Casting Iron Segments for New York Tunnels

A Tonnage Job on Which Large Output is Demanded and the Work is Facilitated by the Use of Jar-Ramming Molding Machines

By E C Kreutzberg

Published in The Foundry, Vol 44, Cleveland Ohio, April 1916, P. 217

The manufacture of gray iron castings for use in the construction of tunnels has developed in the last decade into an exceedingly important branch of the foundry industry. During that time several hundred thousand tons of pig iron have been converted into tunnel castings and, owing to the remarkable manner in which these subaqueous highways have filled the need for rapid transit facilities between New York and the surrounding territory, it is to be expected that the demand for such castings in the future will keep pace with the requirements of congested centers of population where waterways are an obstruction to traffic. A sub-aqueous tunnel driven by the shield method, although its construction calls for engineering ability of the highest order and the working out of a tremendous amount of detail may be described briefly as a cast iron tube, encased in a grouting of cement, and lined with concrete. The tunnel is constructed along a path opened by a steel shield; the latter is advanced by hydraulic jacks and is provided with a door through which workmen pass the dirt that they remove from in front of the shield. These men work under a hood, and in atmosphere which is maintained under pressure to reduce to a minimum the leakage from the riverbed above. The cast iron tube is built up of rings, which have a length of about 2 feet along the axis of the tunnel, and a diameter which generally varies from 17 to 20 feet, depending on the size of the tunnel. The rings, in order that they may he handled with facility, are built up of segments, of which there generally are 9 to 11 to a ring, depending on the diameter. The segments are provided with holes through which the casing to cement grouting may he applied from the interior of the tunnel, and with flanges for bolting them together, the joints being calked. After the completion of the tube, the tunnel is equipped with railroad tracks of piping, according to the purpose for which it is designed.

The primary requirements of a foundry engaging in the manufacture of tunnel castings are a large molding floor area and a corresponding melting capacity, since the molds are of good size and the castings are heavy and thousands of them are needed to keep abreast of the requirements of tunnel construction. Although the methods of molding are simple, numerous flasks and other special equipment are needed, while for machining the segments much special machinery of unusually large size and capacity must be installed. In fact, such work calls for specializing by the foundry participating in it to a degree unusual in jobbing work. As a result, only a few concerns have engaged in the manufacture of cast iron tunnel segments. Among them is the Davies & Thomas Co., Catasauqua, Pa, one of the first concerns to embark in the manufacture of such castings, and manufacturer of the greater portion of the cast iron tonnage embodied in the sub-aqueous tunnels under New York harbor. At the present time, this company has two unfinished contracts for tunnel segments, one involving 18.000 and the other 22,000 tons, of which approximately 30,000 tons still are to be produced. The routine worked out at this plant in the manufacture of these castings is of interest to every foundryman.

Fig. 1 Direct-Draw, Rollover, Jolt Machine Used for Making Drags of Tunnel Segment Molds

Fig. 2 Tunnel Segment Pattern and Follow-Board and Drag Section of Flask

Fig. 3 Cope Molding Machine for Tunnel Segment Castings

Fig. 4 Completed Cope and Drag, Showing Type of Cores Used for Providing Bolt-Holes

Will Increase Output

At the present time the Davies & Thomas Co. is devoting 14 molding floors to tunnel segment castings, each floor producing 12 to 14 segments a day, resulting in a daily output of approximately 125 tons. Plans now are being prepared to increase the output and it is expected that by Sept. 1 the production will be about 175 tons per day. The molding methods employed are principally of the well-known floor type, as illustrated in Figs. 2 and 4. The pattern, shown in Fig. 2 is of simple construction and is mounted on an ordinary wood follow-board. The flasks are cast iron and are provided with trunnions which admit of convenient handling by the hoists which serve each floor. The bottom of the cope is convex and the top of the drag concave, thus providing a joint which conforms to the contour of the pattern; the mold is located entirely in the drag, the cope serving simply as a cover. The casting is poured through two gates, located at one end of the flask and the mold is provided with a riser. Figs. 2 and 4 illustrate the sequence of molding operations: The drag is rammed and rolled over, the cope is rammed and lifted, the pattern removed, the cores set in the prints and the mold closed. These castings are made on a piecework basis, one molder and one or two helpers to a floor, the molders engaging their helpers.

