Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/49

 Jan. 12, 1872. tory. It was necessary to provide against the pressure of the metal on the walls of the cope; the cope was therefore built in the ground of Yin. brick- work, well rammed up all round to the level of the surface, for although the core had to be broken down for each casting, the cope, as far as the brickwork was concerned, remained permanent, and served for all the succeeding castings of the same form and size. When the pit was dug the loam-ring was laid in position, and upon this the wall was built. ‘These rings were generally cast in one piece, but for want of space in the foundry at the time, the ring was made in three segments, and bolted together ; and as it was proposed to cast the conical cylinders in the same pit, a strong cast iron cross was pro- vided, and laid permanently at the bottom of the pit, with its twelve arms passing under the loam- ring, so that it could be used to bolt down the coni- cal cores withont interfering with the cope of the first cylinders. The loam-ring for the cope was 18in. wide and 2kin. thick, and cast with twelve lugs round the cirenmference, to which lugs were attached the tying-down bolts, consisting of 1Jin. ronnd rods, forged with stirrups fitting the lugs of the loam-ring. The weight of metal in the ring and cross amounts to about seven tons. The cope was built up of Qin. brickwork, with binding plates set in the joints at about every six courses. The plates were jin. thick, and 9in. wide; the walls were well rammed up all round and thoroughly dried. Thus far the structure is permanent, and remains in situ. The walls are faced inside with a coat of loam struck up in the ordinary way by means of the loam-boards; these, however, from their extra weight and size, required to be counter- balanced, otherwise the process differs in no way from the general plan adopted in all like cases. In striking up the cope a seating of about Gin. in depth is formed at the bottom of the mould; a similar seating called a dummy is also formed on the floor where the core is to be built up; this seating serves for all the succeeding cores; the core being constructed on this dummy corresponds exactly with the seating at the bottom of the cope, and when placed in position is guided by it into the centre, leaving the desired space all round for the metal, The core is made on a ring cast rather smaller than the seating, with eight wrought iron loops cast in, by which the whole is lifted and placed in the cope; upon this ring are eight, segmental plates, which carry the brickwork. These plates are clamped together, forming one ring, but as soon as the casting is made the clamps are knocked away, and the plates set free to allow for the contraction of the metal in cooling. At every six courses in the wall are binding plates in segments to strengthen the work, and the brickwork is 9in. thick all over. The core thus constructed weighs eighteen tons, In the first or lowest cylinder a curved moulding is formed on the bottom edge, for as no flange is here required it was thought advisable to strengthen the edge which bears on the ground and carries the weight of the superstructure; and at the same time something of the sort was required to equalise the metal, so as to avoid the chance of a fracture from any irregularity in the cooling. All these cylinders, it must be stated, are cast the reverse way to the position in which tl:ey will stand in the piers, in order that they may be relieved from the mould without breaking down the cope. The covering plate, which is cast in three segments, is struck up to the form of the bottom moulding of the cylin ders; this, from their being reversed in the mould, being at the top, it corresponds with and fits into a seating formed on the top of the cope, and is cast with thirty-three holes, thirty of which serve for the runners, and three for the risers. These seg- ments were capable of being dried in the stoves; but in order to dry the rest of the work, “ portable kettles,” as they are called, are employed: in these, gas-coke is burnt, and of course this is not so eco- nomical as drying in stoves; but the stoves at the Battersea Foundry will not take in a mould more than 14ft. wide. When the bricks and loam are dry, the face of the mould is blacked, and then again dried, and the mould is then put together. A cast iron cross having twelve arms is laid over all, and tied down by the twelve 1}in. bolts surrounding the cope. In making up the mould a sow or trough is formed, composed of sand and confined between two rows of jointed plates, called cribs, fixed on edge all round the top of the mould. In this sow are thirty runners of about 1iin. diameter, leading perpendicularly through the holes in the covering plate down into the mould between the cope and core. Three other holes of similar size, which serve as risers, are stopped off from the runners on one side of the mould. Three basins communicating with the sow are formed