Discoveries and Inventions of the Nineteenth Century

Several forms of rock-drills, or perforators, have been constructed on the same principle as that used in the Mont Cenis Tunnel, and a description of one of them will give a good notion of the general principle of all. We select a form devised by Mr. C. Burleigh, and much used in America, where it has been very successfully employed in driving the Hoosac Tunnel, effecting a saving in the cost of the drilling amounting to one-third of the expense of that operation, and effecting also a still greater saving of time, for the tunnel, which is 5 miles in length, is to be completed in four years, instead of twelve, as the machines make an advance of 150 ft. per month, whereas the rate by hand labour was only 49 ft. per month. These machines are known as the “Burleigh Rock Drills,” and have been patented in England for certain improvements by Mr. T. Brown, who has kindly supplied us with the following particulars: Fig. 180.—Burleigh Rock Drill on Tripod. The Burleigh perforator acts by repeated blows, like Bartlett and Sommeiller’s, but its construction is more simple, and the machine is lighter and not half the size, while its action is even superior in rapidity and force. The Burleigh machines are composed of a single cylinder, the compressed air or steam acting directly on the piston, without the necessity of flywheel, gearing, or shafting. The regular rotation of the drills is obtained by means of a remarkably simple mechanical contrivance. This consists of two grooves, one rectilinear, the other in the form of a spiral cut into the piston-rod. In each of these channels, or grooves, is a pin, which works freely in their interior: these pins are respectively fixed to a concentric ring on the piston-rod. A ratchet wheel holds the ring, and the pin slides into the curve, causing it to turn always in the same direction, without being able to go back. By this eminently simple piece of mechanism, the regular rotation of the drill-holder is secured. The slide-valve is put into motion by the action of a projection, or ball-headed piston-rod, on a double curved momentum-piece, or trigger, which is attached to the slide-rod or spindle by a fork, thus opening and shutting the valve in the ascent and descent of the piston. Fig. 180 represents one of the machines attached in this instance by a clamp to the frame of a tripod. The principal parts 356of the machine are the cylinder, with its piston, and the cradle with guide-ways, in which the cylinder travels. The action of the piston is similar to that of the ordinary steam hammer, with this difference, that, in addition to the reciprocating, it has also a rotary, motion. The drill-point is held in a slip-socket, or clamp, at the end of the piston-rod, by means of bolts and nuts. The drill-point rotates regularly at each stroke of the piston, making a complete revolution in every eighteen strokes. For hard rocks it is generally made with four cutting edges, in the form of a St. Andrew’s cross, 357thus striking the rock in seventy-two places in one revolution, each cutting edge chipping off a little of the stone at each stroke in advance of the one preceding. The jumper makes, on an average, 300 blows per minute, and such is the construction of the machine, that the blows are of an elastic, and not of a rigid, nature, thus preventing the drill-point from being soon blunted. It has been found in practice, that a drill-point used in the Burleigh machine can bore on an average 20 ft. of Aberdeen granite without re-sharpening. As the drill pierces the rock, the machine is fed down the guide-ways of the cradle by means of the feed-screw (see Fig. 180), according to the nature of the rock and the progress made. When the cylinder has been fed down the entire length of the feed-screw, and if a greater depth of hole is required, the cylinder is run back, and a longer drill is inserted in the socket at the end of the piston-rod. The universal clamp may be attached to any form of tripod, carriage, or frame, according to the requirements of the work to be done; it enables the machines to work vertically, horizontally, or at any angle. The following advantages are claimed for this machine: Any labourer can work it; it combines strength, lightness, and compactness in a remarkable degree, is easily handled, and is not liable to get out of order. No part of the mechanism is exposed; it is all enclosed within the cylinder, so there is no risk of its being broken. It is applicable to every form of rockwork, such as tunnelling, mining, quarrying, open cutting, shaft-sinking, or submarine drilling; and in hard rock, like granite, gneiss, ironstone, or quartz, the machine will, according to size, progress at the incredible rate of four inches to twelve inches per minute, and bore holes from ¾ in. up to 5 in. diameter. It will, on an average, go through 120 ft. of rock per day, making forty holes, each from 2 ft. to 3 ft. deep, and it can be used at any angle and in any direction, and will drill and clear itself to any depth up to 20 ft. The following extract from the “Times,” September 24th, 1873, gives an account of some experiments with the machine, made at the meeting of the British Association in that year, before the members of the Section of Mechanical Science: “Yesterday, considerable interest was taken in this section, as it had been announced that a ‘Burleigh Rock Drilling Machine’ would be working during the reading of a paper by Mr. John Plant. The machine was not, however, in the room, but was placed in the grounds outside, where it was closely examined by the members after the adjournment, and seen in full operation, boring into an enormous block of granite. The aspect of the machine cannot be called formidable in