On account of the large floor space at the company's command, and the correspondingly great output which it thus has been able to obtain by floor molding methods, it is only within the past few months that it has undertaken the installation of molding machines for use in producing tunnel segment castings. The two machines in use were furnished by the Osborn Mfg. Co., Cleveland. The one shown in Fig. 1 is a direct-draw, roll-over jolt, used in molding the drags, while the cope machine, illustrated in Fig. 3, is of the plain jar-ramming type. Both machines are manipulated by compressed air. The flasks used for machine molding, as shown in Fig. 3, are exactly file same as those used for floor molding. For removing the drags, the roll-over machine is served by a receiving car, from which the drags may be transferred by crane to the pouring floor. The copes, which do not include any portion of the mold and whose function is simply to close the drags, are lifted off the plain jolt machine by a crane which carries them to the pouring floor. Molding sand is supplied to the machine by gravity, flowing into the flasks from an overhead steel reservoir which has capacity for holding 45 tons. The downtakes from the reservoir are provided with gates by which the flow of sand may be regulated from the floor. The supply of sand in the reservoir is replenished constantly by a bucket elevator which is fed from a pit in the foundry floor. The molding machine installation has a capacity for turning out a complete mold every five or six minutes; it has not yet been put in full operation due to the fact that facilities for handling the output of the machines have not been completed. The company is arranging for the addition of a traveling crane and other equipment necessary for this purpose.

For each segment mold 15 dry sand cores are required to form the bolt holes in the flanges, and the tap hole in the face of the casting. These are placed in the molds in prints which are made by removable lugs on the pattern. The bolt hole cores are made in large numbers, the output ranging from three to four tons a day. As shown it in Fig. 4, they are of two sizes, the bolt holes at the end of each segment being formed by a single large core, while each of the side bolt holes is formed by a small core. A portion of the output of the large cores is turned out by the usual hand method at a rate of 55 to 60 cores per day per man; the remainder of the end cores and all of the small bolt hole cores are produced on roll-over machines of the type manufactured by the Osborn Mfg. Co., Cleveland. Three of these machines have been installed, one being devoted to end cores and the remaining two to side cores. The Machine production of end cores is about 100 per day, while the side core output for each machine is approximately 1,800 per day. The side cores are made in batches of eight. The core department is equipped with three large coal-burning ovens and the entire floor space is commanded by a 6-ton traveling crane.

Fig. 5 Machining Sides of Segment Castings on Larger Milling Machine

No. 2 Plain Pig Iron Used

The specifications to which the segments must conform were drawn by the public service commission, first district of the state of New York. These specify the use of No. 2 plain pig iron, and for the usual physical requirements in the resulting castings. The plant is equipped with four cupolas, three of which have capacity for melting 12 tons an hour each, while the fourth has an output of 10 tons an hour. At the present two 12-ton cupolas are operated and the third shortly will be employed. The foundry is provided with a network of narrow-gage industrial track which is utilized for distributing the metal in ladle cars. Approximately 24,000 square feet of foundry floor space is devoted to the segments.

Between the foundry and machine shops is the cleaning department, 40 x 80 feet. A branch of the industrial railroad which communicates with all parts of the plant extends into the cleaning department and is equipped with three 6-ton overhead traveling cranes. In this department the castings are cleaned superficially in order that they may be handled with facility in the machine shop: they are subjected to a more thorough cleaning and finishing press after they have been machined.

The castings are delivered to the cleaning room as soon as they have been shaken-out, and after cleaning they are coated with tar while still hot. The castings which cannot be tarred immediately are placed in a pit in which they retain their heat until it is convenient to coat them. The machining of tunnel segment castings is an exacting operation, since any inaccuracies may result in serious deflections in the work of tunnel construction. The segments now being made at the Davies & Thomas plant are designed for assembling into rings, 18 feet in diameter and 26 inches wide, nine segments and one key constituting a ring. Of these segments, seven are provided with joints whose planes pass through the center of the ring. The remaining two have one tapered joint each, thus forming an opening into which the key segment may be inserted from the interior of the ring. The key segments weigh about 400 pounds each, while the weight of the other segments is approximately 1,500 pounds each. The key segments arc molded in the same manner as the heavier segments, but the flasks are shorter and not so many cores are required. The thickness of the metal in these castings averages 1-1/4 to l-5/8 inches. For performing the necessary machine shop operations, the Davies & Thomas Co. has installed heavy machinery which is located in two buildings, 55 x 160 and 55 x 110 feet, respectively. For machining the sides, the heavier segments are placed two-high, on two 42-foot Ingersoll milling machines. Each of these machines is driven by a 50-horsepower, direct-connected motor and is provided with two tables, one of which may be loaded while the castings on the other are being chucked. The machines, known as hoggers, mill both sides of the segments simultaneously, completing two segments every 15 to 20 minutes. As shown in Fig. 5, the segments arc held in a chuck, patented by the Davies and Thomas Co., which was designed especially for this work.

