The Iron Age 1910-03-03: Vol 85 Iss 9

THE IRON AGE New York, Thursday, March 3, 1gr1o. COMPRESSED AIR AND ITS USES.—I. Power Transmission and Vertical Excavation. Solids have considerable molecular cohesion, liquids very much less and gases none at all; their molecules tend. to separate and the application of heat increases this separating activity. Each gas has a certain ten- sion for any given temperature. By compression ten- sion is increased, following the law that action and re- action are equal, and the*tension, or resistance, of a gas is exerted equally in all directions. Air is a gaseous mixture, mostly nitrogen and oxy- gen, and behaves as other gases at all ordinary tem- peratures. It resists compression with an equal ten- sion, its tension increases when heated, and, in,common with all matter, it occupies space to the exclusion of all Fig. 1.—A Laidlaw-Dunn-Gordon other matter, 1. e., it is impenetrable so far as its actual substance goes. To these properties is due the industrial value of compressed air. Types of Compressors, The blacksmith’s bellows is perhaps the oldest type of air compressor known. The method of compression employed with the old Catalan forges is an improve- ment as it utilizes the natural fall and weight of water to trap and compress air, and there have been a number of recent applications of analogous methods. As typi- cal of these, suppose a considerable stream of water falling a moderate hight to be connected above and be- low the fall by an underground pipe or inverted siphon. The velocity of flow through the siphon will depend upon the hydraulic head or difference in level of the two bodies of water; but the maximum pressure will be determined by the vertical length of the shorter arm. If air be trapped and carried to the bottom of the siphon it will there be compressed to a tension equal to the pressure of the surrounding water. A method of collecting the air under pressure is, in effect, to in- crease the cross section of the siphon bottom and thus decrease the velocity of the flow permitting the en- trained air to separate out because of its lighter specific gravity, and from such a pocket it may be drawn as required. The trapping of the water may be accom- plished by a sucking-in process in which no doubt the head is the controlling factor.. One installation of a hydraulic compressor of this general type was said to have an efficiency of 70 per cent., the 158 hp. of the fall storing 111 hp. in compressed air. In applying steam to compress air in a cylinder by forcing in a piston it becomes the problem to unify the progressive compression in the air cylinder with the progressive rarefaction in the steam cylinder; or- dinarily with steam used expansively in a direct acting pump the steam piston would be most powerful when the air piston had least resistance, and vice versa. In one design the two cylinders were placed at right angles and the two connecting rods were pivoted to two cranks at an angle of 30 degrees apart. This Two-Stage Duplex Air Compressor. . arrangement probably partially solved the problem, and such compressors were recently said to be still in use for compressing ammonia. Another design placed the cylinders at an angle of 45 degrees and joined the two connecting rods to a single crank, which arrangement likewise met the difficulty in part. Another modifica- tion placed the cylinders at an angle of 135 degrees, but otherwise followed the last method. Apparently none of these designs fully harmonized the two pres- sures, and they proved unsteady in operation. In such machines certain parts had to be very heavy and strong, which was expensive. In lieu of the angular arrangement the straight line compressor uses a fly- wheel to store the surplus energy of the steam piston at the beginning of the stroke and deliver it at the end. In another arrangement, instead of operating a single air cylinder by a single steam cylinder, two of each kind are worked together, each set connected as in the straight line arrangement, and the two coupled together by connecting rods to two cranks placed at right angles to each other. Thus when either set is on the weak half of its stroke, the other is on the strong half of its stroke and they assist one another. The compression of air is attended with the evolu- tion of heat, which introduces another mechanical difficulty when any considerable pressure is required. Air compressed to 200 lb. from atmospheric conditions at 60 degrees F. will have a temperature between 6oo 488 THE IRON and 700 degrees F., and even much lower tempera- tures than this are troublesome. One remedy is to employ water jackets, but these are inadequate for extreme conditions, which gave rise to compressing by stages (sometimes as many as four) with cooling between, by passing the air through intercoolers. Often to cool the finally compressed air an after cooler is used, which dries the air by precipitating the con- tained moisture, making it better suited to its work, preventing freezing if the air is piped where it is ex- posed to cold temperatures. In Fig. 1 is an example of the duplex arrangement, and represents a type of compressor furnished by the Laidlaw-Dunn-Gordon Company for use on the Pan- ama Canal. The two connecting rods are seen ar- ranged a quarter revolution apart and with the fly- Fig. 2.