The next work which will be necessary in the drawing room is a layout of the connections between fields and between the bus rings and terminal blocks at the side of the machine. Before the actual layout of these connections can be completed, however, it is necessary to determine exactly how the connections will be made as shown in Plate P.
Fig. 3 shows these connections laid out diagrammatically. An elevation of the machine is drawn rather roughly, showing the bus rings, the fields, the connections between fields, and the terminal blocks with connections to fields and bus rings. Note that the terminal blocks are shown separate from the machine and are revolved through 90 degrees in order to bring them to the same plane as the elevation of the machine itself. This is merely a matter of convenience, so that the connections can all be shown on one view.
Next, a development of the fields is shown at the left, looking from the inside of the machine. This is to indicate the relative location of the series and commu-tating field connections.
A small section showing the relative location of the bus rings on each side of the brush holder yoke is also shown so as to indicate the position of these bus rings with respect to the connections. It will be seen that this view and the others just discussed are merely diagrams which are provided in order that the draftsman may have something to start with in laying out the connections.
In Fig. 1, the draftsman has again shown an elevation of the machine and an elevation of each of the terminal blocks on the side of the magnet frame. The detailed drawings of the fields, Plate J, and of the bus rings Plate L, and the amount of current to be carried determine the size and number of bars or cables which should be used for the various connections. The assembly shows the exact shape of these connections and the manner in which the details must be worked out in order that there may be no interference between the various parts. Note how the cable connections between the bus rings and the terminal blocks have been indicated only by a line with arrowheads; that is, these cables will hang in a loop, and there is no use wasting time or effort in drawing them in completely.
Having completed the assembly layout of the connections, the details can be worked up as shown on Plate Q. This plate shows each bar of the connections laid out to exact shape and dimensions, and represents a very large amount of tedious work. The draftsman must check with extreme care every dimension given in the previous drawings which will affect the dimensions of these bars, and must be sure in every case that the bars will fit into the proper slots or terminals provided for them on other parts of the machine and will clear all of the fields, the framework, machine, or any other part where electrical or mechanical clearance is necessary. In each case, it is also necessary to determine as nearly as possible the developed length of the bars so that the copper can be cut before bending. The draftsman must also consider the assembler and see that the bars are arranged so that they can be assembled easily and so that the holding bolts can be slipped into place and drawn up without interference. While all of this means an exceptionally large amount of work on the part of the draftsman, it should be perfectly clear to the student just what method has been followed and what work is necessary in developing this"drawing.