Fig 6. Machining Tapered Ends of Segments on Large Planer with Milling Cutters

Fig. 7 Machining Key Segments on a Milling Machine

Machining The Tapered Ends

For machining the tapered end, the segments are placed on planers which are provided with two milling heads each so that both ends may be machined simultaneously. Three planers are engaged in this work, each of which has a length of 62 feet in the shears. These planers have two tables each, thus permitting one to be loaded while the other is under the milling cutters. A special method of driving, involving the use of a wheel and disc friction and a worm gear, has been applied to these planers in order that the feed of the tools may be adjusted to keep pace with the capacity of the milling cutters as well as to permit rapid forward and return movements when desired. Each planer table has a capacity for holding six to eight segments and the operating time for milling the ends averages about one hour per table. In addition, a 95-foot planer, shown in Fig. 6, like the 42-foot milling machines, is devoted to the milling of sides. This planer also is provided with two tables, each of which has a capacity for six segments, the machining time per table being about one hour. It is equipped with the same special drive which has been applied to the planers engaged in milling ends. For milling the key segments, a third Ingersoll milling machine, shown in Fig. 7, is employed. This is equipped for milling both the ends and sides of the key segments. For milling the ends, the table has a capacity of seven segments, while for milling the sides, the capacity is five.

Fig. 8 Machining a 3/4 inch Taper on a Ring which is to be Used in a Curved Section of the Tunnel

Rings which are intended for use in curved sections of tunnels are assembled and machined on a boring mill which has a 19-foot table, but which can take work 25 Feet in diameter. The rings are held in a chuck which elevates one side, usually about 1/4-inch above the level of the other, so that after the two sides have been machined, they converge slightly, instead of being parallel to each other as in the case of rings designed for straight sections of the tunnel. A view of the boring mill in operation is shown in Fig, 8. Only one side of the ring is tapered on the boring mill, the other sides of tire segments forming the ring being machined separately on milling machines. The boring mill is served by a 6-ton traveling crane. Each milling machine and planer is commanded by a 3-ton traveling crane. The machine shop is equipped with two Ingersoll milling cutter grinders which are constantly operated, due to the severe service to which the milling cutters, both on the planers and milling machines, are subjected. In addition to the foregoing equipment, which is used exclusively for work on tunnel castings, the company operates a large machine shop, 50 x 150 feet, devoted to general jobbing work.

Fig. 9 Shipping Department, Where Castings are Finished and Inspected Prior to Loading Them on Cars

Fig. 9 shows the finishing, inspection and shipping department, which is 30 x 150 feet and is commanded by a 15-ton overhead traveling crane. Here all burrs and imperfections are removed, the bolt holes are drifted to remove obstructions, and the holes in the surfaces of the segments, which are to be used in encasing the tunnel in a grouting of cement, are reamed and tapped, all of these operations being performed by pneumatic tools. The inspection of the castings is in charge of a representative of the public service commission of the first district of the state of New York. He examines the castings for all possible flaws, employing templates to test the accuracy of the joints and the spacing of the bolt holes. Prior to shipping the machined surfaces of the castings are coated with grease to prevent rusting.

Large Orders for Segments

In addition to operating what is one of the largest jobbing foundries in the country, with a capacity for melting 250 tons of gray iron daily, the Davies & Thomas Co. enjoys the distinction of having supplied the major portion of the cast iron linings for sub-aqueous tunnels driven by the shield method in this country. The contracts on which it now is working involve l8,000 tons of segments for the Rapid Transit railroad tunnel, which is under construction from Old Slip, East River, Manhattan, to Clark Street to Fulton Street, Brooklyn, and 22,000 tons for the Eastern Rapid Transit railroad tunnel from Fourteenth Street, East River, Manhattan, to Bedford Avenue, Brooklyn. The segments on the two contracts are identical in size and weight. On the first contract, approximately 10,000 tons have been delivered, leaving 30,000 tons to be produced on the two contracts. The following is a list of the tunnel segment contracts booked by the Davies & Thomas Co. since it began the manufacture of this kind of work in 1905:

Tons

Pennsylvania tunnel 57,340

East River tunnel 20,525

Hudson & Manhattan Railroad tunnel 13,312

Steinway tunnel 13,794

Harlem River tunnel 2,165

East River Gas tunnel 2,000

Roof tunnel over the New York Central railroad tracks 838

Sewer tunnel, Borough of Queens, Brooklyn, NY 11,000

Philadelphia Electric In-Take tunnel 2,000

Rapid Transit railroad tunnel 18,000

Rapid Transit railroad, 14th street tunnel 22,000

Total 162,971

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