section, at the stoppage of work, shall be discarded and not used under any circumstances. In no case shall concrete be deposited upon a frozen subbase nor shall a completed green floor be exposed to freezing weather without tarpaulin, canvass or some other such protection spread over it.

Forms.-All wood forms shall be thoroughly cleansed of old mortar and dirt and wetted. Metal forms should be coated with oil, soft soap or whitewash before depositing concrete against them. It is undoubtedly a mistake to use the individual slab practice, with expansion joints for a molding floor. The edges of slabs whether rounded or square will in time break down. Once concrete suffers a bad hole or crack it deteriorates at that point in a manner similar to a tooth with perforated enamel.

Expansion Joints. It is recommended that no expansion joints be provided in the finished floor, the concrete in forms being struck off level with sharp edges; the forms removed when the concrete has hardened to the point where there is no danger of a slump, and the sides so exposed well roughened in order that when the concrete in the adjacent slab is laid thereto it will thoroughly knit into the roughened surface provided. To assist in perfecting a knit it is well to brush the roughened surfaces with a mixture of neat cement grout of a creamy consistency just previous to placing the fresh concrete against the side surface of the preceding slab which has been so prepared. Grout should not be used after it is 45 minutes old. Special pains should be taken to eradicate any surface seams, crevices or edges as the floor is bound to be weak and subject to disintegration at such points.

Finishing. When finishing a concrete molding floor to be terminated at the gangway wherein wood block are to be installed, the edge of floor should be finished off with a light angle iron, the web of which should equal the thickness of the floor, pressed or embedded firmly into the concrete as a curbing. In a strictly slab floor, not reinforced, the limit is 100 square feet. In a continuous foundry floor where the forms are used rather as a convenience while placing the concrete and to provide for the immediate contraction during setting, the slabs may be increased into whole sections sized conveniently, it only being necessary to complete each section through continuous operations without any stoppage of work for any cause.

The finishing and curing of a concrete molding floor is of prime importance. After placing the concrete it should be struck off with a sweep or strike-board to the established grade of the forms. Further working should be avoided; the wood float or trowel being absolutely taboo. The surface must not under any circumstances be troweled or finished smooth. When the floor has set to a consistency of stiff putty and will show no slump, a long-handled hand roller,

having parallel or checkered corrugations three-eighths (") inch deep and of sufficient weight to make full indentations in the concrete surface should be passed over the floor and gangways. These indentations will hold sufficient sand to prevent popping of molten iron when spilled on the surface of a concrete floor so finished, even though the floor be swept. Furthermore, the indentations provide nests to collect and hold the shot iron which are apt to throw workmen.

Curing. Perhaps the greatest cause for the failure of concrete floors may be traced to the entire lack of or insufficient curing of newly laid green material. All forms of concrete show great increases in strength under favorable curing conditions as compared with specimens which have been allowed to air dry. In arid regions and during warm weather freshly laid concrete is exposed from the moment it is laid to rapid evaporation of the mixing water. Therefore the chemical action in process during "setting" is retarded and a portion only of the strength is secured. Concrete floors of any character should be covered with sand, shavings, saw-dust, or some such material as soon as the floor has set to a consistency which will permit the placing of such a topping, which in turn should be soaked twice daily. A 21 to 30-day storage is apparently about the ideal length for the best curing results, as by the expiration of these time limits the strength and wearing qualities will have increased some 150 to 200 per cent over the original strength of the same floor allowed to air dry. It is urged that every concrete floor be cured at least 10 days, the very minimum being three days.

The use to date of prepared wood-block for molding floor gangways, under the cupola spouts and on charging platforms has met with splendid success. The spillage of iron on wood blocks merely chars it slightly, molding sand filling in the char holes and preventing further burning.

Aside from the first cost of wood blocks, which must themselves be laid on a concrete foundation, this form of pavement for a molding floor seems quite ideal except perhaps in foundries running string sand floors, such as stove shops, where the molder's shovel comes in contact with the floor continually. It is thought the slight projections of the corners of the blocks may present a roughened surface to the shovel and annoy the molder.

In conclusion, the author wishes to acknowledge his indebtedness to Prof. Duff Abrahams, Lewis Institute, Chicago, and the Portland Cement association.

Discussion Molding Floors

MR. LAMBERT T. ERICSON.-It is generally conceded that the first and most important step to take in cleaning up and modernizing a foundry consists in building a smooth and durable floor and establishing a permanent level to work upon.

