdly, assuming that, the sump
or dip at the pit bottom had to be cleaned out, the
engines at the top and bottom should be provided with
overwinding gear to allow for these ’ operations.
Fourthly, in the case of shafts where several seams
were worked continuously, but where the winding was
intermittent and alternately from different seams,

when winding from any seam above the lowest or
deepest, it was obvious that the cage, when going to an
intermediate seam, would stop there, to be loaded and
unloaded whilst the other cage was somewhere at
another point in the shaft. There was, in that case,
the possibility of the engineman running his engines in
such a direction, through a mistake in reversing the
engines, as would cause one cage to overwind and the
other to dash into the sump beams or pit bottom.
These conditions were not met by the author.

Mr. Poole’s formulee for velocity, acceleration, time
and space, owing to steam compression, cut-off, fluctua-
tion of speed and load, were not correct or applicable
to practical working. It was not wise to take the
26,0431b. of frictional force mentioned by the author,
as the engine brakes must be of sufficient sectional
area, and of suitable material to allow of the engines
being stopped not only with a full unbalanced ordinary
load, but with the probable heaviest unbalanced load of
girders, bricks, etc., going down the pit. Allowance
should also be made for steam- leaking past the throttle
valve into the engine cylinder, but, where there was a
good engineman, he could, of course, save the brakes to
a tremendous extent by manipulating his reversing
lever so that he could control the engine. In fact, that
was often done, and, if the engines attempted to race
away beyond ordinary working speed, it was usual and
customary for the engineman gradually to notch up his
reversing lever so as to get nearly or actually into the
central neutral point, and so lock steam in the engine
cylinder to act as a buffer. This was due to the engine
cylinder ports being covered over with the valve, and
the engine could thus actually be brought to a standstill
thereby. The formula 5^-— =	ft. lb. was

2 g 64’4

not correct, not only from what had already been stated
relating to the formulae, but because part of this energy
was due to the live loads ascending and descending the
shaft counteracting one another, and, therefore, having
to be deducted accordingly. There was no statement
by the author as to momentum and inertia and to shock
causing extra stress at the commencement of a wind.
Hence, it was generally preferable not to attach much
importance to such diagrams, formulae, and calculations
as the author had put forward as a solution to over-
winding and overspeeding-problems, because, in modern
practice, the factors varied constantly from wind to
wind or from hour to hour daily. As to the author’s
remarks respecting speed, it was usual and essential
always for the engineman to start his engines very
steadily at a low speed, and gradually to increase the
speed without jerks or shock, and, in deep mines, to
run the cages a certain distance without admitting a
greater amount of steam, and then gradually shut off
the steam so as to bring the cages slowly to rest. If
these conditions were departed from, whether the engine
was fitted with overwinding gear or not, accidents would
occur sooner or later. The question whether overwind-
ing gears should operate on the main throttle valve or
on an independent valve should depend upon circum-
stances, make of overwinding gear, etc. The author
had omitted to mention electrical winding and its over-
winding proposition. Many instances occurred where
the winding engineman threw on full speed so as to raise
the full loaded cage from the pit bottom, and, owing
to the steam pressure being under the ordin ary working
pressure, or if the full load, if pit roof or holing dirt,
was much heavier than coal, he was often obliged to
let the cage down again, many times at a very high
velocity, and the cage at the pit bank came up at a
high velocity. That aspect required consideration.
Nothing was said by the author regarding the use of
balance ropes, which put his deductions re formulae,
velocities, loads, acceleration, retardation, etc., out of
rational and practical application.

Mr. H. W. G. Halbaum (Cardiff) wrote congratulating
the author on his courage in tackling a subject the
fascinations of which were only exceeded by its diffi-
culties. The writer thoroughly agreed that speed-
controlling gear should be operative throughout the
wind, but was unable to agree with the author as to the
brake force required in .the event of the speed-control
gear failing to act. It was as possible and as great an
evil to have too much brake force of the automatic kind
as too little. In no case should the automatically
acting brake force be so great as to be able to arrest
the rotation of the drum before the ascending cage had
had time to exhaust its kinetic energy. The gear
should be so designed that it could be depended on to
bring the machinery to rest within a distance not
greater than 40 ft. or less than 31-J-ft. It should be
noted, however, that although such perfectly designed
automatic gear might, and probably would, be most
faithful to its trust, it was obviously quite destitute of
the human element or discrimination. This rigidity of
action in the gear should be, as far as possible, dupli-
cated in the rigidity of conditions under which such
action might take place. He did not gather what the
author meant by the “ frictional force.” Lid he mean
the gross force applied to the brake, or did he mean the
net effective force applied by the brake and transmitted
to the drum oppositely to the line.of its rotation? He
suggested that, apart altogether from friction, the
system contained other retardative forces than those
represented by the brakes. For example, if the ascend-
ing cage passed the banking level at a speed of 45 ft.
per second, the descending cage, at the same instant
and with the same speed, would strike the pit bottom.
It was clear that if the landing place was practically
solid, the .kinetic energy of the descending cage extin-
guished itself automatically. Hence, five tons of cage,
tubs, and chains at once fell outside any system of
brakes. The case of the ascending cage was more
interesting. A velocity of 45 ft. per second in the
kinetic energy corresponded with a height of 31-444 ft.