—Diagram Showing a Method of Cooling Air During Compression by Contact with Water. wheel between them. This is a two-stage apparatus. The intercooler is at the extreme right and above the air cylinders. Formerly in the United States and at present abroad a method is employed of cooling the air during compression by actual contact with water. The gen- eral principle may be understood from Fig. 2. A piston reciprocates in a horizontal cylinder, having a vertical extension at each end, and a mass of water partly fills the whole. As the piston moves back and forth the water level rises ahead of it and falls behind it, compressing the contained air alternately at the two ends. On one stroke the inlet valve b closes and the valve d, communicating with the compressed air reser- voir, opens, while the valve c, also communicating with the reservoir, is closed by the pressure above it, and the inlet valve a opens as soon as the air below it falls to atmospheric pressure. Upon the return of the pis- ton this air drawn into the chambef is compressed, the valve a closing promptly, and c opening when the pres- sure below becomes equal or a little greater than that in the reservoir. Much of the heat of compression is absorbed by the water, which is constantly changed and its action reinforced by a spray. A second type of direct water cooling is accomplished by the use of sprays alone, which makes a large surface of water March 3, 1910 AGE available at once. This is done by introducing water jets through the cylinder heads of the air chambers to ‘play upon the on-coming piston and be broken up into spray. All water in excess of that filling the clearance space at the end of the stroke is driven into the reservoir along with the compressed air, from which it may readily be drained off. The machines in most favor in this country to-day are those cooling the compressed air by intercoolers, aftercoolers and water jackets. Such are known as dry compressors. In them a small quantity of air is left in the compression chamber at the end of the stroke, which, upon return of the piston, expands again to atmospheric pressure before any fresh air is admitted. Being warm, the amount of new air it excludes is aggravated, hence the desirability of very small clearance space. In the best designs this space is between 0.2 and 1.0 per cent. of the total cylinder volume. Compressed Air for Power Transmission, Compressed air is probably second only to electric- ity as an economic means of transmitting power con- siderable distances. There are two sources of loss— its fall of temperature in transit with corresponding loss of tension, and friction, which is believed to be partially offset by heating the air and restoring some of the lost tension. That compressed air may be trans- mitted long distances with moderate loss is shown in a 10-mile main in Paris, where there is a drop of only 16.4 lb. from an initial tension of 92 Ib. Heat, which is so undesirable during the compres- sion, is advantageous, if it can be applied to the air after transmission, for it increases the tension, and this is sometimes done in practice. The tension of compressed air at o degrees F. is half again as great at 240 degrees. It is entirely practicable to reheat to 300 degrees F., and if the temperature initially is 60 240 degrees the increase in tension amounts to ——, 240 520.6 degrees being the increase in temperature and 520.6 degrees the absolute initial temperature of 60 degrees above zero (absolute zero is 460.6 degrees F.). The conversion of mechanical energy into the ener- gy of tension is only accomplished, like other ex- changes, at a loss. The object to be gained is twofold, transmission and distribution, and conversion into a form more suitable for the purposes in hand. Com- pressed air is an admirable means by which power may be transmitted long or short distances and then distributed to small machines, whether fixed or port- able. It is also a wonderful means for the exclusion of water in engineering operations involving a con- test with water. With machines a moderately high temperature may be used, but in pneumatic engi- neering the temperature must be kept at or near nor- Pd a March 3, 1910 Fig. 4.—Sinking Piers for a Building in New York City. mal because workmen breathe it and labor in it. The reheater, then, has no place in this latter application, but the compressing and cooling apparatus have. It is important that the compressors be reliable, for a failure in the supply may mean death to workmen or at least suspension of operations. Compressed Air in Vertical Excavation, Excavation in solid, impervious rock may be ex- pensive and slow, but the penetration is very sure; but where the strata are soft or water bearing, new compli- cations enter. The actual digging and removing the soil can frequently be done with orange peel grab buck- ets or other excavators apart from the presence of workmen at the point of excavation, and the surround- ing soil may be prevented from caving in by using the open caisson. If the object is securing a footing for piers and the like, the digging may be stopped upon reaching solid rock, or if piles are to be used, they may be driven when the caisson has reached an advanta- geous depth. Concret- ing may be done through the water and the whole structure be brought up above the surface without neces- sitating the presence of workmen within the caisson, subsequent to penetration below the water level, if at all. In Fig. 3 is an example of open caisson con- struction. The piers shown were construct- ed by sinking steel caissons formed of plates to a_ suitable depth by excavating from the inside. Piles were then driven and the interior filled and capped. The illustra- tion shows a_ bridge IRON AGE 489 nears ee across the Mississippi Lis River at Clinton, Lowa, constructed, in so far foundation work went, by the Founda- tion Company of New York and Chicago for . | the Chicago and UE =m) as int i Northwestern Rail- road. It is often neces- sary or advisable, how- ever, to have workmen on the spot and to lay concrete in the dry. In securing footings for such structures as the piers of the Brook- lyn Bridge or the foundation columns of the Singer Building tower, it is well to know absolutely that the very soundest stratum has been reached and that the masonry or concrete has been laid under the best conditions. Then it is necessary to go and see the character of the rock and to have it dry for the masonry. Moreover, conditions may render the con- tinued presence of workmen almost necessary. Such considerations have brought about a great development in pneumatic excavation. Compressed air is employed in the caisson, not to perform the digging operations but to exclude water. The possibility of doing this arises from the impenetrability of air and its ability to maintain a pressure against that of water. The general principle of the pneumatic caisson is to exclude water from entrance into a bottomless working chamber by compressed air, always at a tension equal to or slightly in excess of the hydrostatic pressure of the water at that level. The tension of free air at the earth’s sur- face is equal to the weight upon it and averages at sea level 14.7 Ib. per square inch. Below the water level 1 ft. a resistance per square inch in excess of this would have to be supplied equal to the weight of a Fig. 5.