WIRE ROPE--THE GIANT
"Pig" and "ore" and melting materials, with a condiment of carbon, are
the body and bones of steel wire. Their virtues, combined and
intensified by tireless processes, and tested unsparingly at every
stage, are united in wire rope; and wire rope, when all is said and
done, is the mighty backbone of the wire industry.
Wire rope to the multitude is simply wire rope. But one rope is no more
like another than Jones is like Brown or Smith like Robinson. Wire rope
is a combination of twisted wires, just as men are bipeds. That is
where the similarity ends. In outward appearance as well as inward
character, habit, tendencies and behavior in emergencies, wire ropes
differ as widely as do people, and each has a meaning of its own.
Each also is the fruit of long study and repeated test of the work it
is to do not alone on machines and in the laboratory, but under actual
conditions of operation. The wire rope engineer will tell you every
rope has temperament. He spends his life knowing other people's
business--rope business--and working out their rope problems. The
answers to these problems are the four hundred different sizes and
kinds of rope that the Roebling Company manufactures on its regular
schedules. The rest are specials. Go where you will in the world
nowadays, you will find wire rope doing the work.
[Sidenote: WIRE ROPE PROBLEMS AND THE ENGINEERING DEPARTMENT]
With the completion of the Williamsburg Bridge, the Roebling Company
withdrew from competitive fields of contract engineering, but it
maintains a large engineering department and is ceaselessly busy with
construction and installation problems from all over the world. In its
files there is exhaustive record of every contract of magnitude, for
construction, haulage, mine work, ship work--for any sort of work where
rope is used and where the problems are difficult. Roebling engineers
are always on the go, studying conditions where rope is to be used, to
prescribe the fabric that will meet the need.
[Illustration: THE AEROPLANE--A WIRE ROPE CREATION]
There is, to begin with, a questionnaire of ninety-three questions, to
be filled out by the master mechanic or engineer on any special work
for which rope is to be recommended and manufactured. When these are
answered the engineer is ready to begin work, which starts with the
selection of materials and does not end till the man who is to use it
has had specific instruction as to its peculiarities and care and
protection.
For this service the Roebling Company maintains a large corps of
specialized engineers busily engaged solving the problems of wire rope
usage, and making suggestions to effect economies in wire rope
operation.
In fact, it doesn't end there. It is a saying in the Roebling
establishment that a rope is never sold until it's worn out.
[Sidenote: THE "LAY" OF THE ROPE]
The cut ends of a diversified lot of wire ropes resemble, more than
anything else, the eccentric forms of snow flakes, in their regularity
and the grouping of their parts around a center. But there is nothing
haphazard about the formations. Even the core is figured in the number
of days it will add to the rope's life under varying conditions. The
wide difference in ropes consists not only in the materials employed,
which have much to do with their resistance to divers strains and the
manner of their use, but in skillful selection of sizes in the wire and
arrangement in the strands of which they are composed; again in the
distribution in the strands, the twists of the strands themselves and
the "lay" or manner in which these are twisted to make the rope. It is
all the result of careful calculation.
[Sidenote: THE CORE]
A paramount factor too is the core, in securing the maximum of wear.
Its mission, in most ropes, is not to add strength, but pliability, and
to serve as a cushion to absorb the impact which the strands make under
the tension of service. The fibre cores, for this reason, are usually
treated with some lubricant. In the majority of ropes hemp is used for
a core but in those intended for stationary service the core may be of
steel. This will add from seven to ten per cent to strength and very
largely to rigidity.
When we speak of wire rope most of us have a mental picture of a round
fabric, but there are flat ropes as well, for use in mines or quarries
where the haul is from great depths and twisting is to be avoided.
These are made in all widths and thicknesses, and are constructed by
placing several strands together, side by side, and sewing them
together with soft iron wire. But it is the round rope that supplies
the great demand.
[Sidenote: THE STRAND]
In considering rope, one may start with the strand. Strands, as may be
seen from the pictures of transverse sections of ropes, vary infinitely
in character, but always with a purpose. They are made up in ordinary
practice, of four, seven, twelve, nineteen or thirty-seven wires,
according to the work the rope is meant to do. In the rope mills you
come upon long, low "stranding machines," reaching down a long room and
carrying in horizontal arrangement, wide apart but in circular
formation, the wires that are to form the strand. At a point carefully
determined with reference to the strain on each wire, in order to
preserve uniformity, all these wires come together and pass through one
opening in a twisting machine which whirls them into a unit. The
finished strand is wound on bobbins.