in its potential equivalent. Hence, left to itself, the
ascending cage would; have no kinetic energy left at a
height of 31-444 ft. above the banking level. Not only
so, for the allowable height was 40 ft., and obviously
the unbalanced load could negotiate the remaining 8| ft.
of the distance only by absorbing energy from the rest
of the system. He calculated that some 846,000 ft.-lb.
of the kinetic energy would be absorbed in the manner
described, to say nothing at all of the additional absorp-
tion effected by the friction of the moving parts. The
brake power in that not unlikely case would be 21,600 lb.,
as against 42,7501b. estimated by the author. If,
however, in the case just illustrated, the 42,7501b. of
effective brake force were actually provided, and came
into action, the drum would be stopped in less than
three-fifths of a revolution, after which the ascending
cage, by virtue of its kinetic energy alone, would con-
tinue its upward course, against the slack rope, for 11 ft.
more, and then drop back through the same distance
before the rope again became taut. The possible
consequences could only be imagined.

Mr. A. Hanley (Bristol) remarked that the author had
spoken of ” absolute safety and reliability.” It seemed
time that the use of the word “ absolute,” as applied to
mechanism with many separately acting parts, each of
.which was subject to wear and tear, was discontinued.
After some detailed criticism of Mr. Poole’s conclu-
sions, Mr. Hanley went on to say that winding opera-
tions were too serious for tricky little toys and formulae.
A winding controller was an appliance built to suit
particular conditions, had small limits of variation, and,
by its nature and duty, would probably always remain
the most troublesome machine at a pit. Its faults and
deficiencies should be cured, and that might not be a
difficult matter for makers if they were fully informed as
to the facts. Although Mr. Poole made out no case for
the necessity of a sub-controller, no case would be neces-
sary if he knew of, or had, an appliance which cut out
a risk which controllers left or failed to deal with.

Mr. A. W. Brown (Manchester) said a properly
designed and fitted overspeed and overwind device would
prevent sudden excess strains coming on the winding
drum and ropes through the sudden application of the
full braking force. The brakes themselves should be
strong enough to withstand the strain of a sudden appli-
cation, but the heat generated gave rise to difficulties
which were doubtless appreciated and catered for by the
makers of winders. It was easy to construct a device
which would conform to the curve during the full-speed
portion of the wind, but difficulties arose in the acceler-
ating and decelerating portions, especially at low speeds.
At low speeds the governor employed in the mechanical
devices was imperative, unless made out of proportion
to the work to be done, and the stepped profile used in
most of the mechanical devices employed with steam,,
and many alternating current rheostatically controlled
winders, also introduced errors which were reduced by
increasing the number of steps. He could heartily
endorse Mr. Poole’s desire for a device which would
merely reduce the speed to the normal value in case
of an overspeed, instead of stopping the winder, but he
was not aware of such a device.

Mr. A. Du Pasquier (Manchester) remarked that Mr.
Poole had dealt only with steam-driven winding engines,
but, as the possibility of economically securing a flat-
topped speed cycle, as shown by Mr. Poole, with the
resulting lower maximum velocity, was one of the many
advantages of the electrical winding engine, it might be
in order to discuss briefly the means available for pre-
venting the cage from coming to bank at excessive
speed with electrically operated engines? With the
Ward-Leonard control, one could say that accidental
overwinding was impossible. It had been necessary to
devise means whereby the control of the three-phase
winding engine might be rendered equally safe in that
important detail, viz., excess speed when approaching
bank. All such devices (most of them mechanical)
relied in principle on automatically shutting off the
power and applying the brakes at the required point in
the shaft, should the driver fail to do so. It should be
noted that power was not shut off gradually, as with the
Ward-Leonard system, the essential difference being
that with the latter the gradual shutting off of the power
was a natural part of the operation of each wind,
whereas with the three-phlase engine, or with the steam
winder, it was rather to be regarded as an emergency
application, and, as such, there were certain advantages
in emphasising that fact on the driver’s mind, by making
him have to re-set the trips after a miswind of that
nature. Such a device, in order to give adequate pro-
tection, must be of the true profile type, at all events as
regarded the maximum velocity and retarding periods
of the wind. Ordinary excess speed devices, consisting
of one centrifugal trip which had to be set somewhere
in excess of the normal maximum velocity, gave no
protection during the critical period, although that was
apparently not generally . appreciated. With a three-
phase winding engine, it was not necessary to control
the speed during the accelerating period, as the
maximum velocity was fixed by the frequency of the
supply, and the rate of acceleration was either naturally
automatically controlled, or, where in smaller winding
engines other types of controllers were used, .thereby
unduly decreasing the starting time, would, at the worst,
only result in tripping the circuit breaker. For the
same reason, viz., that maximum velocity by the:
frequency of the supply, it was not necessary to control
the speed during the normal maximum velocity period
of the wind; but that feature should always be embodied
so as to ensure protection against the possibility of
excess speeds arising, if lowering unbalanced. The
critical period was the retarding period, and there the