any respect, for it looks like a big garden syringe, supported upon a splendid tripod; but when at work, under about 80 lbs. pressure of compressed air, it would be deemed a very revolutionary agent indeed, against whose future power the advocates for manual labour in the open quarry, the tunnel, and even the deep mine, may well look aghast. Placed upon a block of granite a yard deep, the machine was handled and its parts moved by the fair hands of many of the lady associates of scientific proclivities; but once the source of power was turned on, the drill began its poundings, eating holes 2 in. in diameter in the block of granite, and making a honeycomb of it as easily as a schoolboy would demolish a sponge cake. It pounds away at the rate of 300 strokes, and progresses forward about 12 in., in the minute, making a complete revolution of the drill in eighteen strokes, and keeping the hole free of the pounded rock. The machine was fixed to work at any angle, almost as 358readily as a fireman can work his hose; and its adaptation to a wide range of stone-getting, by drilling for blasting, and cutting large blocks for building and engineering, with a saving of capital and labour, was admitted by many members of the section. The tool is called the ‘Burleigh Rock Drill,’ invented by Mr. Charles Burleigh, a gentleman hailing from Massachusetts, United States. The patent is the property of Messrs. T. Brown and Co., of London. The principal feature of this new machine is, that it imitates in every way the action of the quarryman in boring a hole in the rock.” Fig. 181.—Burleigh Rock Drill on Movable Column. Many forms of carriages and supports have, from time to time, been made to suit the work for which the ‘Burleigh’ machines have been required. The machine is attached to these carriages, or supports, by means of the universal clamp, by which it can be worked in any direction and at any angle. Of these carriages we select for notice only two forms, one of which is shown in Fig. 181. This carriage can be used to great 359advantage in adits and drifts. It consists of an upright column, with a screw clamp-nut for holding and raising or lowering the machine, the whole being mounted on a platform which can slide right across the carriage, and thus the machine can be brought to work on any point of a heading. It is secured in position by means of a jack-screw in the top of the column; and as the carriage is mounted on wheels, it is easily moved to permit of blasting. Fig. 182 represents a carriage which is the result of many years’ experience with mining machinery, and it is considered a very perfect appliance. It is constructed of wood and iron, and it runs on wheels. The supports for the machines, four of which may be mounted at once, are two horizontal bars, the lower of which can be raised or lowered, as may be necessary. The two parallel sides of the carriage are joined only at the upper side, and there is nothing to prevent it from being run into the heading, though the way between the rails may be heaped up with broken rock, if only the rails are clear. Drilling, and the removal of the broken rock, may then proceed simultaneously; for, by means of a narrow gauge inside the carriage rails, small cars may be taken right up to the débris. It is made in different sizes, to suit the dimensions of the tunnel required. To give the carriage steadiness in working, it is raised from the wheels by jack-screws, and held in position by screws in a similar manner to the carriage represented in Fig. 181. Fig. 182.—Burleigh Rock Drills mounted on a Carriage. Fig. 183. An extremely interesting system of drilling rocks—totally different from that on which the machines we have just described are constructed—has, within the last few years, been introduced by Messrs. Beaumont and Appleby. What does the reader think of boring holes in rocks with diamonds? It has long been a matter of common knowledge that the diamond 360is the hardest of all substances, and that it will scratch and wear down any other substances, while it cannot itself be scratched or worn by anything but diamond. In respect to wearing down or abrading hard stones, the diamond, according to experiments recently made by Major Beaumont, occupies a position over all other gems and minerals to a degree far beyond that which has been generally attributed to it; for in these experiments it was found that on applying a diamond, or rather a piece of the “carbonate” about to be described, fixed in a suitable holder, to a grindstone in rapid rotation, the grindstone was quickly worn down; but on repeating a similar experiment with sapphires and with corundum, it was these which were worn down by the grindstone. Without, on the present occasion, entering into the natural history of the diamond, we may say that there are, besides the pure colourless transparent crystals so highly prized as gems, several varieties of diamond, and that those which are tinged with pink, blue, or yellow, are far from having the same value for the jeweller. Then there is another impure variety called boort, which appears to be employed only to furnish a powder by which the brilliants are ground and polished. In the diamond gravels of Brazil, from which we derive our regular supply of these gems, there was discovered in 1842 a curious variety of dark-coloured diamond, in which the crystalline cleavage, or tendency to split in certain directions (which belongs to the ordinary stones), appears to be almost absent; and the substance might be regarded as a transition form between the diamond and graphite but for its hardness. This substance was until lately used for the same purposes as boort, which is a nearer relative of the pure crystal, and like it, splits along certain planes. It received