Chapter 6

The drum is 6.08 m. diameter, the breadth being 2.04 m., with a total weight of 33,000 kilos. The beams are of cast iron with balance weights cast on. The connecting rods and cross beams are of wrought iron, and the cranks, crank shaft, piston rods, valve rods, etc., of steel. The bed-plate for the main shaft bearings are cast in one piece with the standards for the beam, which are connected firmly together by the center bearing, M M1, which is cast in one piece, and also by the diagonal bracing piece, N N1. The construction of the cylinder and valve chests is shown in Fig. 1. The working cylinder is in the form of a liner to the cylinder, thus forming the steam jacket, with a view to future renewal. This lining has a flange at the lower part for bolting it down, being made steam-tight by the intervention of a copper packing ring. There is a similar ring at the upper part which is pressed down by the cylinder cover. The latter is cast hollow and strengthened by ribs. The pistons are provided with cast iron double self-expanding packing rings. For preventing accidents by condensed water, spring safety valves, ss and s1 s1, are connected to the valve chests. The valve gear, which is arranged in the same manner for both cylinders, is actuated by shafts, w and w1, rotated by toothed wheels as shown. Motion is communicated from the way-shafts, w and w1, by the eccentrics, and the eccentric rods, e1 e2 e3 e4, and the levers and rods belonging thereto, to the short steam valve rocking shafts levers, f1 f2 f3 f4, and the exhaust valve rocking shafts, k1 k2 k3 k4, the bearings of which are carried on brackets above the valve chests, which, being furnished with tappet levers, raise and lower the valves.

The valves are conical, double-seated, and of cast iron, and the inlet and outlet valves are placed the one above the other, the seats being also conically ground and inserted through the cover of the valve chest. Both inlet and outlet valves are actuated from above, and are removable upward, an arrangement which admits of the valves being more easily examined than when the two are actuated from different sides of the valve chest. To carry out this idea the inlet valves are furnished with two guides, which, passing upward through the stuffing-box, are attached to a hard steel cross piece, which receives the action of a bent catch turning on a pin attached to the levers, t1, t2, t3, t4. The exhaust valves, on the contrary, have only one guide each, which passes upward through the seat of the admission valve, through the valve itself by means of a collar, and through the stuffing-box. It is furnished with hard steel armatures, through which the levers, z1 z2, Fig. 3, act upon the exhaust valves.

The governor effects the acceleration or retardation of the loosening of the catch actuating the steam valve by means of hard steel projections on the shaft, v1, the position of which, by means of levers, is regulated by the governor, which in its highest position does not allow the lifting of the inlet valve at all. The regulation of the expansion by the governor from 0 to 0.45 takes place generally only in the case of the high-pressure cylinder, while the low-pressure cylinder has a fixed rate of expansion. Only when the low-pressure cylinder is required to work with steam direct from the boiler is the governor applied to regulate the expansion in it. An exact action in the valve guides and a regular descent is secured by furnishing them with small dash pot pistons working in cylinders. Into them the air is readily admitted by a small India-rubber valve, but the passage out again is controlled at pleasure.--_The Engineer_.

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TO DETECT ALKALIES IN NITRATE OF SILVER--Stolba recommends the salt to be dissolved in the smallest quantity of water, and to add to the filtered solution hydrofluosilicic acid, drop by drop. Should a turbidity appear an alkaline salt is present. But should the liquid remain limpid, an equal volume of alcohol is to be added, which will cause a precipitate in case the slightest trace of an alkali be present.

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POWER HAMMERS WITH MOVABLE FULCRUM.

[Footnote: Paper read before the Institution of Mechanical Engineers.--_Engineering_.]

By DANIEL LONGWORTH, of London.

The movable-fulcrum power hammer was designed by the writer about five and a half years ago, to meet a want in the market for a power hammer which, while under the complete control of only one workman, could produce blows of varying forces without alteration in the rapidity with which they were given. It was also necessary that the vibration and shock of the hammer head should not be transmitted to the driving mechanism, and that the latter should be free from noise and liability to derangement. The various uses to which the movable fulcrum hammers have been put, and their success in working[1]--as well as the importance of the general subject which includes them, namely, the substitution of stored power for human effort--form the author's excuse for now occupying the time of the meeting.

[Footnote 1: The hammers have been for some years used by A. Bamlett, of Thirsk; the American Tool Company, of Antwerp; Messrs. W.&T. Avery, of Birmingham; Pullar & Sons, of Perth; Salter & Co., of West Bromwich; Vernon Hope & Co., of Wednesbury, etc.; and also for stamps by Messrs. Collins & Co., of Birmingham, etc.]