—A View of the Same Work a Little Farther Along. 490 column of water 1 ft. high and 1 sq. in. in cross sec- tion. As water weighs about 62 1-3 Ib. per cubic foot, this excess tension will have to be 0.433 lb. per square inch. This, then, is the compression that will have to be effected. The tension required is 14.7 lb. more, as not only the water has to be supported but the weight of the atmosphere on the water. In compressing air, however, this one atmosphere is had to start with, so that the gauge of the compressor which shows the actual compression discloses precisely the excess. The second foot of penetration below the water level will add another 0.433 lb. of compression required, and so on. To go 50 ft. below, the air compression would have to be 21.65 Ib. per square inch, something less than 1% atmospheres. A single atmosphere is added by going to a depth of 33.94 ft. (14.7 + 0.433). Three atmospheres are about the limit of human endurance, so that the depth of 100 ft. is about as far down as it is practicable to go below the water level by pneu- matic means. If a thoroughly impervious stratum is penetrated by the pneumatic caisson the excavation may sometimes be continued further by non-pneumatic methods, leaving the caisson behind; or, if the material in the stratum is not sufficiently impervious, the cais- son may, at times, be left behind and the air pressure maintained. In the former case penetration below the three-atmosphere limit could be accomplished. A’s an example of the continuance of the air pressure subse- quent to abandonment of the caisson, may be cited cer- tain work done in sinking the foundation piers for the tower of the Singer Building. Quicksand had to be penetrated and for this the pneumatic caisson was em- ployed. Between the lowest level of the quicksand and bed rock was a thick stratum of hard pan. After going into this stratum for, say, a foot or so, the caisson was left suspended, as it were, and the ex- cavation continued on to bed rock. The air pressure was still maintained because of the permeability of the hard pan. It was sufficiently solid, however, to re- quire no lateral support, which accounts for the possi- bility of leaving the caisson. Bed rock, at the corner of Liberty street and Broadway, New York, where the Singer Building is located, is about 90 ft. below the curb and about 75 ft. below the water level. The air pressure at the finish was consequently required to be somewhat in excess of 32 or 33 lb. per square inch. Types of Caissons. The typical caisson is a very strong rectangular box without a bottom, with a cutting edge of steel around the lower edge. The sides need to be strong, since they may be exposed to the pressure of water as penetration is continued. This pressure becomes enor- mous and averages over the lateral surfaces only a little less in intensity that that of the air, when, as often happens, the air pressure within is reduced mo- mentarily and suddenly. Further, the roof of the cais- son is to be loaded with a great weight of concrete or other masonry, and while the air pressure normally assists, still the sides must be sufficiently strong to carry a heavy weight and suddenly applied. The same applies to the roof itself. The roof is perforated at one or more points by a shaft to afford communication between the interior of the caisson and the external air. Surrounding the shaft, masonry or concrete is laid. The side walls of the caisson are continued on up to inclose this material. When the caisson has reached its final level, there will thus be a shell of the same cross section as the caisson and extending from the roof to the surface or a point above the water level. Within will be a second shell, the shaft. The portion of the pier lying between the two and above the cais- son roof will be constructed in whole or in part. The space within the shaft and the working chamber are empty of solid material and have still to be filled. If the footing reached is such that the air pressure may be discontinued, this may be done and the space prop- erly filled. If the air pressure must still be maintained, THE IRON AGE March 3, 1910 the concrete may be placed in whole or in part under pressure. The office of the external shell or cofferdam is to exclude the surrounding soil and to provide a smooth surface, and thus reduce surface friction. It may also be a mold for concrete. In any particular case modifications may be made. At the very beginning of operations the caisson may have its cutting edge at or close to the surface, with the roof above that surface. The cofferdam may be constructed with a hight of a few feet and concrete added at once. It is not at all unusual to employ but a couple of sections of cofferdam. The lower one may be entirely removed while the upper one is still acting as a mold for fresh concrete. In this way it is often possible so to manage that there is never any portion 8 Quick SAND HAROPAN HARDPAN 2 e fAec?| JA Y A; wi ‘aA or TAY US a - 74 RocK Rock Fig. 6.—Vertical Sections Showing an Interesting: Piece of Work in Connection with the Singer Tower Foundation. of the cofferdam below the surface. The hardened and smooth concrete is well suited to withstand lateral pres- sure from water and soil and to set up but a moderate skin friction. In Fig. 4 is shown a view of operations in sinking piers for a New York City foundation. 