The direction of the twist, whether to right or left, is of moment in
determining the character of the finished product.
[Sidenote: "STANDARD" OR GENERAL PURPOSE ROPE]
"Standard rope," so called, the general purpose rope, is composed of
six wire strands and a hemp core, all being practically of the same
size; but to secure particular results the number of strands may be
four, five, eight, twelve or whatever may be desired. Already it will
be apparent that there is wide latitude in rope making for the exercise
of skill and the utilization of experimental record. This freedom in
selection and adjustment extends through almost every process. For
example, in the twists: when wires in the strands and strands in the
rope are twisted in the same direction, which ordinarily they are not,
the rope has what is known as a "Lang lay," after a rope man who
devised the system. The twist, whether in strand or rope, has distinct
effect in service. It may be long or short. If it is long the rope will
be stronger and more rigid, if short, it will gain in flexibility. When
it comes to the short twist rope, one sees the particular value of the
twisting tests which were applied and recorded away back in the wire
stage.
[Sidenote: TESTING THE ROPE]
It is singular, but it is true, that the aggregate strength of all the
wires that go to make up a rope cannot be retained in the rope, at
least in the laboratory on the testing machines. When the rope is
tested for breaking strength it is found that no sample will show more
than ninety per cent of the total, and the average is about eighty-two.
Part of this failure is due to the angle of wires in the strand, with a
resultant stress on wires in excess of applied load; therefore, the
greater the number of wires in the rope, the lower the efficiency. The
other reason is that the contiguous strands in the rope nick each other
under high tension, and so are weakened. This, however, may not be
important in ordinary working loads under service conditions. These
casual truths show with what multiplicity of tendencies the rope maker
has to deal in devising a product to give service and safety in the
often ticklish jobs it has to do, with great weights in hand, and human
lives at stake.
[Illustration: THE STEAM SHOVEL SHOVELS BY MEANS OF A WIRE ROPE]
From molecular condition, as revealed by the microscope, down to the
last petty detail in the plan of construction, there is never an end to
the problems, and gravity has to be figured into the lifetime of a rope
as surely as the elusive trace of sulphuric and muriatic acid producing
hydrogen occlusion. Wire rope is a business of exactitude and eternal
vigilance. You have to deal with breaking strengths of from 40,000 to
340,000 pounds to the square inch of transverse section, but the wire
that will lift weights at the rate of more than a hundred tons has
entirely different characteristics than the lower strength material.
And the why of that must be traced back to the treatment of the steel
when it was passing through the wire stage. Rope makers dealt with
molecules once and thought they were taking pains. They found they had
to go back to atoms to handle their problems. Today the secret seems to
lurk in the electron.
[Sidenote: FITTING THE ROPE TO ITS WORK]
Of the tricks in making ropes, there is no end. They are fitted for
their work like a soldier or a gymnast, and built for it. A tiller rope
must be flexible to the last degree, but it must be strong enough so it
will stand up under the swift tensions of a storm or in the lightning
manoeuvers of a race. Therefore, like a few ropes built for other
purposes, the composite parts are not mere strands of wire, but little
ropes in themselves, complete in all parts. And again, while ropes
exposed to weather and stationary, like ships' standing riggings, are
galvanized, those that are subjected to constant bending are not. For
every variation, there's a reason.
To the average man or woman, the elevators in tall buildings suggest
danger. The rope engineer counts them highly safe because each elevator
is equipped with a multiplicity of ropes and safety devices. What taxes
his conscience and spurs him to the last possible effort, is the rope
that goes to the "deep shaft" service, where the lives of men going up
and down in five thousand feet or more of subterranean darkness, hang
on the accuracy of his calculation.
Only now, the Roebling engineers will tell you, is wire rope being
perfected. Much of it is in what seem to be small details of
construction, which nevertheless go down into the basic principles that
make for efficiency. Rope making has been treated as an exact science,
because it dealt with materials that were more or less standardized.
They are learning now that rope has a large unknown quantity that
defies formula past a certain point. For the lack of a better term,
they call it "personality." The labor of today, and many years to come,
is to identify these intangible factors and bring them where they can
be computed to the end of securing greater endurance and safety.
In the Roebling shops there are men working who got their jobs almost
by heredity. Their fathers and grandfathers worked for John A. Roebling.