to receive first the metal from the ladles. The metal when poured is thus con- THE BUILDING NEWS. 33 ducted into the mould in thirty small streams, which ensures a uniform flow to all parts at once. The calculated weight of th2 casting is about nine tons, but as it is always desirable to have metal enough, and to spare, it is run from three ladles, a six ton, a four ton, and a three ton, making in all about thirteen tons of metal. The arrangement adopted of pouring the metal out at three founts is very satisfactory. The largest ladle is served by the traveller, and the other two by the cranes, one being close to the work, and the other about twelve feet off, from which the metal flows to the mould along a trough. The metal is melted in two cupolas, one 3ft. internal diameter, and the other 2ft. 6in, The largest cupola has three tuyeres, the smaller one two. A pressure of Tin. of blast was got with one of Lloyd’s 30in. fans, driven by an eight horse- engine, and the thirteen tons of metal was run down in about an hour and a half. A mixture of one-fourth pig iron and three-fourths best machine scrap is employed, which produces a metal extremely strong and suitable for the purpose. The conical cast- ings forming that portion of the piers of the bridge which reduces the diameter from 21ft. to 15ft. require rather a different arrangement with regard to the building-up of the core. The angle of the cone is so great, contracting as the cylinders do 3ft. on each side in a height of 4ft. 6in., that it would be impracticable to lay on the loam overhead, as it were; it would not have adhered to the brickwork, but would have fallen off as soon as the board left it. The plan was therefore adopted of thicknessing up the cope and building the core within it. The cope of the conical cylinders is built inside that of the parallel ones, as there are some more to cast after these are done. When the cope is struck up in loam and dried, a thickness of wet sand, cor- responding with the thickness of the casting, is laid on and struck up with the core-board and dried. The core is then built inside the cope, and when dry is lifted out and dressed, and the thickness of sand re- moved ; in all other respects the casting is conducted as usual, except that as these castings present more surface on plan, they require extra holding down, which was effected by means of cast iron clamps on the inside, in addition to the twelve external tie- bolts. The 15ft. cylinders are made in every re~ spect ina similar way to the 21ft. ones, allowance being made for the difference in size only. They weigh only about 7 tons, and it takes a week to prepare each mould. Mr. Kingsford concluded his paper by some remarks on the estimation of the several strains that are set up in the moulds during the time of pouring in the metal for these large cast- ings. In the case of the 21ft. cylinders the width of the flange was 4in., the circumference being 66ft., giving an area of 22 square feet, multiplied by 4ft. 6in., the height of the evlinder; this equals 99 cubic feet of displacement, and as a cubic foot of iron weighs 4ewt. there is about 20 tons exerting itself to lift the core. In the conical castings the flotation is considerably more. The difference of areas between the cylinder at the bottom and top of the mould represents about 190 square feet; this, multiplied by 4ft. 6in., the height, gives 855 cubic feet of dis- placement, being equal to 170 tons. From this we must deduct about 20 tons for the weight of the core, which represents a vessel floating in liquid iron, and 150 tons is the upward pressure on the tying- down bolts. There are twelve 1}in. bolts, equal to 27 circular inches, 10 tons to a circular inch being generally considered safe. This gives 270 tons, which should be sufficient; but in order to be on the safe side, the mould is clamped on the inside, which greatly adds to its rigidity, the object being to guard against the mould straining as much as possible. Besides the actual strain from the pressure of the metal exerted to float the core there is the lateral pressure on the walls of the core and cope. The cope being in the ground and well rammed up may be passed by as safe ; but the core requires very careful construction. Eight of these cylinders, out of about thirty, have been cast. The core of the first, as before stated, was not sufficiently strong enough to bear the weight of the metal against its sides, and it gave way. The second strained so much that instead of its thickness averaging 1gin., as it ought to have done, it averages 2in., and weighs 12 tons. The succeeding ones have not strained much, but the lightest is fully Jin. thicker than it ought to be, and Mr. Kingsford believed that in order (o cast them without straining in the least the walls of the core would have to be 18in. thick, and the core would weigh upwards of 30 tons. Now that it is possible from practice, however, to judge the amount of the strain in the castings it was allowed for, and