Fig. 3009.
Fig. 3010.
Between both the slabs and the blooms there are placed rectangular pieces to hold them apart, and let the furnace heat pass between them, the arrangement of these pieces being shown in [Figs. 3009] and [3010].
[Figs. 3011] to [3024] (which are taken from Mechanics), represent the method employed to forge the crank shaft of the United States steamship Alert.
| VOL. II. | FORGING UNDER THE HAMMER. | PLATE XVII. |
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| Fig. 3011. | Fig. 3012. | |
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| Fig. 3013. | Fig. 3014. | Fig. 3015. |
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| Fig. 3016. | Fig. 3017. | Fig. 3018. |
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| Fig. 3020. | Fig. 3019. | Fig. 3021. |
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| Fig. 3022. | Fig. 3023. | Fig. 3024. |
[Fig. 3011] represents the crank shaft, and [Fig. 3012] an end sectional view, showing how the throws were built up. The first operation was to forge the saddles shown in [Fig. 3013], these being the pieces that are shown between the cap and the wrist.
These saddles were made in halves, each half appearing as in [Fig. 3014]. From a pile and weld of blooms on the porter-bar, enough to make the two halves, one half was cut off. The other half was then drawn down on the porter-bar, and the first half was then piled on the latter, as shown in [Fig. 3015]. The square cross bar goes clear across and projects about an inch at each side. The back pieces were short bits. The square cross bar makes the saddle less liable to split in welding it on to the square shaft. Two “caps” were also made before the forging of the shaft itself began. These are shown in [Fig. 3016], and their position in the finished work is shown in [Fig. 3012].