METHOD OF CONSTRUCTION OF CONCRETE SHIPS. ll 



arm, thus eliminating one man as well as considerably increasing the speed of bend- 

 ing. This device is capable of bending two ^-inch stirrups at a time. 



The heavy frame bars, ranging from i to i^/^-inch diameter round, were bent 

 by normal methods either on a hand-bending table or by a power-bending machine 

 such as the McKenna. Curved bends were difficult to make cold, because the bars 

 had a certain amount of spring and the templet or dogs around which the bending 

 was done had to be set to allow for the recovery in the bar. The quality of bars 

 was not imiform in this respect, which required testing each bar with the curved 

 templet after bending. Only a fraction of an inch tolerance could be allowed for 

 error in bending. At Jacksonville, Fla., all large bars with curved bends were bent 

 hot upon a cast-iron bending table about a steel templet previously set, and where 

 angle bends occurred in the same bars they were heated and all bends completed 

 at the same time. Bars for hot bending were heated to a dull red in a forge built as 

 a plate metal box about 3 feet wide, 3 feet high, and 60 feet long, filled with sand 

 to about 12 inches of the top, at which level a perforated pipe with removable %- 

 inch pipe plugs was extended the entire length of the forge and supplied with com- 

 pressed air at one end. A fire of coal and coke was built of any necessary length 

 along the forge, and accelerated by removing the pipe plugs through the range of 

 distance required to be bent and at as many places along the 60-foot bar as bends 

 were required. 



Hot bending proved very satisfactory as to accuracy, cost and speed, but con- 

 siderable saving would have been made had two forges been provided for the one 

 bending table. It was found impracticable to withdraw one heated bar from the 

 fire and replace it with a cold bar to keep the heating process continuous without 

 breaking up the fire and disturbing the heating of the other bars. The bending 

 crew were not occupied in bending more than about one-third of the total time and 

 could easily have bent the output of two forges whenever several bars were to be 

 bent to one radius and resetting of the templets on the bending table was not neces- 

 sary. That this process did not affect the strength of the bars is shown by the 

 tests made at the Bureau of Standards (Table 3, Plate 2). 



The vertical shell steel usually ^ or % inch diameter round, which has to con- 

 form where it is set into the bilge to the curvature of the ship, was bent on a hand- 

 bending table if the curve was of large radius, or in power machine if of small 

 radius or angle bends. 



Where this relatively light steel of long lengths was bent at a distance from 

 the point of construction, difficulty was experienced in some of the yards in trans- 

 porting it to the forms and maintaining the original bend. At one yard the bend- 

 ing table was placed within the hull forms, and the vertical shell steel was car- 

 ried directly from the bending table and set into position in the forms. If the other 

 work to be done in the hull has been carefully planned, so that the steel bending and 

 erection gangs will not interfere with other labor units, this method is quite satis- 

 factory. It is preferable to have all possible work done outside the hull forms, for 

 only a limited number of men can work efficiently within the hull. 