"You ask them," said the Chief Engineer, "why they do a thing a certain
way. They tell you simply that 'that's the way to do it.'" In the old
days John A. Roebling figured out the way, and gave it to his workmen
in the shape of orders--today somewhat different methods are utilized.
To the cumulative experience of over eighty years of wire-rope making,
the Roeblings have always availed themselves of the latest engineering
skill. With up-to-date research, chemical and metallurgical
laboratories, every progress in the art has been incorporated in their
product.
[Sidenote: FOLLOWING THE ROPE AND ITS USES]
The Roebling people say that wire rope is their "baby." They give it
the utmost of skill and care and caution in the making, and then to see
that these are not wasted, they follow it into the field, where it is
to serve, with personal attention to its installation and with the most
detailed instruction for its protection and use, figuring out with
nicety the speeds to be maintained, the size of the sheaves or drums
around which it should travel to minimize the strain, prescribing its
lubrication, providing printed warnings against all forms of misuse or
neglect, with pictures to show the reason why, and other instructions
and pictures to aid in detection of the first signs of trouble or
exhaustion, and the reasons therefor. Study of the Roebling method,
from the ore yard to the field of operation, makes clear the reason why
Roebling rope, from the very beginning of the manufacture, has been
accounted standard for quality.
A Roebling catalogue is never complete. It cannot list and illustrate,
without competing in size with the unabridged, more than a small part
of the uses for which rope--and much of it special rope--is made, or
the infinite number of attachments and accessories provided for
installation and use on the job.
[Sidenote: WIRE ROPE AND ITS WORK]
There is the transmission of power by means of a round, endless rope,
running at high velocity over a series of sheaves or pulleys, carrying
power to a distance of three miles; there is underground haulage, for
which five distinct types of rope are used, enabling the engineer to
make light of grades, even with staggering loads; logging, in which, in
the primeval forests of the Northwest, the horse or ox is a pigmy, and
where the giant trunks, seven, eight or nine feet in diameter, are
whisked up at the sides of mountains, hoisted into the air and
deposited on cars, to be run down to the rivers on steep inclines,
again operated by rope of great size and strength. There is quarrying,
where rope is used in quantity for guying, and for hoisting the blocks
of stone out of their beds, and then on aerial cable ways, to carry
them on high over long distances to be loaded; there are the oil
fields, in which just now, in the mad search for petroleum to supply
the world's shortage, interminable miles of wire rope are being used,
some of it an inch thick or over, to carry the drills, or for casing
and sand lines. There is shipping--the battleship and the merchantman
and the liner; the yacht, the riverman and the tug--all strung with
wire rope from stem to stern, and some of them from truck to keel as
well--not to mention mooring lines which have their own plan and
formula; there is towing, to which wire rope brought new possibilities
and freedom from old troubles and old perils--witness the towing of the
dry dock "Dewey" from Chesapeake Bay to the Philippines, thirteen
thousand miles, on a pair of 1200 foot Roebling hawsers, which stuck to
their jobs without interruption, through all sorts of weather, and
lugged their burden into the harbor of Olongapo without a sign of
weakness or exhaustion; there is dredging, for which wire rope has
largely supplanted the old and cumbrous chain which was never any
stronger than its weakest link. There is hardly an important harbor in
the world today where these stout ropes are not busy clearing pathway
and anchorage for marine commerce.
[Sidenote: MORE USES OF WIRE ROPE]
The list does not end. There are incline railways, in the mountains of
East and West alike, as well as in foreign countries, which have made
mountain climbing a primitive form of sport, and enabled one-legged men
with perfect ease to get the view from towering peaks which otherwise
would have been accessible only to the hardy mountain climber; there
are cable railways with which engineers have been able to run cars out
on an aerial roadbed of wire, over impassable gorges and morasses, to
make fills for railway or other construction; cableways, the forms and
uses of which, in transferring materials, are without number; tramways
and traction systems, which have now, save in particular instances,
given way to trolley, and the copper wire for this, again, comes in
large and continuous tonnage from the Roebling mills; there is the
perfect litter of hoisting slings, all over creation, for wherever men
are doing work or business of any kind, there is a load to lift, and
the wire rope, with its special appliances for quick hitch and release,
is fast relegating the old time chain to the category of antiquities.
In 1862 the first of elevator ropes was made. Today millions are in use.