Until these hammers were introduced, no satisfactory method had been devised for altering the force of the blow. The plan generally adopted was to have either a tightening pulley acting on the driving belt, a friction driving clutch, or a simple brake on the driving pulley, put in action by the hand or foot of the workman. Heavy blows were produced by simply increasing the number of blows per minute (and therefore the velocity), and light blows by diminishing it--a plan which was quite contrary to the true requirements of the case. To prevent the shock of the hammer head being communicated to the driving gear, an elastic connection was usually formed between them, consisting of a steel spring or a cushion of compressed air. With the steel spring, the variation which could be given in the thickness of the work under the hammer was very limited, owing to the risk of breaking the spring; but with the compressed air or pneumatic connection the work might vary considerably in thickness, say from 0 to 8 in. with a hammer weighing 400lb. The pneumatic hammers had a crank, with a connecting rod or a slotted crossbar on the piston-rod, a piston and a cylinder which formed the hammer-head. The piston-rod was packed with a cup leather, or with ordinary packing, the latter required to be adjusted with the greatest nicety, otherwise the piston struck the hammer before lifting it, or else the force of the blow was considerably diminished. As the piston moved with the same velocity during its upward and downward strokes, and, in the latter, had to overtake and outrun the hammer falling under the action of gravity, the air was not compressed sufficiently to give a sharp blow at ordinary working speeds, and a much heavier hammer was required than if the velocity of the piston had been accelerated to a greater degree.

As it is impossible in the limits of this paper to describe all the forms in which the movable fulcrum hammers have been arranged, two types only will be selected taken from actual work; namely, a small planishing hammer, and a medium-sized forging hammer.[1]

[Footnote 1: To the makers, Messrs. J. Scott Rawlings & Co, of Birmingham, the author is indebted for the working drawings of these hammers.]

The small planishing hammer, Figs. 1 to 3, next page, is used for copper, tin, electro, and iron plate, for scythes, and other thin work, for which it is sufficient to adjust the force of the blow once for all by hand, according to the thickness and quality of the material before commencing to hammer it. The hammer weighs 15 lb., and has a stroke variable from 2½ in. to 9½ in., and makes 250 blows per minute. The driving shaft, A, is fitted with fast and loose belt pulleys, the belt fork being connected to the pedal, P, which when pressed down by the foot of the workman, slides the driving belt on to the fast pulley and starts the hammer; when the foot is taken off the pedal, the weight on the latter moves the belt quickly on to the loose pulley, and the hammer is stopped. The flywheel on the shaft, A, is weighted on one side, so that it causes the hammer to stop at the top of its stroke after working; thus enabling the material to be placed on the anvil before starting the hammer. The movable fulcrum, B, consists of a stud, free to slide in a slot, C, in the framing, and held in position by a nut and toothed washer. On the fulcrum is mounted the socket, D, through which passes freely a round bar or rocking lever, E, attached at one end to the main piston, F, of the hammer, G, and having at the other extremity a long slide, H, mounted upon it. This slide is carried on the crank-pin, I, fastened to the disk, J, attached to the driving shaft, A. The crank-pin, in revolving, reciprocates the rocking lever, E, and main piston, F, and through the medium of the pneumatic connection, the hammer, G. The slide, H, in revolving with the crank-pin, also moves backward and forward along the rocking lever, approaching the fulcrum, B, during the down-stroke of the hammer, and receding from it during the up-stroke. By this means the velocity of the hammer is considerably accelerated in its downward stroke, causing a sharp blow to be given while it is gently raised during its upward stroke.

To alter the force of the blow, the hammer, G, is made to rise and fall through a greater or less distance, as may be required, from the fixed anvil block, K, after the manner of the smith giving heavy or light blows on his anvil. It is evident that this special alteration of the stroke could not be obtained by altering the throw of a simple crank and connecting rod; but by placing the slot, C, parallel with the direction of the rocking lever, E, when the latter is in its lowest position, with the hammer resting on the anvil, and with the crank at the top of its stroke, this lowest position of the rocking lever and hammer is made constant, no matter what position the fulcrum, B, may have in the slot, C. To obtain a short stroke, and consequently a light blow, the fulcrum is moved in the slot toward the hammer, G; and to produce a long stroke and heavy blow the fulcrum is moved in the opposite direction.

