II. Wooden Cylinder Bellows.

These are of various forms. We have seen square cylinders and round ones: the piston playing from the top, or from below; or the piston working in both directions. There are vertical and horizontal cylinders, and machines working with one, two, or three cylinders, with a dry receiver, water receiver, or with no receiver.

In our own country, we are almost entirely confined to one principal form, that is, the machine with two round tubs or bellowsthe piston working from below, and a dry receiver placed on the top of the tubs. This may be considered the best form of the wooden blast machine, if but a single stroke is desired. Fig. 132 is a representation of a blast machine of this kind; a, a are the bellows; Fig. 132.

b the receiver from which the sheet iron pipe c leads the blast to the furnace; d, d are the pistons, moved alternately by the beam

f, which is set in motion by the crank and wheel e. The wheel may be moved either by a waterwheel or a steam-engine. From eight to ten strokes is generally the speed required to supply a charcoal furnace. The tubs or cylinders, as well as the receiver, are generally from four to four and a half feet wide, and four feet high, making the stroke of the piston three feet. To the piston g, in the receiver, an iron rod is fastened, playing in a stuffing-box at the bottom, which carries a box h filled with iron or stones, to counterbalance the pressure of the blast, and to regulate it by playing up and down as the pressure from the tubs increases or diminishes. The valves are made of wood, lined with leather. The beam is generally laid below, and the tubs raised a few feet above ground. The whole machine is made of dry, well-seasoned wood -the cylinders glued: that is, composed of small segments of dry pine or ash, an inch or an inch and a half thick; the woody fibre thus runs around the cylinder, i. e. horizontally instead of vertically. This construction of the tubs secures greater permanency to their form. Their interior is in some instances, covered with a thin coating of a mixture of glue and plumbago, which gives it the appearance of iron, diminishes the friction, and secures a closer fit of the piston.

This kind of blast machine works admirably, if properly constructed; it is very durable. In every respect, this apparatus is preferable to the wooden bellows of the common form, such as that represented by Fig. 131. It can be erected at an expense of from $250 to $350. It will work one blast furnace for charcoal, or from four to five forge, or Catalan fires. A steam-engine or waterwheel of from twelve to sixteen horse power is required to put it in operation, and furnish the necessary blast for a blast furnace.

a. There are double working wooden tubs also in use, but not very frequently. These, in particular cases, may be of advantage; in cases, for instance, where room or expense is to be saved, or where wooden are very shortly to be replaced by iron cylinders. The wooden tubs are but a temporary arrangement, to gain time and means after the works are just started. The double working tubs, that is, those which make blast at each motion, like iron cylinders, offer no real advantages over the single; in fact, in ordinary cases, the tub with single stroke is preferable to the double tub. Among the advantages of the former, is the facility with which we can attend to the interior; in case damage is done to the

surface of the tub, it can be instantly mended. This is not the case with double stroke cylinders; here the top and bottom are closed, and the interior is not accessible without stopping the blast machine, and the operations which depend upon it. For these reasons, tubs which open at the top are preferable to those which open from below. The principal objection against wooden cylinders is that they are frequently severely rubbed by the packing of the piston; this diminishes the pressure of the blast in consequence of the leaking between the piston and tub. The disadvantages resulting from single stroke tubs, open from below, are more than counterbalanced by the greater simplicity of the piston rod, and the facility with which the valves can be adjusted. A stuffing-box is required, which, if the tubs are to be opened from above, must be made of iron. The expense of erecting a solid and strong frame to carry the crank and beam, is also comparatively great.

b. A good mechanic, and a thinking one, is required to construct a wooden blast machine. To put the wood well together is not sufficient; it is necessary to select it with due relation to its liability to twist, warp, and crack. All curly, knotty wood, and wood from the heart of the tree, must be rejected. The circumference of the tree, or both seams of the heart plank alone, are to be used for the tubs and receiver. The tops as well as the tubs are generally three inches thick. The latter are glued together from segments one foot or more in length, and not more than one and a half inch thick, as before stated. The tops and pistons are composed of strips of plank not more than three or four inches wide, grooved and feathered, and well glued. Ash may be considered the best wood for making the tubs; but good dry pine will answer. Other kinds of wood, such as maple and walnut, are too apt to warp, and therefore ought not to be used. To keep the interior slippery and sound, the surface of the tub is frequently brushed over with plumbago, or soapstone powder, or with a mixture of both. These ingredients are moistened with water, to which a little glue may be added. Fat or oil is an improper material with which to lubricate the surface of a wooden tub, for both are very soon destroyed; the destruction of the piston and the wood of the cylinder then follows, to the injury of the machine, and the loss of blast.

Square tubs, and horizontal tubs of double stroke, have been tried; but, it appears, with no good advantage, for nobody now thinks of such forms. It is unnecessary to speak of these machines

in this place, as they belong to antiquity, and are, at the present time, of no practical importance.

III. Iron Cylinder Blast Machines.

a. There are various forms of these machines. The smallest, but not the most simple, apparatus, is a double stroke cylinder-that is, composed of two beams and two cylinders-which is frequently met with at the Western establishments. In rolling mills, it is used to blow the finery; we find it also at blast furnaces. Fig. 133

Fig. 133.

Iron cylinder bellows.

exhibits it so plainly, that a particular description of it is unnecessary. This machine makes an excellent blast. Its cost is the main objection to its use; this objection is valid, as far as the first outlay is concerned; but its expensiveness is counterbalanced by the excellent manner in which it works. It does not make quite a regular blast, if worked without a receiver; but even in this case, it may be made to work better than others differently constructed. In this machine, the cylinders, pistons, pipes, valves, wheels, and cranks are all of iron, except the beams and pitmans, which are of wood; but

the latter would be better if made also of iron. This machine is constructed on an excellent principle, and is superior to the horizontal cylinder, very much used in the Eastern States. This is finding its way to the Western States, which does not augur well for the speedy and successful application of stone coal in the blast furnace of that section of our country.

b. The desire of constructing a cheap apparatus has led to the making of an iron cylinder blast machine with a horizontal instead of a vertical motion of the piston, as shown in Fig. 134. There is no doubt that such a machine is far cheaper than one of vertical stroke; but, when we consider the difficulty of keeping the packing tight, and the loss of blast which thence ensues, and the frequent disturbances which originate from very hard rubbing of the piston on one part of the cylinder alone, it may be doubted whether it should be considered a useful apparatus; in fact, experience rather bears against than confirms its utility. Fig. 134 exhibits such a cylinder.

The piston rod runs through both heads, to carry the weight of the piston, and prevent its rubbing with all its strength on the lower part of the cylinder. The valves are generally made of sheet iron lined with leather. Machines of this construction have their advantages, besides the great simplicity in their entire arrangement which they afford. There is no difficulty in procuring a solid foundation for the whole. The weight of the pistón, piston rod, and pitman, which is objectionable in vertical machines propelled by a waterwheel, particularly in those where but one cylinder is employed, is, in this case, almost balanced. The crank and a small portion of the pitman form the only weight which is not equipoised. The application of the valves is very simple, and very correct. They must be suspended vertically in a good blast machine.