February 19, 1915.

THE COLLIERY GUARDIAN.

385

= 120.

of extra rope must be scrapped when it reaches the age
limit prescribed by law. Mining men in this country
have not taken kindly to the proposals described, any
more than they have hastened to adopt the Koepe or
even the Whiting systems, which certainly minimise
lateral friction. The latest proposal is, as already
stated, to mount and overcoil the rope on a narrower
drum.

One wonders, however, whether the present ordinary
everyday system is really as good as it might easily be
made, even apart from any of the rather drastic innova-
tions which have been proposed. Under the present
system of parallel drums without overcoil, it would seem
that (in new plants, at any rate) there is no real
necessity that the angle A should ever exceed 1| degs.
or thereabouts, even at the deepest pits. The largest
new undertaking known to the writer is one where it is
proposed to raise 12 tons of coal per wind from a depth
of 800 yards. It may be assumed that in th'S case a
good rope of the flattened strand type and 3 in. (approxi
mately) in diameter will be sufficient to raise the load.
Taking a 30 ft. drum, the value of R would be—

t? _ D _ 30 x 12
d 3

There would then be for substitution in formula (2)
H = 800 yds., and let it be arranged that A must not
exceed 1J degs. If so, formula (2) would have to be
employed, as follows:—

T 10H 10 x 800 AA.A ,
L = AR = 120 V 11 = 444ydS ’
which is not at all an impracticable distance, whilst
11 degs. of friction angle cannot be called an exorbitant
maximum. For lesser loads and lesser depths, the
friction angle will be less. The width of each drum,
according to formula (5), will be—

W - j ® — a, + 7 X 2,400 _ , _
W ~ X + 20R “ X + 20x320 ~x + 7'

If x — 1, this will allow three spare coils on the drum,
and W = 1 + 7 = 8ft.

The destructive work done on the rope cannot be
calculated as a positive quantity, since one cannot quote
any precise value of the coefficient of friction. The
surfaces in contact are the sides of the rope, which may
be of the ordinary kind, or of the flattened-strand type,
or of the locked-coil type. The coefficient of friction,
even for the some angle of friction, will be a maximum
when the ordinary type of rope with its corrugated sides
is employed, and a minimum when a locked-coil rope
with its very much smoother sides is employed. Hence,
a most important element in the problem of lateral
friction is the type of rope employed, whether the
relative diameters for equal strength, or the relative
roughnesses of their sides be considered.

If, however, the positive quantity of destructive work
done on the rope by lateral friction cannot be stated,
the ratio in which the friction varies with the angle A is
easily determined. A simple calculation will prove that
within the limits of A = 1 and A = 3 (or even up to
A = 10) the friction practically varies as the square of
the angle, if other factors remain the same. For
example, if, with a given value of L, the rope is in
the centre line at the beginning of the wind, the
destructive work of the lateral friction will be four
times as great as it would have been if the rope had
been centred for the middle of the wind.

The foregoing results may be collected and summarised
as follows :—■

1.	Other things being equal, the lateral or side friction
will be at a minimum if the rope lie in the centre-line at
the middle point of the wind.

2.	Other things being equal, the lateral friction varies
inversely as the distance L intervening between the
pulley and the drum.

3.	Other things being equal, the lateral friction varies
inversely as the ratio R which the diameter of the drum
bears to the diameter of the rope. The magnitude of
the ratio R may be augmented, not only by increasing
the diameter of the drum, but also by decreasing the
diameter of the rope—that is, by using only the best
material, so that a smaller diameter of rope may suffice
for a given load.

4.	Other things being equal, the lateral friction varies
as the square of the angle A of friction.

5.	Other things being equal, the destructive character
of the lateral friction varies with the roughness of the
rope ; hence, ropes of the flattened-strand and locked-
coil types suffer less than ropes of the ordinary type,
because the coefficient of friction is less.

6.	It is also obvious that the lateral Fiction in any

given case will be very much less, if the rope be kept
thoroughly lubricated, than it can possibly be if this
point be even partly neglected.	y

These half-dozen bald statements probably represent
as much as most practical men have yet learned about
the subject of lateral friction, as it applies in the case
of winding ropes. It does not follow, however, that all
practical men have as yet fully appreciated what these
stale statements lead to. Therefore, the writer proposes,
at an early date, to submit another short paper, the
object being to point out, if possible, the natural
remedy.

On Thursday next at 8 p.m. at the Institution of Electrical
Engineers, Victoria Embankment, W.C., a paper on
“Electricity Applied to Mining,” will be read by Mr.
C. P. Sparks. This paper is being read at the Yorkshire
Local Section, Philosophical Hall, Leeds, on Wednesday,
February 24, at 7 p.m.; at Newcastle, at the Mining
Institute, on Monday, March 1, at 7.30 p.m.; at Birmingham,
the University, Edmund-street, on Wednesday, March 3,
at 7.30 p.m.: and at Manchester on Tuesday, March 9, at
the Engineers’ Club, 17, Albert-square, at 7.30 p.m. This
paper will also be taken after the address by Mr. D. E.
Roberts, at the South Wales Institute of Engineers, Park-
place, Cardiff, on Tuesday, February 23, at 5 p.m.

