The shaft itself was piled, welded, and drawn on the porter-bar in the usual manner, until the location of a crank was reached. Then a part of the work some distance from the new end was squared, as shown in [Fig. 3017], and on this square the saddle was piled to heat and weld, as shown in [Fig. 3018]. As will be seen, the saddle rested upon the outer lines of the angle. The first blow was struck square on the top of the saddle, and after three or four blows the job presented the appearance shown in [Fig. 3019]. The piece was now turned so as to lie as shown in [Fig. 3020], and worked with blows on the sides to the shape shown in [Fig. 3021]. This opened the top of the juncture of the saddle and squared the shaft down to the point where the weld was good. The piece was then turned back to the position shown in [Fig. 3019], and worked with blows which again closed the angle on top, and made the weld good all through. The piece was then returned to the furnace, and at the next heat the saddle was squared up and finished, and the cap was piled on top of the saddle, as shown in [Fig. 3022]. The cap was welded on at the next heat, and two cheeks, like that shown in [Fig. 3023], were laid upon one flat of the crank and pinned with 15⁄8-inch round pins. One of these pins is shown in the figure. Bits of iron were put under these cheek pieces in the usual manner. As the cheeks were very much smaller in section than the crank body, it was necessary to turn them over away from the fire, or else the cheeks would be burned before the crank body was hot enough to weld. To prevent the cheeks from falling off in the furnace the pins were put in as described before heating. After two cheek pieces had been welded on one side, two more were added on the opposite side, and then the crank was finished, as shown in [Fig. 3024].
As will be seen by inspection of [Fig. 3012], the weld between the cap and the saddle comes about the middle of the wrist, and the cheek pieces support the cap sideways. By means of the piles and welds described, the grain of the iron was so disposed as to offer the most resistance to working strains. This method was devised by Mr. Farrell Dorrity, of the Morgan Iron Works.
Forging Large Crank Shafts.[45]—The following paper describes the method of forging marine crank shafts adopted at the Lancefield Forge, Glasgow. It will be better understood if a short account is first given of the ordinary methods in use for the same purpose.
[45] From a paper read at the Glasgow meeting of the Institution of Mechanical Engineers, by W. L. E. MacLean.
Fig. 3025.
Fig. 3026.