The selection of the materials to use on the floor is an important matter. Mr. Haley has carefully pointed out that it is necessary to take the most careful precautions in the proper selection and grading of the materials in the concrete, to add just enough and not too much water and to take plenty of time to let the concrete cure; that neglect in any of these details may result in failure; that the only material in the aggregate which is standard in all parts of the country is the portland cement and consequently, the work must be done under the supervision of an expert who thoroughly understands concrete My own experience is that very few concrete experts agree as to the best specifications for the mixture. A great many disagree with Mr. Haley on the point of the amount of water to use on account of the physical impossibility of properly placing such a dry mixture. Consequently specifications will not be followed to the letter, if the work is left to a local expert.

Mr. Haley recommends three to four weeks curing of the cement and urges a minimum of 10 days. This feature of delay makes it almost impossible for the operator to consider the construction of concrete floors in any except new or unused buildings.

A wearing surface of creosoted wood blocks over a concrete sub-base is almost indestructible under traffic. The blocks are equally adaptable to molding floors and in the truck ways and impact does not cause the wood block to disintegrate. They are not affected by temperature changes and are warm under feet in winter and cool in summer and under the heat of a foundry. Changes and repairs are easily and economically made. Wood block floors are popular with the workmen, im

prove their health, decrease the sickness and consequently the amount of absence from work and decrease the accidents around the plant. Properly constructed they are waterproof and dry and, as Mr. Haley has stated, they are impervious to spillage of iron, since they merely char slightly, molding sand filling the char holes and preventing further burning.

Creosoted wood blocks lend themselves with equal facility to the construction of new floors, the resurfacing of old concrete floors, or the resurfacing of concrete floor slabs, of reinforced concrete buildings. Under stress of necessity, wood blocks can be installed within 48 hours of the time of the construction of the concrete sub-base and the floor is available immediately thereafter.

Wood block floors recently have been installed in a large motor foundry in Flint, Mich., without holding up production in any way. The foundry is located on the second floor of a reinforced concrete building. The coreroom and core ovens are in one end and the foundry in the other end. The floor area is approximately 108,000 square feet. The original wearing surface of concrete was surfaced with a dry cement cushion, upon which wood blocks 21⁄2 inches thick were installed, the work being done in sections entirely at night, with company forces, under the supervision of the wood block manufacturers' service department.

The installation of the blocks is comparatively simple and the average foreman can take care of the work very easily, after having secured a little instruction. Wood block floor construction requires expert supervision principally for the instruction of the local foreman.

Wood blocks must be properly manufactured and the floors constructed under proper specifications. They require a solid, immovable base, preferably concrete. The blocks must be laid with tight joints, filled with coal tar which, to make them waterproof and to make them stand up under the wear and tear. The objection mentioned of the possible roughness causing the molder's shovel to come in contact with slight projections at the corners of the blocks, need not receive serious consideration. Proper construction methods will insure a smooth floor.

Audible Signals in Foundries

By VLADIMIR KARAPETOFF, Ithaca, N. Y.

The following types of audible signals are actually in use in various foundries: Electric horns similar to those used on automobiles, Fig. 1; air or steam whistles, sometimes electrically operated from a distance; and bells and gongs, either single stroke or continuous. In an efficient up-to-date foundry such audible signals should be used for at least the following five

purposes:

1-For calling any important employe to the nearest telephone no matter where he may be; this presupposes a prearranged code and some simple device for sounding calls.

2-As extensions to telephone bells in noisy places; a foreman may not hear his telephone bell when away from his desk, but he would most likely hear one or more loud horns or shrill whistles mounted in the shop.

3-For purely local needs and signals, for example, to indicate the beginning and the ending of pouring, to call a craneman or an electrician to some prearranged place, etc.

4-As warning signals of danger on cranes, hoists, locomotives and trucks, especially when a ladle with molten metal is in motion.

5-For sounding fire-alarms.

Imagine yourself sitting as an observer in the molding and pouring department of a large foundry properly equipped with audible signals. You will soon hear one or more electric horns sounding a code number, for example, one, one and two (1-1-2). This may mean that the superintendent is wanted in his office, but that there is no particular hurry about it. Had the call been one, two, two (1-2-2), it would have meant a hurry call and you probably would have seen the superintendent running to the nearest telephone.

Soon afterward you may hear two long blasts of an air whistle, signifying that everything is ready for pouring in the north aisle. A few minutes later it might be followed by a continuous ringing of a bell to warn the workers that a big ladle full of molten metal is being carried by the crane.