« PreviousContinue »
fumaces, as the nature of the metal requires by making a fire teneath it. Another dome is more or less heat to fuse it.
now constructed in the same manner, but the size Iron is inelted either in a blast furnace or cupo- and figure of the outside of the vessel : and upon la, which is a small cylindric furnace blown by this any rings, ornaments, &c. which are required, bellows or otherwise : and the metal and fuel are must be engraved. When dried, this dome must be put in together at top; and when melted the metal painted over with a blacking made of charcoal is let out at bottom, and conveyed to the mould ground up with water, and a good thickness of by a channel in the sand, if the work is large; or, loam is spread upon it. Iron wire and old hoops if smaller, it is received into a ladle called a shank, are worked up in it, to give it the necessary shewn at X, in fig. 6. It has three handles, and is strength. After drying this outer coat, the whole carried between two men, the double handles ke is turned over, and the bricks and loam of the first are very convenient for inclining the ladle to pour operation are removed ; leaving a hollow shell, as out the metal. It contains about an hundred the blacking prevents a connection of the two layweight; but for smaller quantities a single-handed ers of loam. CCC, fig. 9, is a section of this shell, laule is employed. For very heavy castings the shewing the manner in which it is placed over the metal is fused in what is called a reverberating core BB, so as to leave the dark space for the refurnace acting by the flame of the fuel alone. ception of the metal, which is poured in through Brass and the more valuable metals are melted two or more holes at dd. The mould must be bu. in erucibles, heated either in the blast furnace ried in a pit, and covered up with sand: long or in the air furnace, which is described in our round sticks are set up in the holes dd, to keep the article BRASS FOUNDERY. As the cupola and re- sand out of them : when drawn out they leave pasverberating furnaces are used in numerous other sages through the sand, down which the metal is processes in the arts, besides foundery, we shall del conveyed to the mould. Iron rings R, fig. 6. are seribe their construction under the article FURNACE. laid round the tops of the passages to prevent the
The sand moulds above described, by having metal breaking away the sand by its weight. The two or more flasks one upon the other, and divid- metal is always conveyed to such large moulds in ing the pattern into several parts, are applicable to channels cut out in the sand from the top hole of a very large proportion of the articles which come the furnace to the orifice of the mould. before the founder : but it is here proper to make A square cistern might be moulded in a similar the distinction between wet and dry sand. The manner by bricks and loam; and, with a reasonforier is used where the intricacy of the pattern able share of ingenuity, a founder will be able to requires the sand to be wetted to give it sufficient form a mould for any article he meets with. adhesion, and preserve its figure. When a mould FOUNDERY (Brass). The art of casting brass is of this kind is finished, it must be dried in a stove a distinct business from iron foundery, though to evaporate the water, before the casting. Dry the manner of moulding any article to be cast in sand is used for more simple patterns, and re- brass is the same as for iron; the difference lies quires no more water than may be suffered to re- in the manner of treating the metal in the turnace. main in the mould when cast without danger. Under our article Brass will be found an extract
Loam is also a material used by founders for from Dr. Rees'Cyclopedia, describing the process of making their moulds, when they are required of making brass as practised in Flintshire ; we are now such dimensions that the weight of so large a enabled to lay before our reader drawings of the body of sand would be too great to support itself furnace used for this process at Mr. Bennet's brass if rammed in flasks; also for others which are too works, Sheffield. The copper which is to be con. complicated to be moulded in sand: the loam is verted into brass is brought to the works in a graelay well mixed up with water, which is moulded nulated state, called shot copper, mare by melting while in a soft state and afterwards dried. To the copper and throwing it into cold water: 52 explain the art of moulding in loam, we shall de- pounds of copper in this state are mixed with 80 scribe the manner of making a mould for a large pounds of calamine previously prepared by calej. bemispherical bojler; and the reader will easily nation, which is performed in a reverberating furpereeive that a similar method is applicable to nace threeyards long, two yards wide, and the roof large bells, cylinders, cisterns, and many other 18 inches high; the calainine being thrown into articles. AA, fig. 8, pl. 74, represents the shape the furnace, and the name of pit coal reverberated of the boiler which is to be cast, in au inverted upon it from the roof of the furnace. In this manner state. The founder pruvides a round iron ring L, it is exposed to a considerable heat for about four fig. 7, somewhat larger than the intended boiler; hours, the attendant continually stirring it about upon this ring he erects a dome of brick work BB, with aniron hoe, and turningitorer, that every parfig. 