3ack of the derrick on the right and seen in part be- tween its boom and post is a rectangular cofferdam only a few feet in hight. Below it may be observed the concrete of the pier, also of rectangular form, which has been previously laid and the cofferdam form removed. Concrete will be poured into the coffer- dam now in place. In Fig. 5, a later view of the same site, another cofferdam, also empty, is seen a little to the front of the former one. This view shows in the foreground, and also projecting upward from the cof- ferdam, portions of two shafts connecting undoubtedly with different working chambers. The upper end of the shaft in the one case is terminated by the air lock. In the other case no air lock has yet been attached. The pier itself is cylindrical and its concrete is in plain view with the cofferdam removed. Up and down such shafts the workmen pass. The bucket which descends empty and returns laden with spoil uses the same pas- sageway. The shafting here shown is of steel, is col- lapsible, and may be removed and used again. It can- not be removed, however, until it is no longer desired to maintain the air pressure, for it affords the means March 3, 1910 of attaching the air lock. Not only must it be hermet- ically connected with the shaft wall, but it must be securely enough attached to withstand the great up- ward thrust of the compressed air. With a compres- sion of one atmosphere, every square inch of the cross section of the air lock is thrust upward with a pres- sure of 14.7 Ib. If it is 3 ft. in diameter at the point of attachment, then the upward pressure is about 71% tons. To balance this there is only its own weight and what- ever it may contain. The shafting may be added in sections as the caisson sinks and the concrete is put on. At the close of operations the shaft lining must be removed not later than when the concreting of the working chamber is completed. The air pressure is then turned off. The entire cross section of the caisson, including the air lock, receives the upward thrust of the com- pressed air. A circular caisson 9 ft. in diameter would have an upward thrust of 67 tons. This becomes a source of real difficulty, for what is desired is a down- ward pressure on the cutting edge so as to force it down into the excavation as it is made. The weight of caisson, concrete and all the accessory structures would supply it, but it is opposed by the compressed air and also by the skin friction. In practice it is often necessary to supplement the weight by adding consid- erable quantities of pig iron. In such a job as that of the new municipal building, New York City, the capital thus tied up in the iron may run up to $25,000. Some- times the excavation has been carried some little dis- tance below the cutting edge, and upward and down- ward pressure and skin friction are so evenly balanced that some considerable additional pressure downward is needed. This is sometimes secured, in effect, by low- ering the air pressure for a moment. Thus in the case of a circular caisson of 9 ft. diameter, a reduction of 1 lb. per square inch would be equivalent to the addi- tion of % ton of pig iron. The sinking of a pneumatic caisson off shore in an exposed situation occasions special difficulties. An in- teresting case occurred in the construction of the Sa- bine Light Station, 15 miles off shore in the Gulf of Mexico, near the Louisiana and Texas line. The depth of water varies from 16 to 18 ft. Borings made showed that the bottom was practically nothing but sand to a depth of over 20 ft. The cutting edge was sunk to 39 ft. below the water level, consequently requiring an air pressure of about 17 lb. per square inch. The con- ical cylindrical caisson itself was partially erected 16 miles away and consisted of working chamber, coffer- dam and air shaft. It was built largely of cast iron plates. The shaft was of steel. At the site a tem- porary working platform was erected to envelop three- fourths of the caisson. Examination of the weather records shows that the entire sinking operation would better be done within about 40 days beginning June 1o. The erection of the caisson was begun in April and when three courses of plates had been secured in place it was launched. Previous to launching a wooden tem- porary bottom had been constructed. Subsequent to flotation this was knocked off. The number of courses of cast iron plates was increased to five and over 200 tons of concrete laid on the deck above the working chamber. To provide for giving the structure more weight quickly a wooden partition, polygonal in cross section, was constructed within the cofferdam portion and enveloping the air shaft, so that a considerable volume of water might be introduced between parti- tion and shaft. Between cofferdam and partition con- crete could also be added. The water compartment permitted a prompt sinking of the caisson to the bot- tom when once moored over the site. That excessive oscillation might be avoided before the caisson should come to rest on the bottom the annular water space was divided into sub-compartments. When the com- plex structure reached its destination a sea was run- ning, but it was decided to proceed with the operation THE IRON AGE 491 of sinking. The inlet vaives were opened, the water rushed in, and in an hour and a half the caisson was resting on the bottom. Because of its movement occa- sioned by the sea and-of the character of the bottom, the caisson came to rest with a penetration into the sand equal to the hight of the working chamber. Around the exterior of the caisson 200 tons of rock was placed. The air lock was attached, air turned on and actual excavation begun, and in about a month this was completed and the caisson had reached the desired level. The diameter of the cutting edge was about 35 ft. For a hight of about 13 ft. the caisson tapered in slightly and the remainder was cylindrical. The Air Lock, The object of an air lock is similar to that of a canal lock. The latter permits passage between differ- ing levels; the former passage between atmospheres of differing tensions. The working chamber of a pneu- matic caisson and any connecting passages must be absolutely closed, otherwise the compressed air will promptly escape and possible disaster result. But it is imperative to get in and out. As may be seen in Fig. 6, the air lock is a chamber with a down opening door in the floor and one in the roof. Suppose the upper door to be closed and the cock connecting the lock chamber with the outside air shut. If a connec- tion between the shaft and the lock chamber be opened the tensions above and below the lower door will be equalized, permitting that door to be opened. Passage into or out of the lock chamber may then be made. The lower door may be closed and the cock