Fig. 2981.
The seams between the spokes at the circumference of the hub are welded with bars as shown in [Fig. 2981], in which r r are two bars of iron which are operated by hand as rams. The wedge shape of the washers on their inside faces performs important duty in spreading the metal as well as simply compressing it, giving a much more sound weld than a flat washer or plain dish would.
The rim of the wheel is welded up as follows:
Fig. 2982.
In [Fig. 2982] are shown four spokes of the rim as they appear after the hub is welded. Into the V spaces, as a, b, c, d; wedges of metal, of the form shown at e, are welded, after which the surplus metal of e is cut away, and the rim is solid as at f. In this process, however, it is necessary to weld all the pieces on one side of the wheel, as at a b, &c., except one, which must be left unwelded until all the pieces save one on the other side are welded, and the wheel must be allowed to become quite cool before these last two pieces are welded. Otherwise the strain induced by the contraction of the wheel rim while cooling will often cause the rim to break with a report as loud as that of a rifle. In those cases in which this breakage does not occur the wheel will be very apt to break at some part of the rim, when subjected to heavy shocks or jars.
The [Figs. 2983] to [2999] (which are taken from Mechanics), illustrate the method employed to forge the rudder frame of the steamship Pilgrim.