9, rather smaller than the inside of the boiler; ticle may be equally subjected to the action of the when this is completed, an axis DD is erected, fire. By this operation the calamine is deprived of turning on pivots at its ends. The socket for the its sulphur, which passes off up the chimney, and is lower pivot is fixed in a stake driven in the ground precipitated on the ground around the furnace in beneath the dome, and the upper pivot turns in a such quantities as to be a considerable annoyance to socket fixed to the beam EÈ, in the roof of the any inhabitants of its vicinity. The calamine loses building. The axis DD has an arm F sliding upon in weight by the calcination: the large lumps of ca. it, wbich can be fixed at any height by a screw. lamine are now broken by a hammer, and the whole To this arm a piece of board G is screwed ; and its grourd to a fine powder between mill-stones like internal edge cut out to the curre the intended those used for grinding wheat; in this state the caboiler is to hare, and with a notch in the lower lamine is ready for making common brass. But for part proper to fit to the ring a at the bottom. making the best brass which is to be rolled or drawn After this preparation the moulder spreads a layer into wire, the calamine must be washed first beof wet loam upon the dome of brick work; and by fore grinding. It is washed in a cistern called a tarning the board G, and its axis Dround, the loam buddle, about six feet square, and 12 inches deep. will be scraped round to its true figure. By this A small stream of clean water is brought on, on means, in a short time, a core is formed the proper one side, and the waste flows out at the other. The size tu shape the inside of the vessel; and it is dried calamine being thrown into this buddle, and well
raked about, the water carries off a portion of It is on the wax that the several mouldings and calamine : by which separation the remainder other ornaments and inscriptions, to be representis found to be greatly iinproved for the purpose of ed în relievo on the outside of the bell, are forined. brass making. One bushel of pit-coal, ground to The clapper or longue is not properly a part of a tine powder, is now mixed up with 52 pounds of the bell, but is furnished from other hands. In slut copper, and 82 of prepared calamine; the inix- Europe it is usually of iron, with a large knob at ture is put in nine crucibles, one of which is shewn the extremity; and is suspended in the middle of at fig. 4, Plate 75. The crucibles are now placed the bell. In China, it is only a huge wooden malin the furnace, eight of them are ranged in a circle let, struck by force of arm against the bell; whence round the inside of the furnace as hewn at aaa in they can have but little of that consonancy so plan, fig. 1, and the ninth is placed in the center. much admired in some of our rings of bells. The The body of the furnace A A, fig. 1, 2, is nearly in Chinese have an extraordinary way of increasing the form of half an egg, that is, semi-spheroidal. the sound of their bells; viz. by leaving a hole The floor BB is an iron plate covered with clay under the cannon; which our bell-founders rather and perforated with 12 small holes, denoted by reckon a defect. dots in the plan, to bring up the supply of air. The proportions of our bells differ very much The top of the furnace has a round hole in it to in- from those of the Chinese. In ours, the modern troduce the crucibles and fuel, which is enclosed proportions are, to make the diameter fifteen times by a cover D, made of fine clay, with a small hole the thickness of the brim, and the height twelve in the center. EE is the flue forming a comaru- times. The parts of a bell are, 1. The sounding nication from the top of the furnace to the chiin- bow, terminated by an inferior circle, which grows ney, to convey away the smoke, and cause a thinner and thinner. 