* * * * *
It is a long story, and one variety of rope is never just like another,
save for the general purpose product before referred to, which figures
in the schedules as "Standard." But in the making of all the many
hundred kinds, the process, to outward appearance, is the same, and
impressive in the simplicity to which it has been reduced. From the
tiny specimen, made for some finical scientific experiment, to the
three-inch monster that contains single wires nearly a quarter of an
inch in diameter, and drags half a million pounds of ore, with the aid
of powerful machinery, at the Spanish American Iron Company's mines in
Cuba, the general principle of manufacture and the mechanism used in
the making are all alike.
[Sidenote: ROPE-MAKING MACHINES]
In the several rope mills of the Roebling works are a large number of
machines, some of which, built by John A. Roebling in the early days of
his rope making, are still turning out rope, and good rope. His first
product was made by hand in the old "rope walk" way. Today the ground
where he did it is covered with buildings full of speeding machinery
that has little rest--devices that stand in long rows, eating up the
strand that unwinds from the whirling bobbins to feed it, and turning
off steadily the completed rope, which passes to spools, large or
small, in proportion to its weight and size.
Simply described, the rope machine pictures itself as a hollow column
cylinder, strongly framed and braced steel from the base of which arms
extend, like the lower branches of a spruce tree. At the ends of these
the bobbins are rigged, carrying the strands which are to be twisted
into rope. These are led from the bobbins in toward the center, and
pass into the column, which carries also the core and which in its
turning twists the strands together. The complete rope passes out over
a pulley on to the spools. Machines for the smaller sizes of rope are
strung out in a long file. The larger ones require elbow room; each of
those for the making of the largest rope has a room to itself and is
installed on a foundation of steel and concrete.
[Illustration: HOISTING A HUGE NAVAL GUN WITH WIRE ROPE SLING]
When the mechanism is at work it suggests somehow the solar rotations.
The bobbins have a triple motion. On the ends of the arms to which they
are attached they travel around the column, at a rate of speed which of
course is determined by the "lay" required, but they are unwinding as
the strand pays out and also turn completely end for end, at
predetermined intervals. In the more modern machines there are two sets
of arms or "branches" above the first, for the purpose of carrying a
greater number of strands. In this type the arms carrying the bobbins
are somewhat shorter, allowing for a great rate of speed. There is
something mysterious in the sight of these flying reels of steel, or
copper maybe, for many ropes of substantial size are made of copper for
marine use, whizzing round and round like indefatigable moths around a
big steel candle, or a dervish round his own spinal column on a spot of
ground the size of a dinner plate, and the rope, hard, shining, round,
packed around its core of hemp or steel, noiselessly gathering all this
strength and energy into itself for use in the days of need. When you
see it on the spool at the side, shining with its coating of lubricant,
ready for work and able to do it, it is a little hard to associate so
respectable and dignified a fabric with the rusty heap of iron that lay
in the Kinkora yard.
[Sidenote: SPECIAL CONSTRUCTION]
There are records in the Roebling offices that tell interesting tales
of special constructions, and pictures of enormous spools of rope,
thousands of feet, in big diameters, running from spool to spool and
since one spool is an ample carload, from one flat car to another, when
loaded for shipment. Such were the huge street railway cables, made for
Australia, for Kansas City, for Chicago and New York. There is an
amusing story of the New York street railway engineer who insisted that
the cable be made in one section, 33,000 feet in length, but who
changed his mind about the beauty of it when he got the goods and saw
the elephantine spools of packed metal caving in the manholes in the
city streets on their way to the point of installation. A gigantic rope
machine was built in the Roebling plant to twist this mammoth.
The cars that carry these heavy cables were made specially for the
purpose. An ordinary car would crumble under the load, but the machine
and the cars are still in use, and busy.
When cables for street railways were discarded in favor of trolley,
wire rope men thought the day of doom had come, but the field for wire
rope for other uses has widened so fast and so far, in a rapidly
widening world, that the cable orders, big as they were, have never
been missed. It furnishes a significant index of the growth in all
industrial activity, for there is no new phase of development or
manufacture or work of any kind in which wire rope, or wire in some
form or other, does not play an indispensable part.
[Sidenote: POWER IN THE ROEBLING PLANTS]
In the three Roebling plants there are four electric power stations,
aggregating over 16,000 horse-power, and more than 150 boilers with
25,000 horse-power. The coal consumption on the three plants is
approximately 1000 tons a day, and the fuel oil consumption about
20,000,000 gallons per year. In the Kinkora plant at Roebling there are
thirteen miles of standard gauge railroad track.