shut off which controls the connection between shaft and lock, and by opening the connection between the lock and the outside atmosphere entrance into or departure from the air lock may be made. Since whenever the lock cham- ber is connected with the outside air it is shut off from the shaft and whenever cut off from the outside air it is connected with the shaft, it is possible to manage these operations by a single three-way cock. New York Conditions, While the pneumatic caisson is frequently used in bridge construction, its use in the construction of the foundations for skyscrapers has been a development comparatively recent, because the very tall building itself was only recently in demand and geographically limited, because ordinarily conditions can be more economically met by other methods on the southern part of Manhattan, especially in the financial and office district, conditions and demand are such that com- pressed air seems almost the only means available. From about the Wanamaker store northward bed rock is just below the curb or even above it, but southward the stratum of solid rock dips below the street level until a depth of 183 ft. is reached at Broadway and Duane street. It rises again and approaches the street surface in the vicinity of the Battery. Nearly the whole is beneath the level of mean high water. As there are great deposits of sand overlying the rock in this same district, a solid foundation is frequently to be reached only by passing through quicksand. At times the depth of the subaqueous penetration is con- siderable. As before noted, there was about 75 ft. of such work at the Singer Building. At the site of the building of the Trust Company of America, on Wall street, near Broad, the layer of quicksand varied, so it is said, from 15 to 45 ft., and this was underlaid by a stratum of hardpan 3 to 5 ft. thick.* Laying bare bed rock without damage to nearby buildings and doing it all within a confined area means that other things besides mere cost of the work itself must be considered. If the adjoining buildings have been erected, not on the rock but upon spread footings underlaid by quicksand, nothing may be done that will withdraw any of this underlying material. Otherwise account of the foundation *A detailed operations in as : this building were given in The Iron Age Yooreasy aS a NE 492 THE IRON AGE sheet piling might be driven around the site and the interior of the cofferdam thus constructed excavated and pumped out; but if the piling is not sufficiently tight, sand might be pumped away from the exterior and provoke settlement of the adjacent structures. It is probable, however, that practically impervious piling could be driven. Geo. W. Jackson constructed a coffer- dam in 30 ft. of water with steel sheet piling. The piling must be braced, however, to withstand the lateral thrust occasioned by the hydraulic head plus the effective weight of the superimposed soil and building. It seems possible that this could be accomplished. But whether the expense might not fully equal the pneu- matic method is another question. At any rate, the pneumatic caisson is almost exclusively used in New York City where the conditions are such as those de- scribed. It was intended originally to sink the piers for the Singer tower only to compact hardpan, which overlies the rock to a considerable hight. One of the pier caissons had been so built when it was determined to carry the remaining piers to the bed rock itself; then, that the first pier might be no exception, the con- tractor, the Foundation Company, undertook to com- plete this one, not by letting it down until its foot rested upon the rock, but by going beneath it and filling in the intervening distance with concrete. In Fig. 6 is a vertical section through three of the piers, the one in the center being the short pier in question. To the right is a finished pier. The caisson minus its deck is left hanging at a point where it had just begun to enter hard pan. The collapsible steel shafting has been removed, tie rods introduced and the whole con- creted up from bed rock to the top. On the left is an unfinished pier. The air lock and steel shafting are still attached and the air is still on. The air is supplied not to the lock or shafting directly, but to the caisson or working chamber. The excavation has been continued to bed rock. Instead of concreting up the base of the pier, the excavation is continued off to the side to get below the short pier. This pier was of very great weight. The skin friction was no doubt very consid- erable, but it was not deemed advisable to rely on this to support it, so in undermining the work was done in sections, leaving at all times a support of hard pan, hard concrete or both. The entire excavation was always under air pressure. Mine Shaft Sinking. It is sometimes possible to employ both open and pneumatic methods in sinking caissons. If the material first encountered is non-water bearing, the caisson may be sunk partially or entirely through it without com- pressed air. If the underlying material is under con- siderable upward pressure, the floor of the excavation may be rent open when the overlying support has been considerably reduced. This upward thrust is usually oc- casioned by the presence of water or quicksand under the pressure of some superior hydrostatic head or of some weight of material, but if nothing of this kind is to be feared, open excavation can proceed until the water itself is encountered. Thus expense may some- times be reduced. At other times, in ordinary engi- neering operations, the open method may be employed throughout, especially if the water level is reducible by pumping. Frequently in Germany, and occasion- ally here, in sinking mining shafts to the ore ledge a considerable flow of water is encountered. The steel sheet piling formed of channel bars held face to face and interlocked with I-beams was invented to care for a water-bearing stratum in sinking a shaft at the Good Hope mines in Germany. At first the attempt was made to sink a cylindrical shell of masonry. Be- fore the water bearing stratum was quite penetrated and the underlying clay reached, the shell stuck, having gotten out of plumb. Metal