Chapter 17: Mechanical Transporters and Conveyers

MECHANICAL CONVEYERS--ROPEWAYS--CABLEWAYS--TELPHERAGE--COALING WARSHIPS AT SEA

A man carrying a sack of coal over a plank laid from the wharf to the ship’s side, a bricklayer’s labourer moving slowly up a ladder with his hod of mortar--these illustrate the most primitive methods of shifting material from one spot to another. When the wheelbarrow is used in the one case, and a rope and pulley in the other, an advance has been made, but the effort is still great in proportion to the work accomplished; and were such processes universal in the great industries connected with mining and manufacture, the labour bill would be ruinous.

The development of methods of transportation has gone on simultaneously with the improvement of machinery of all kinds. To be successful, an industry must be conducted economically throughout. Thus, to follow the history of wheat from the time that it is selected for sowing till it forms a loaf, we see it mechanically placed in the ground, mechanically reaped, threshed, and dressed, mechanically hauled to the elevator, mechanically transferred to the bins of the same, mechanically shot into trucks or a ship, mechanically raised into a flour-mill, where it is cleaned, ground, weighed, packed, and trucked by machinery, mechanically mixed with yeast and baked, and possibly distributed by mechanically operated vehicles. As a result we get a 2-lb. loaf for less than three-pence. Anyone who thinks that the price is regulated merely by the amount of wheat grown is greatly mistaken, for the cheapness of handling and transportation conduces at least equally to the cheapness of the finished article.

The same may be said of the metal articles with which every house is furnished. A fender would be dearer than it is were not the iron ore cheaply transported from mine to rail, from rail to the smelting furnace, from the ground to the top of the furnace. In short, to whatever industry we look, in which large quantities of raw or finished material have to be moved, stored, and distributed, the mechanical conveyer has supplanted human labour to such an extent that in lack of such devices we can scarcely conceive how the industry could be conducted without either proving ruinous to the people who control it or enhancing prices enormously.

The types of elevators and conveyers now commonly used in all parts of the world are so numerous that in the following pages only some selected examples can be treated.

Speaking broadly, the mechanical transporter can be classified under two main heads--(1) those which handle materials continuously, as in the case of belt conveyers, pneumatic grain dischargers, etc.; and (2) those which work intermittently, such as the telpher, which carries skips on an aerial ropeway. The first class are most useful for short distances; the latter for longer distances, or where the conditions are such that the material must be transported in large masses at a time by powerful grabs.

Some transporters work only in a vertical direction; others only horizontally; while a third large section combine the two movements. Again, while some are mere conveyers of material shot into or attached to them, others scoop up their loads as they move. The distinctions in detail are numerous, and will be brought out in the chapters devoted to the various types.

MECHANICAL CONVEYERS

We have already noticed band conveyers in connection with the transportation of grain. They are also used for handling coal, coke, diamond “dirt,” gold ore, and other minerals, and for moving filled sacks. The belts are sometimes made of rubber or of balata faced with rubber on the upper surface, which has to stand most of the wear and tear--sometimes of metal plates joined together by hinges at the ends.

A modification of the belt is the continuous trough, with sloping or vertical sides. This is built of open-ended sections jointed so that they may pass round the terminal rollers. While travelling in a straight line the sides of the sections touch, preventing any escape of the material carried, but at the rollers the ends open in a V-shape.

Another form of conveyer has a stationary trough through which the substance to be handled is pulled along by plates attached to cables or endless chains running on rollers. Or the moving agency may be plates dragged backwards and forwards periodically, the plates hanging in one direction only, like flap valves, so as to pass over the material during the backward stroke, and bite it during the forward stroke. The vibrating conveyer is a trough which moves bodily backwards and forwards on hinged supports, the oscillation gradually shaking its contents along. As no dragging or pushing plates are here needed, this form of conveyer is very suitable for materials which are liable to be injured by rough treatment.

ROPEWAYS

A certain person on asking what was the distance from X to Y, received the reply, “It is ten miles as the crow flies.” The country being mountainous, the answer did not satisfy him, and he said, “Oh! but you see, I am not a crow.” Engineers laying out a railway can sympathise with this gentleman, for they know from sad experience that places only a few miles apart in a straight line often require a track many miles long to connect them if gradients are to be kept moderate.

Now a locomotive, a railway carriage, or a goods truck is very heavy, and must run on the firm bosom of Mother Earth. But for comparatively light bodies a path may be made which much more nearly resembles the proverbial flight of the crow, or, as our American cousins would say, a bee-line. If you have travelled in Norway and Switzerland you probably have noticed here and there steel wire ropes spanning a torrent or hanging across a narrow valley. Over these ropes the peasants shoot their hay crops or wood faggots from the mountain-side to their homes, or to a point near a road where the material can be transferred to carts. Adventurous folk even dare to entrust their own bodies to the seemingly frail steel thread, using a brake to control the velocity of the descent.

