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424 THE MARINE REVIEW FIG. 1--WELDS ON THE RUDDER HEAD OF THE STEAMER LEOPOLDINA AFTER THE RISERS AND POURING GATES WERE REMOVED io ie ierm 'of .a pot. casting is mounted on the platen and _ turned on the outside to ithe desired diam- eter. The top edge is then faced Of - with one of the turret tools. Afterward the side cutting 'tool is used to cut four grooves, the top groove being the depth of the finished ring, but not being deep enough to cut through the casting because of extra material left on the inside. The final operation is finishing the interior and outside by means of a gang tool in the turret head which automatical- ly separates the top ring from the blank. For the next operation, the side cutting tool is lowered so that tae three upper teeth engage in the remaining three grooves, the lower feotn starting the cut. of a fourth groove, and the upper tooth finishing the cut of the top groove: This oper- ation is repeated until the casting is used up. The rings are then diagon- ally cut on a milling machine equipped with a metal slitting saw. To Revise Ship Rules Plans are under way for revising the classification rules of the Amer- ican Bureau of Shipping on the sub- jects of propellers and of internal combustion engines. The bureau called a conference in New York on June 7 with all the principal builders of internal combustion engines for the purpose of making a preliminary survey into the progress that has been made in the development of the diesel_engine. The decision to revise the rules of the official classification society of the United States in this regard was decided upon in view of the great progress made along these lines since the war. The American bureau also has its surveyors working on the propeller problem and in the near future will. probably issue new regulations on these. This action was prompted be- cause of the large number of acci-. dents happening to the propellers lt is felt that for the better protec: tion of shipping it is now necessary to devise stricter rules for the in- spection of propellers. Whee of Ady Necded for Preheaters Recent tests to determine the proper amount of air required for special thermit welding: gasoline and compressed air preheaters showed that 25 pounds per square inch seems to be a prac- tical minimum for operating preheaters. At this pressure, a single burner pre- heater will require approximately 25 'cubic feet of free air per minute and a double burner preheater approximately 50 cubic feet of free air per minute. For very large welds, where the walls of the molds are thick and the pre- heater gates longer than usual, a pres- sure of 40 pounds per square inch would be advisable. This would require ap- proximately 35 cubic feet of free air per minute for a single burner pre- heater. and 70 cubic feet of free air per minute for a double burner preheater. In the case of a large plant with a central air compressor plant, upon which demands are being made by many de- partments, the pressures quoted should be maintained at the outlet to which July, 1929 Welding a Rudder Head Application of thermit welding in con. nection with realignment and other gen- eral utility work on large marine Cast- ings is shown by the accompanying illys- trations of an unusual repair job re- cently made at the Brooklyn navy yard, New York. Figs. 1 and 2 show_-an interesting double weld made on the cast stee| rudder head of the steamship Leoporp.- INA, formerly the BLucuer, belonging to the Compagnie Generale Transatlan- tique. The purpose of this job was to make feasible some repairs needed on the rudder stock, the upper part of which fits into a key of the rudder head. In order to make these repairs, it was first necessary to remove the rudder stock from the rudder head. These two sections, however, had become s0 tight- ly locked together that it was finally decided to separate them by cutting through one side of the rudder head with an oxyacetylene torch. The rud- der head was then removed. In repairing the rudder head, it was necessary to cut through the side op- posite the first cut in order to make two welds instead of one and _ thus later equalize the effect of contraction when the welds had cooled. Having done this, the two parts were lined up so as to leave small gaps at the oxy- acetylene cut. As the next step a yellow wax pattern was applied to the space formed by the gap and shaped around the ad- jacent portions of the casting in the form ot a collar. A mold was then built around the wax pattern and the wax burned out of the mold by means of gasoline torches. This also served to preheat the parts of the casting near the welds, thus providing a more uniform contraction when the welds cooled. Both welds were poured simu!taneously, usiz 350 pounds of thermit, and the cross- head quickly returned to service. It is interesting to note that as this repair was urgent only 9 to 10 hours of work- the preheaters are attached. Tests were ing time were required to complete by the Metal & Thermit Corp., New York. the welding operations. 4 u ee 5-0)" =e 25 --> 4 CUT WITT? OXY-ACETYLENE TORC/T Ee ae ba ee ee fa ee ee <--2+0" CUT M771 OXV- ACETYLENE TORC/1 SS ---- FIG. 2--GENERAL DIMENSIONS OF LARGE CASTING WELDED WITH THERMIT