piling of the kind de- scribed was successfully employed, a satisfactory joint being made with the masonry. March 3, 1910 Sometime since the Cleveland-Cliffs Iron Mining Company proposed to sink a shaft to the underlying rock ledge. Water was known to underlie the sur- face, but in what quantity was uncertain. A number of perforated tubes were put down and some connected up with pumps. The pumps were started and the level of the water watched in an unconnected observation pipe. It was found that control of the water by pumps could not be relied on. The Foundation Company be- ing engaged to sink the shaft proceeded to do it by pneumatic methods. The shaft was to have an inter- nal section of about 11 x 15 ft., and to be of reinforced concrete. A cutting edge was first constructed of heavy timbers, with a steel shoe. Upon this a wall of reinforced concrete 3 ft. thick and of the required internal cross section was built. At the hight of about 6 ft. a circumferential notch was arranged on the in- side for securing the roof of the working chamber to the concrete shell. A steel shaft 4 ft. in diameter was secured to the roof and provided with a Moran air lock. With the concrete shell about 18 ft. high opera- tions were begun without the use of compressed air, but as the water level was but 5 ft. down it was not long until it was brought into service. The concrete was continually kept 18 ft., or thereabouts, above the surface, and thus required the use of three sections of forms. Considerable space was left upon the inside of the concrete shell between it and the shaft. Eventually the whole interior was to be free, so that no additional concrete could be laid to provide a sinking weight. However, none was required until a depth of 35 ft. below the water level was reached. The upward thrust of the air was now about 430 tons. It is probable that penetration thus far had been materially assisted by the 18 ft. of concrete shell above the surface of the ground. Wet sand was now put on to give additional weight. When at last the ledge was reached it was found to be not at all horizontal. The surface was leveled and sinking continued for a couple of feet fur- ther. This penetration into the rock was for the pur- pose of passing a seam and making a secure interlock. The blasting was performed under air pressure. A part of the timbering of the cutting edge was removed, leaving projecting bolts. When the bottom of the con- crete shell was now joined to the rock by a stratum of concrete, these served to bind the two masses of concrete together. A similar bond was made with the rock by steel dowels. After this concrete had been put in the air pressure was kept on for several days to prevent its injury by the pressure of the external water. (To be continued.) —_— So Railroad Equipment Orders.—The Chesapeake & Ohio is receiving bids on 1500 cars. The Chicago Great Western is reported in the market for 200 steel underframe box cars and the Mexico Northwestern for 260 freight cars. The Hill lines are reported in the Railway Age Gazette to have ordered 4000 freight cars from the Haskell & Barker Car Company—3500 box and 500 automobile cars. Of the former, the Burling- ton road will get 1500. The Rock Island has ordered &25 steel underframe box cars from the Western Steel Car & Mfg. Company, and is still in the market for 775 cars. The Richmond, Fredericksburg & Potomac is reported to be inquiring for 20 locomotives, and the Colorado & Southern for 15, in addition to 7 for the Fort Worth & Denver City. The Hocking Valley has ordered 10 locomotives, and the New York, Ontario & Western 6, from the American Locomotive Com- pany. wa Commenting on the weekly trade reviews of the commercial agencies, a financial writer on an im- portant daily says they have “ found nothing absolute- ly bad to report.” This is quite reassuring. March 3, 1910 The Woods No, 20 Planer and Matcher. The rapid production and high degree of finish de- manded by the modern car shop and planing mill has resulted in the very rapid development of the planing machine. Perfect cutterhead work and rapid feed have made necessary some radical changes in design which are well exemplified in the machine shown in the illus- trations, built by the S. A. Woods Machine Company, Boston, Mass. Figs. 1 and 2 show the front and rear of the machine and give a general idea of its appear- ance. Notable features are the use of one belt, which drives both cutterheads, a design made possible by a new type of flexible coupling, illustrated in Fig. 3, and the location of the belt on the back of the machine which tends toward much greater security against acci- dent to the operator. The workman is required to true the cutterheads while they are running at full speed, and it will easily be seen that the removal of the belts from the front of the machine is a safeguard of no small importance. One of the obstacles to securing high class cutter- head work is the difficulty of maintaining the journals in perfect condition. The pull of their belts under the cutting strain may be as high as 1500 lb., and the speed 3200 ft. per minute. Under these conditions, with the increased size of belt required for fast feed, the accu- racy of the adjustment of the cutterhead is soon lost by Fig. 1.—The New Rapid Production Wood ee Fig. 2.—View of the Opposite Side of the Planer, the wear on the journals, as adequate lubrication of long boxes is difficult and uncertain. The vibrations and jars of the cutterhead caused by the belts on the THE IRON AGE Planer Built by the Showing the Single-Belt Drive 3.