Fig. 3 gives the details of the pneumatic connection between the main piston and the hammer, in which packing and packing glands are dispensed with. The hammer, G, is of cast steel, bored out to fit the main piston, F, the latter being also bored out to receive an internal piston, L. A pin, M, passing freely through slots in the main piston, F, connects rigidly the internal piston, L, with the hammer, G. When the main piston is raised by the rocking lever, the air in the space, X, between the main and internal pistons, is compressed, and forms an elastic medium for lifting the hammer; when the main piston is moved down, the air in the space, Y, is compressed in its turn, and the hammer forced down to give the blow. Two holes drilled in the side of the hammer renew the air automatically in the spaces, X and Y, at each blow of the hammer.

Figs. 4 to 6, on the next page, represent the medium size forging hammer, for making forgings in dies, swaging and tilting bars, and plating edged tools, etc.

The hammer weighs 1 cwt., has a stroke variable from 4 in. to 14½ in., and gives 200 blows per minute; the compressed air space between the main piston and the hammer is sufficiently long to admit forgings up to 3 in. thick under the hammer.

To make forgings economically, it is necessary to bring them into the desired form by a few heavy blows, while the material is still in a highly plastic condition, and then to finish them by a succession of lighter blows. The heavy blows should be given at a slower rate than the lighter ones, to allow time for turning the work in the dies or on the anvil, and so to avoid the risk of spoiling it. In forging with the steam hammer the workman requires an assistant, who, with the lever of the valve motion in hand, obeys his directions as to starting and stopping, heavy or light blows, slow or quick blows, etc; the quickest speed attainable depending on the speed of the arm of the assistant. In the movable-fulcrum forging hammer the operations of starting and stopping, and the giving of heavy or light blows, are under the complete control of one foot of the workman, who requires therefore no assistant; and by properly proportioning the diameter of the driving pulley and size of belt to the hammer, the heavy blows are given at a slower rate than the light ones, owing to the greater resistance which they offer to the driving belt.

In this hammer the pneumatic connection, the arrangements for the starting, stopping, and holding up of the hammer, as well as those for communicating the motion of the crank-pin to the hammer by means of a rocking lever and movable fulcrum, are similar to those in the planishing hammer, differing only in the details, which provide double guides and bearings for the principal working parts.

The movable fulcrum, B, Figs. 4 and 5, consists of two adjustable steel pins, attached to the fulcrum lever, Q, and turned conical where they fit in the socket, D. The fulcrum lever is pivoted on a pin, R, fixed in the framing of the machine, and is connected at its lower extremity to the nut, S, in gear with the regulating screw, T. The to-and-fro movement of the fulcrum lever, Q, by which heavy or light blows are given by the hammer, is placed under the control of the foot of the workman, in the following manner: U is a double-ended forked lever, pivoted in the center, and having one end embracing the starting pedal, P, and the other end the small belt which connects the fast pulley on the driving shaft, A, with the loose pulley, V, or the reversing pulleys, W and X. These are respectivly connected with the bevel wheels, W_{1}, and X_{1}, gearing into and placed at opposite sides of the bevel wheel, Z, on the regulating screw in connection with the fulcrum lever. When the workman places his foot on the pedal, P, to start the hammer, he finds his foot within the fork of the lever, U; and by slightly turning his foot round on his heel he can readily move the forked lever to right or left, so shifting the small belt on to either of the reversing pulleys, W or X, and causing the regulating screw, T, to revolve in either direction. The fulcrum lever is thus caused to move forward or backward, to give light or heavy blows. By moving the forked lever into mid position, the small belt is shifted into its usual place on the loose pulley, V, and the fulcrum remains at rest. To fix the lightest and heaviest blow required for each kind of work, adjustable stops are provided, and are mounted on a rod, Y, connected to an arm of the forked lever. When the nut of the regulating screw comes in contact with either of the stops, the forked lever is forced into mid position, in spite of the pressure of the foot of the workman, and thus further movement of the fulcrum lever, in the direction which it was taking, is prevented. The movable fulcrum can also be adjusted by hand to any required blow, when the hammer is stopped, by means of a handle in connection with the regulating screw.

In conclusion the author wishes to direct attention to the fact, that in many of our largest manufactories, particularly in the midland counties, foot and hand labor for forging and stamping is still employed to an enormous extent. Hundreds of "Olivers," with hammers up to 60 lb. in weight, are laboriously put in motion by the foot of the workman, at a speed averaging fifty blows per minute; while large numbers of stamps, worked by hand and foot, and weighing up to 120 lb., are also employed. The low first cost of the foot hammers and stamps, combined with the system of piece work, and the desire of manufacturers to keep their methods of working secret, have no doubt much to do with the small amount of progress that has been made; although in a few cases competition, particularly with the United States of America, has forced the manufacturer to throw the Oliver and hand-stamp aside, and to employ steam power hammers and stamps. The writer believes that in connection with forging and stamping processes there is still a wide and profitable field for the ingenuity and capital of engineers, who choose to occupy themselves with this minor, but not the less useful, branch of mechanics.