WINDING ENGINE SIGNALS.*

By Wilfrid H. Davis.

Whereas previously each district, or, indeed, each
individual colliery, was free to adopt its own code of
signals, it is now imperative upon all colliery companies
to adopt a uniform code,- as laid down by the Home
Office, and this code shall be given to the winding
engineman both in a visible and in an aural form.

The simpler and loss costly plan obviously is to
provide an indicator upon the face of which all signals
are inscribed, and over this dial a hand traverses step
by step, pointing to the nature of the signal. Such a
system has the approval of the Home Office, as comply-
ing with the rule.

An objection has been raised by managers and winding
enginemen, although approved elsewhere, that, as when

DERBY S LONDON

Fig. 1.—Lever Type of
Contact-maker.

Fig. 2.—Electric Indicator before
“ Men ” has been Signalled.

LOWER

12

RAISE.

Slower

.STEADILY.

RAISE
.STOP,

/4

5 J

10

—

9,\

k 8 a

n

Fig. 4.—General View

of Releasing Apparatus.

men are about to be raised or lowered, three rings are
to be given on the aural signal, and the indicator must
show the cautionary word “ men ”; then the executive
signal of one or two rings, which mean “ raise ” or
“ lower ” must show the words visibly on the indicator.
This involves the clearance or removal of the cautionary
signal “ men ” before the regulation can be Complied
with. Some modification of the simple dial, therefore,
becomes necessary in order to avoid what is generally
termed a “ cumulative ” signal.

The writer will endeavour to explain how to overcome
this objection; but it will be well to .state at the outset
that three varieties of systems may be employed,
namely : (a) Electrical throughout; (b) mechanical
throughout; or (c) mechanical up to the pit bank, and
therefrom converted into electrical.

Electric Signals : The Indicator.

The novelty in the apparatus illustrated by fig. 1
consists in the lever which has to be pulled forward
instead of being compressed. This is arranged to avoid

* From a paper read before the North of England Insti-
tute of Mining and Mechanical Engineers.

accidental contact by leaning on the lever, or otherwise
inadvertently making contacts. Two .such contact
makers are required for the onsetter, one (usually
painted red and preferably fixed higher) actuating the
cautionary signal “ men, ’ ’ and the other (usually painted
black or green, and preferably fixed lower) actuating the
executive signals. The essence of the indicator lies in
the operating mechanism, which consists primarily of a
plunger or straight rod of steel surrounded by an electric
solenoid, which plunger, upon being electrified, is sucked
or drawn up rapidly, and strikes a gong with a clear and
loud note. The plunger carries a pawl, which engages
in a ratchet, and on each rise of the rod carries a hand
one step over a dial. Thus it will be seen that, with a
minimum of parts, a combined bell and indicator has
been evolved which is extremely simple in construction,
and has practically nothing that can get out of order.

The dial over which the hand travels step by step
contains the nature of the signal as follows :—One
(raise or stop); two (lower); four (raise steadily); five
(lower steadily). These are the “ executive ” signals.

In order to indicate the cautionary signal “ men,” and
to avoid what is known as a “ cumulative ” signal, a.
separate plunger and solenoid are provided in the same
case, and the plunger strikes a gong which is common
to both strikers. This second plunger also carries a
pawl, which engages in a second ratchet, and on each
rise of the rod carries a flag, upon which is painted the
word “ men.” This flag travels behind the dial pre-
viously described, and at the third .stroke on the gong
appears in an open space cut in the dial. Thus the
onsetter, and, in his turn, the banksman, can signal to
the winding engineman the cautionary signal “ men,”
in addition to any of the required executive signals from
one to five. Additional spaces are contained on the face
of the dial for any number up to 12, which can be coded
and inscribed to suit special requirements. Figs. 2
and 3 show the general appearance of an indicator before
and after “ men ” has been signalled. Two indicators
are fixed in the engine house, one operated by the
onsetter, and the other by the banksman.

The re-setting of the indicators is an important, point

Fig. 3.—Electric Indicator after
“Men” has been Signalled.

LOWER

12

’RAISE:

RAISE.
toSTOP.

Slower
.STEADILY.

9\
k 8

3WEI

Z4

5 J

in connection with visual signals, and, so far, it has not
been clearly defined by the Home Office what should
effect the release or clearing of the visual system, or at
what period of the winding the signal should be cleared.
Generally it is preferred that the signals should be
cleared automatically, that is, independently of the
human element; and it would appear to be a correct
assumption that the signal “ is complied with ” when
the engine starts to move. The indicator described can
be released in various ways, but the most favoured
arrangement is for the engine to effect this auto-
matically.

The contact-making release (see fig. 4) consists mainly
of an upright shaft carrying on each side two
arms. These arms are composed of metal tubes, start-
ing and ending with non-conducting material, and
forming a grooved trough, upon which metal balls rest
and run; the upright shaft is driven through gearing
from any convenient shaft of the winding engine. A
slight movement of the engine causes a considerable
movement of the arms, and the balls travel outwards
by centrifugal force in their ball races : in so doing they
complete an electric circuit, which actuates a solenoid