—Detail Showing the Flexible Couplings Connecting the Pulley Shafts to the Cutterheads, lig. shaft is another weakness which is considered to be serious and difficult to eliminate. It has not been un- usual for the belt lacing to leave a mark on the stock each time that it went over the pulley. The difficulty } 8S. A. Woods Machine Company, Boston, Mass. of making two belts run exactly alike has also added to the troubles of the de- signer under the for- mer standard prac- tice. The impor- tance of the factor of belt slip in the prob- lem will be appre- ciated when it is realized that a differ- ence of 0.01 in. in the diameter of the cut- terhead pulleys means a difference from 10 to 12 ft. in the amount of belt travel at the ordinary pla- ning mill speed, the difference being ex- aggerated by varia- tions in thickness and tension of belts. In this new machine the designers have sought to overcome all these objectionable features by employing 494 THE IRON AGE a single belt which passes over the driving pulley of each cutterhead shaft. Each pulley is supported by boxes entirely independent of the cutterhead itself, the connection being made by a flexible coupling. The de- signers believe that this coupling absorbs effectually all the vibrations transmitted to the pulley by the belting, which relieves the cutterhead journals from the strain of the belts and other disturbing elements. The use of very short journals upon the cutterheads is also per- mitted, thus simplifying the problem of lubrication, which is accomplished by improved oiling devices. The design also makes possible the instant detaching of the cutterhead from the spindle, leaving it free to be turned when setting up without disturbing the belts. High speed steel cutters are used on this machine, which as- sist in the production of finished surfaces, upon which little or no trace of tool marks can be found. Sn The Kern 25-In. High Speed Dri''. A combined drilling and tapping machine designed to use high speed steel tools has been perfected and Two Views of the 25-In. High Speed Drill Built by recently placed on the market by the Kern Machine Tool Company, 4657 Spring Grove avenue, Cincinnati, Ohio. This drill is known as the 25-in. high speed up- right drill, and is equipped with a three-step cone pulley and double back gears. All the features that have been found, from experience, to be essential to the rapid production of accurately drilled and tapped work have been retained and several new ones have been added. Principally of interest are the details of the back gear arrangement and the positive feed mechanism. Nine changes of spindle speed are provided; three are direct or open belt speeds, and these are tripled by the double back gears. The belts run at high speed and afford ample power for high speed drilling, while for slow speed drilling and heavy tapping this high initial power is increased by the great speed reduction March 3, 1910 obtained through the back gears. Advantages, as com- pared with the usual four-step cone pulley type drill with single back gear, are one more speed and greater driving power, for the three-step cone pulley can take a wider belt and it also has larger diameter steps. The cone diameters are 9, II and 13 in., respectively, and a 3'%-in. double belt driven at 440 rev. per min. is used. With the four-step cone drive usually employed, the diameters vary from about 5 to 11 in. and a 2%-in. sin- gle ply belt, seldom running faster than 350 rev. per min. is used. Hence the claim that this drill has about twice the power of the ordinary type for high speeds and three times for slow ones. The powerful double back gears are located on the top housing between the spindle and the frictions used for starting, stopping and reversing it. Sliding gears and a positive clutch provide for the necessary changes- in the back gears, and by a conveniently located lever - on the top housing these changes may be effected with- out stopping the machine. The highest gear ratio is 12.5 to 1, and the frictions of the controlling clutch have the benefit of this high ratio. In severe drilling the Kern Machine Tool Company, Cincinnati, Ohio. and tapping operations, they are, therefore, required to pull less than one-twelfth of the actual power ex- erted at the spindle, and at all times have a compara- tively light duty to perform, which obviates likelihood of slipping and insures long life to the clutches. On the top housing between the driving cones and the double back gears is located the tapping attachment operated through spur gears and clutches by a lever projecting from the side of the column. This lever controls the starting, stopping and reversing of the spindle, and when it is in its neutral position the entire machine, with the exception of the cone pulleys, is brought to a standstill. This not only eliminates un- necessary wear, but also furnishes a convenient means for making the changes in the back gears without any shock to the drill. On machines where no tapping at- March 3, 1910 tachment is provided this clutch and the lever are still furnished for controlling the starting and stopping of the drill. The positive geared feed which provides eight dif- ferent rates, advancing in approximately geometrical progression from 0.006 to 0.050 in. per revolution of the spindle, is mounted on the sliding head. The con- struction is very simple, and only seven gears and two levers are used. The correct position of the levers for any desired feed is indicated by a feed plate fixed to the drill. The principal dimensions and specifications of the drill are given in the following table: ee OE OI WB eas Oi OE a RA a ei ees SO Diantabes. of eerie. Teele iis a: 56 <a.0 0 win 2 04.00.00 o ee 6Y, ee eS RR eee eer yee errr rc Ce 1°/16 Diameter of spindle in sleeve, inches.................. 1" /is Greatest distance from spindle to table, inches.......... 32 Dea Pel: CE SN. Ts oe 0-5 5c aes 0s aia aes 10 ee IID oak a da 600 65d od os 6 akon eens No. 4 pumeee Ga GEO, GUNG ccc ak shi abed wes tows eee 2% Diameter of driving pulleys, inches..................4:5 14 Face.of Grivimng palleya, WeRAR. oo icnc icaddiees ces enon 4% PrMubater. GCE TAN CO yo 6 ok SA WIN es Sb RSE eC 23% Speed of countershaft, revolutions per minute.......... 445 Vertical adjustment of table, inches.................6. 