the remaining cylinders will be nearly correct as to thickness. Another cause of straining is the pres- sure of the suddenly heated air in the mould as soon as the melted iron isrun in, ‘This is not so easily calculated, but it is necessary, in order to have a good sound casting, free from scabs, that the air should be thus confined, The metal enters by thirty Tunners, and the same quantity of air, greatly augmented in bulk, has to escape through three risers, which it does, in all probability, at a pressure of nearly 15Ib. to lin. If so, it would just about double all the strains, for one inch of iron, 4ft. 6in. high, equals about 14 tons or 15 tons. A brief discussion ensued, and the thanks of the members having been voted to Mr. Kingsford for his interesting paper, the proceedings terminated. ——_ @—____ THE TIMBER TRADE OF 1871. (From Churchill and Sim's Circular.) Te gross imports of 4,000,000 loads of wood, which we last year commented on as the largest ever known, has this year again increased 10 per cent., or a total of 4,500,000 loads, and this in- crease is entirely in the import from the North of Europe, that from Canada having been stationary for some years. It is not surprising that the Canadian trade should not increase in the same ratio as the European, when we consider—firstly, the difference of freight from America, which is nearly double that from the Baltic, and in an article of small value in comparison with its bulk, freight is a large item of cost; and, secondly, the large and ever-increasing demand in the United States, by which the value of wood in Canada is being enhanced every year. The proprietors of saw-mills in the North of Europe propose to take full advantage of this increase of trade, and of the competition of English buyers for the well-known stocks, and are asking largely-advanced prices for this season’s shipments. The increase of production likely to be stimulated by these advanced prices, however, will sooner or later overtake the increase of demand, and the inevitable reaction from high to low prices will follow. It must, however, be remembered that the prices of wood will in course of years be aways rising, as the cost of labour is always increasing. The wood growing in the most convenient situations for shipment is being exhausted, and for the trans- port from greater distances, the navigation of rivers has to be improved, or railways have to be made to being the blocks to the saw-mills, or the sawn wood to the shipping ports, The London importa- tion has not kept pace with that to outports, but it appears to have been just sufficient for the consump- tion, the stocks on the whole being about the same as at the beginning of last year, showing, however, some increase in foreign deals, counterbalanced by a decrease in colonial deals. We look forward with confidence that the consumption in the year 1872 will continue on alarge scale, and that if the cost of wood be not too much enhanced, there is a good pros- pect of a year of prosperity for the importers and dealers. eee ne ees DAMP HOUSES. [ is by no means easy (says the Field) to pre- vent damp from rising from the soil to the house ; it is a much easier thing to prevent moisture (the cause of the damp) from lodging and remaining in the soil, and it is worth knowing that it is so. If it had been known earlier, and when known acted upon, the number of damp houses would be much less than it is now. Let the site of the house—and the larger the area operated upon the better—be drained precisely after the fashion a field is drained, and there will be little moisture in the soil from which damp can arise. Let the whole area be surrounded by catch drains, and the area in the direction of its length or breadth, aceording to the fall or inclination of the ground, be divided into spaces by parallel drains, all of which discharge their water in the main drain leading to the outfall. We need scarcely say that the drains should be placed deep, not less in heavy soils than 4ft. 6in. The drains, or rather the trenches, may be filled up with stones, if these be plentiful, or, better still, the ordinary field-drain tube. A good deal depends also upon the position of the site; some pay so little attention to this that they build on the spot the best calculated to catch the water and retain it. Let the ground be rising, or on a slope, so that the drainage of the soil will be easily carried out; never build in a hole. This advice, ought, we think, to be unnecessary; it is not so, seeing how often houses are built in holes or depressions, Further, build the house pretty well off the gronnd, so as to rise to the ground-floor level by three steps at the least. Some like to burrow so much that they will actually descend to their houses—a most pernicious system. Where expense is no object, but having a house as comfortable as possible is the aim, we should recom- mend the whole house to be cellared under, and all the cellar floors laid with Portland cement concrete,