2. The brim, or that part of draught. The furnace is supplied with fresh air a' bell whereon the clapper strikes, and which is through the holes in the bottom of the furnace thicker than the rest. S. The outward sinking of from a large draught arch FF, which communica- the middle of the bell, or the point under which it ted with the open air. After the crucibles are placed grows wider to the brin. 4. The waist or furniin the furnace, a small quantity of furzens is ture, and the part that grows wider and thicker thrown down to prevent the 12 holes from being quite to the brim. 5. The upper vase, or that part stopped up by the coals with which the furnace, which is above the waist. 6. The pallet which is now filled. As it was heated red hot previous supports the staple of the clapper within. 7. The to being charged, the coals are quickly fired and bent and hollowed branches of metal uniting with the whole burns rapidly; the fire is continued for the cannons, to receive the iron keys, whereby the about twelve hours, the manager regulates its heat bell is hung up to the beam, which is its support from his experience of former processes, and and counterpoise, when rung out. forms his judgment of the actual state of the fur- The business of bell-foundery is reducible to nace from the appearance and colonr of the three particulars. I. The proportion of a bell. small stream of Aanie wbich issues from the small 2. The forming of the mould. And, 3. The meltkoled in the cover of the furnace mouth, when a ing of the metal. There are two kinds of propordamper at K in the flue E is closed so as to stop tions, viz. the sinple and the relative; the former the current of air going up the chimney. He iu- are those proportions only that are between the creases or diminishes the heat at pleasure, by several parts of a bell to render it sonorous; the opening or closing this damper, and thus regulate relative proportions establish a requisite harmony ing the draught. After the fire has been continued between several bells. about 12 hours, the crucibles are taken out by the The method of forming the profile of a bell, pretongs fig. 3. which have curved jaus kh, to embrace vious to its being ca t, in which the proportion of eoca crucible, and the contents of all the cight cru- the several parts may be seen, is as follows: The cibles poured into the centre one, from thence, it is thickness of the brim, ci in Plate 76, is the run into ingot moulds, tig. 5, each of the ingots i hus foundation of every other ineasure, and is divided formed wilt weigh about six pounds, and the whole into three equal parts. First, draw tbe line HD, quantity of brass produced by the operation is which represents the diameter of the bell; bisect about 80 pounds. The body of the furnace at AA it in F, and erect the perpendicular Ff; let DP is lined with fire-brick, and an iron ring is laid and HF be also bisected in E and G, and two other round the mouth, and upon which the cover shuts. perpendiculars Ee, Ga, be erected at E and G: The crucibles ave made of Stourbridge clay, inix- GE will be the diameter of the top or upper vase, ed up with old glass melting-pots, first reduced io ie. the diameter of the top will be half that of the a powler. An extensive brass work contains sev- bell; and it will therefore be the diameter of a eral furnaces which are arranged in two rows pa- bell which will sound an octave to the other. Dirallel to each other, and at sneh a distance apart, side the diameter of the bell, of the line HD, into that the flues of both rows may be carried up in fifteen : qual parts, and one of these will give CI the same stack of chimnies. Sometimes the brass the thickness of the brim; divide again each of is poured into moulds at once. l'ig. 6 shews a these fifteen equal parts into three other equal pair of flasks, AA the upper, BB the lower; oa parts, and then form a scale. From this scale take the pins to put them together, bb the holes for the twelve of the larger divisions or is of the whole metal.
scale in tlie compass, aud, setting one leg in D, - FOUNDERY OP BELLS.' The metal, it is to be describe an arc to cut the line Ee in N; draw ND, observed, is different for bells from what it is for and divide this line into twelve equal parts; at the statues, there being no tiu in the statue-metal: point 1 erect the perpendicular 1C=10, and CL but there is a fifth, and sometimes more, in the will be the thickness of the brim = ts of the diabell-metal.
meter: draw the line CD: bisect DN; and at the The dimensions of the core and the wax for point of bisection 6 erect tbe perpendicular bells, if a ring of bells especially, are not left to 6K=1} of the larger divisions on the scale. With Chance, but must be measured on a scale or dia- an opening of the compass equal to twice the pason, which gives the height, aperture, and thiek- length of the scale or thirty brims, setting one leg 115:, necessary for the several tunes required. in N, describe an arc.of a circle, and with the