15 ot: wee; CORR 6 oe ons sas 6d aes seuntetkaw baledes 1,900 All the gears employed are of steel, and have wide faces and coarse pitch. An automatic stop and depth gauge are provided which operate by graduations on the spindle sleeve and permit the spindle to trip at any desired point within the limits of its travel, thus allow- ing any number of holes to be drilled to a fixed depth. In designing this machine care has been taken to locate all the controlling devices at convenient points. It will he noticed from the illustrations that all the levers are placed on the right side of the drill, and may be man- ipulated by the operator without any change of position. po ___ The New Brown & Sharpe Toolmakers’ Vise The toolmakers’ vise shown in the illustration is the latest addition to the line of tools made by the srown & Sharpe Mfg. Company, Providence, R. I. It is of steel, drop forged and case hardened, and, while light and convenient to handle, is strong enough to stand any severe usage to which it may be sub- It is particularly useful in connection with jected. A New Vise for Toolmakers, Made by the Brown & Sharpe Mfg Company, Providence, R. I. drilling, fitting and laying out work on _ surface plates, as well as for general use in machine shops. Two jaws, giving a maximum capacity of 2 in., slip on and off the end of the screw and can be used in- terchangeably. The screw is turned by a short slid- ing bar fastened through a knurled nut at the end, the nut affording a firm grip for the operator when tight- ening the jaws. The screw is hardened to resist wear. An accurate V-block placed in the base of the vise adds much to the value of the tool, permitting its use for centering round bars and for other pur- poses requiring a block of this character. It is used by simply turning the vise upside down. THE IRON AGE 495 The Baird Wire Forming, Ferruling and Stamp- ing Machine. A new, machine of the Baird Machine Company, Oakville, Conn., is shown in Fig. 1. It is designed to combine in one the wire forming and stamping ma- chine and the wire forming and ferruling machine, which were illustrated and described in The Jron Age Fig. 1—A Combination Machine Built by the Baird Machine Company, Oakville, Conn., for Forming, Stamping and Ferruling Small Wire Articles, January 6 and February 3, 1910, respectively. Like these it is automatic in operation and will take the wire from the coil, straighten, feed, cut off, form and stamp it into small articles, and take sheet metal from a reel carried on the vertical board shown at the right of the machine, cut off, form and attach a ferrule made from it around the wire form and then carry it to a press and flatten or stamp it, as shown in Jig. 2. Originally this machine, like the other two men- tioned, was a special one made for hose supporter loop Fig. 2.—Typical Products of the Machine. manufacturers, but many other different lines have been found for it, so that it is now built as a standard machine., The completed articles are turned out at the rate of approximately 60 to 80 per min., according to size and shape, and no attention is necessary from the operator beyond keeping the machine supplied with wire and metal strips, and removing the finished prod- uct from time to time. Several sizes of the machine are built to cover a large range of work. —__~+e—____ The price of silver has fallen sharply on the an- nouncement of an advance in the duty imposed by India. The new duty is to be 4 annas per Troy ounce. The value of an anna is about 3 cents. The Treasury Department has extended the benefit of the drawback to finished safe doors, exported as a part of safes or separately, manufactured by the Ely- Norris Safe Company of Perth Amboy, N. J., with the use of imported steel castings. 496 THE IRON AGE March 3, 1910 Segregation Phenomena in Steel Castings. Results of Recent Metallographic Investigations ;in a Comparatively Unworked Field. BY S&S. S. Some 14 years ago the subject of segregation nomena in cast iron was quite thoroughly inves by the writer. phe- ited that tige The results which he publishe d at time were somewhat unsatisfactory, owing to the fact that in cast iron the amount of free carbon present is a factor which not only greatly hampers observation D-11off Center Ee — Fos B- A-At G — | 'X= Percentage Segregation ‘ 9! x ” ” Gate — Cold Poured Ingot 160 a10| -071 | .051 |.052 a P.- 088) O74, 03 oan | 020 840% a. 74 1.71 8 08 |-61 (2184 .50 |.50 ley 21 |.21 asd -98 |.48 |.38 24 | 47 108¢ Fig. 1 in Cold Poured Casting. mechanically, but is of no small importance in affect- ing the results themselves. In steel which has under- gone werk the observation of segregation phenomena could not possibly give as satisfactory results as in ingots or castings which have had no work done upon them, because the soaking, rolling or hammering all tend more or Jess to counteract the effect of segrega- tion, both mechanically and chemically. The steel which is cast in sand molds has long been looked upon ¢ ae /D-11off Center X c-0"” J yo ; 1 ~B-2” ” —A-At .G-At Gate |X=Percentage Segregation | Hot Poured Ingot A'B\/C|}/D|G|X Si. |.45 |.42 |.46 |.38 |.3 4 \a240 8. 4 47,100,058 |,047) 052/183 22} P. .088 | 057 040,082 080 198% 4 Mn. 81 re 76 “i 61 me Cs \,a2 | 46 32 22 \.21 [148% lesa \.27 Fig. 2.—Segregation in Hct Poured Casting. as more or less of an uncertainty for the purpose for which it is intended, unless very large factors of safety are allowed, because it is almost impossible to get castings which are homogeneous. This lack of homogenity comes about primarily from the occlusion of certain gases or foreign substances, such as dirt or *A paper read at the yoesting of the Philadelphia Foundry- men’s Association, March 2, 1910 KNIGHT. slag, in the material itself while in a semimolten or plastic condition, as well as from segregation. ** Killing *? Basic Steel for Castings. The “killing” of steel, as it is popularly termed, is unquestionably one of the hardest things to accom- plish satisfactorily in the steel foundry. tice is being used the fact that molten metal the ladle a all forming elements, human possibility, your steel during position. lf basic prac- you have covering the hungry for beyond to keep chemical com- basic heats, run- ing from 50 to 100 tons, poured from a single ladle, where the silicon content varied 400 to 500 per cent. in samples taken from the first and the last of the pouring, and yet the total amount of time in the operation was less than half an hour. casting plants the metal is which is that it now known, same In slag Cs acid means is is the has seen many far pouring of The writer as as consumed In some tapped into a receiving Fig. 3.—Iron Sulphide Crystals in Refined Iron. ladle mounted upon trunnions, and