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THE BICHEROUX SYSTEM OF FURNACES APPLIED TO THE PUDDLING OF IRON.

Since the year 1872, the large iron works at Ougrée, near Liege, have applied the Bicheroux system of furnaces to heating, and, since the year 1877, to puddling. The results that have been obtained in this last-named application are so satisfactory that it appears to us to be of interest to speak of the matter in some detail.

The apparatus, which is shown in the opposite page, consists of three distinct parts: (1) a gas generator; (2) a mixing chamber into which the gases and air are drawn by the natural draught, and wherein the combustion of the gases begins; and (3) a furnace, or laboratory (not represented in the figure), wherein the combustion is nearly finished, and wherein take place the different reactions of puddling. These three parts are given dimensions that vary according to the composition of the different coals, and they may be made to use any sort of coal, even the fine and schistose kinds which would not be suitable for ordinary puddling. The gases and the air necessary for the combustion of these being brought together at different temperatures, and being drawn into the mixing chamber through the same chimney, it will be seen that the dimensions of the flues that conduct them should vary with the kind of coal used; and the manner in which the gases are brought together is not a matter of indifference.

The gas generator consists of a hopper, A, into which drops, through small apertures a, the coal piled up on the platform, D. These apertures are closed with coal or bricks. The bottom of the generator is formed of a small standing grate. The coal, on falling upon a mass in a state of ignition, distills and becomes transformed into coke, which gradually slides down over a grate to produce afterward, through its own combustion, a distillation of the coal following it. But as these are features found in all generators we will not dwell upon them.

The gases that are produced flow through a long horizontal flue, B, into a vertical conduit, E, into which there debouches at the upper part a series of small orifices, F, that conduct the air that has been heated. The gases are inflamed, and traverse the furnace c (not shown in the cut), from whence they go to the chimney. Before the air is allowed to reach the intervening chamber it is made to pass into the sole of the furnace and into the walls of the chamber, so that to the advantage of having the air heated there is joined the additional one of having those portions of the furnace cooled that cannot be heated with impunity.

The incompletely burned gases that escape from the furnace are utilized in heating the boilers of the establishment. The dimensions given these furnaces vary greatly according to the charge to be used. All the results at Ougrée have been obtained with 400 kilogramme charges, and the dimensions of the gas generators have been calculated for Six-Bonniers coal, which does not yield over 20 per cent. of gas.

The advantages of this system, which permits of expediting all the operations of puddling, are as follows:

1. A notable economy in fuel, both as regards quantity and quality.

2. Economy resulting from diminution in the waste of metal, with a consequent improvement in the quality of the products obtained.

3. Diminution in cost of repairs.

4. Less rapid wear in the grates.

5. Improvement in the conditions of the work of puddling.

As regards the first of these advantages, it may be stated that the puddling of ordinary Ougrée forge iron, which required with other furnaces 900 to 1,000 kilogrammes of coal, is now performed with less than 600 kilogrammes per ton of the iron produced. The puddling of fine grained iron which required 1,300 to 1,500 kilogrammes of coal is now done with 800. So much for quantity; as for quality the system presents also a very marked advantage in that it requires no rolling coal--the operation of the furnace being just as regular with fine coal, even that sifted through screens of 0.02 meter.

The second class of advantages naturally results from the almost complete prevention of access of cold air. The saving in wastage amounts to 3 or 4 per cent., that is to say, 100 kilogrammes of iron produced is accompanied by a loss of only 9 to 10 kilogrammes, instead of 13 to 15 as ordinarily reckoned.

The diminution in the cost of repairs is due to the fact that the furnace doors, of which there are two, permit of easy access to all parts of the sole; moreover, the coal never coming in contact with the fire-bridges, the latter last much longer than those in other styles of furnaces, and can be used for several weeks without the necessity of the least repair. The reduced wear of the grates results from the low temperature that can be used in the furnace, and the quantity of clinker that can be left therein without interfering with its operation, thus permitting of having the grates always black. These latter in no wise change, and after five months of work the square bars still preserve their sharpness of edges.

As for the improvements in the conditions of the work of puddling, it may be stated that with a uniform price per 100 kilogrammes for all the furnaces, the laborers working at the gas furnaces can earn 25 to 30 per cent. more than those working at ordinary furnaces.

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GESSNER'S CONTINUOUS CLOTH-PRESSING MACHINE.