The history of the modern ropeway and cableway dates from the ‘thirties, when the invention of wire rope supplied a flexible carrying agent of great strength in proportion to its weight, and of sufficient hardness to resist much wear and tear, and too inelastic to stretch under repeated stresses. To prevent confusion, we may at once state that a ropeway is an aerial track used only for the conveyance of material; whereas a cableway hoists as well as conveys. A further distinction--though it does not hold good in all cases--may be seen in the fact that, while cableways are of a single span, ropeways are carried for distances ranging up to twenty miles over towers or poles placed at convenient intervals.

Ropeways fall into two main classes: first, those in which the rope supporting the weight of the thing carried moves; secondly, those in which the carrier rope is stationary, and the skips, or tubs, etc., are dragged along it by a second rope. The moving rope system is best adapted for light loads, not exceeding six hundredweight or so; but over the second class bodies scaling five or six tons have often been moved. In both systems the line may be single or double, according to the amount of traffic which it has to accommodate. The chief advantage of the double ropeway is that it permits a continuous service and an economy of power, since in cases where material has to be delivered at a lower level than the point at which it is shipped, the weight of the descending full trucks can be utilised to haul up ascending empty trucks. Spans of 2,000 feet or two-fifths of a mile are not at all unusual in very rough country where the spots on which supports can be erected are few and far between; but engineers naturally endeavour to make the span as short as possible, in order to be able to use a small size of rope.

Glancing at some interesting ropeways, we may first notice that used in the construction of the new Beachy Head Lighthouse, recently erected on the foreshore below the head on which the original structure stands. For the sake of convenience, the workshops, storage yards, etc., were placed on the cliffs, 400 feet above the sea and some 800 feet in a direct line from the site of the new lighthouse. Between the cliff summit and a staging in the sea were stretched two huge steel ropes, the one, six inches in circumference, for the track over which the four-ton blocks of granite used in the building, machinery, tools, etc., should be lowered; the other, 5-1/2 inches in circumference, for the return of the carriers and trucks containing workmen. The ropes had a breaking strain of 120 and 100 tons respectively; that is to say, if put in an hydraulic testing machine they would have withstood pulls equal to those exerted by masses of these weights hung on them. Their top ends were anchored in solid rock; their lower ends to a mass of concrete built up in the chalk forming the sea-bottom. When a granite block was attached to the carrier travelling on the rope, its weight was gradually transferred to the rope by lowering the truck on which it had arrived until the latter was clear of the block. As soon as the stone started on its journey the truck was lifted again to the level of the rails and trundled away. A brakesman, stationed at a point whence he could command the whole ropeway, had under his hand the brake wheels regulating the movements of the trailing ropes for lowering and hauling on the two tracks.

Another interesting ropeway is that at Hong-Kong, which transports the workmen in a sugar factory on the low, fever-breeding levels to their homes in the hills where they may sleep secure from noxious microbes. The carriers accommodate six men at a time, and move at the rate of eight miles an hour. The sensation of being hauled through mid-air must be an exhilarating one, and some of us would not mind changing places with the workmen for a trip or two, reassured by the fact that this ropeway has been in operation for several years without any accident.

In Southern India, in the Anamalai Hills, a ropeway is used for delivering sawn timber from the forests to a point 1-1/4 miles below. Prior to the establishment of this ropeway the logs were sent down a circuitous mountain track on bullock carts. Its erection was a matter of great difficulty, on account of the steep gradients and the dense and unhealthy forest through which a path had to be cut; not to mention the dragging uphill of a cable which, with the reel on which it was wound, weighed four tons. For this last operation the combined strength of nine elephants and a number of coolies had to be requisitioned, since the friction of the rope dragging on the ground was enormous. However, the engineers soon had the cable stretched over its supports, and the winding machinery in place at the top of the grade. The single rope serves for both up and down traffic; a central crossing station being provided at which the descending can pass the ascending carrier. Seven sleepers at a time are sent flying down the track at a rate of twenty miles an hour: a load departing every half-hour. The saving of labour, time, and expense is said to be very great, and when the saw mills have a larger output the economy of working will be still more remarkable.

The longest passenger ropeway ever built is probably that over the Chilkoot Pass in Alaska, which was constructed in 1897 and 1898 to transport miners from Dyea to Crater Lake on their way to the Yukon goldfields. From Crater Lake to the Klondike the Yukon River serves as a natural road, but the climb to its head waters was a matter of great difficulty, especially during the winter months, and accompanied by much suffering. But when the trestles had been erected for the fixed ropes, two in number, miners and their kits were hauled over the seven miles at little physical cost, though naturally the charges for transportation ruled higher than in less rugged regions. The opening of the White Pass Railway from Skagway has largely abolished the need for this cable track, which has nevertheless done very useful work. The Chilkoot ropeway has at least two spans of over 1,500 feet. As an engineering enterprise it claims our consideration, since the conveyance of ropes, timber, engines, etc., into so inhospitable a region, and the piecing of them together, demanded great persistence on the part of the engineers and their employés.