The dimensions and form of the field stampings are given in [Fig. 4]. A number of these cut from thin sheet iron to make a pile ⁵⁄₈ in. thick when clamped together is needed. The dimensions of the opening to carry the armature should be a little less than that indicated in the sketch, as it will be necessary to true it up after the stampings are fastened together. Use one of the stampings as a pattern, and drill seven small holes in each, as indicated by the letters O, P, Q, R, S, T, and U. Fasten them together with small rivets, and true up the opening for the armature to a diameter of 1¹⁄₈ in. Drill five ¹⁄₈-in. holes, as indicated by the letters V, W, X, Y, and Z, to be used in mounting the pieces, which are to form the armature bearings, brush supports, and base of the motor.
Fig. 5
Fig. 6
Detail of the Field-Structure Supports, One Being for the Left Side and the Other for the Right. The Supports are Shown in the Place at the Right
Cut two rectangular washers from a piece of thin fiber insulation, with outside dimensions of 1¹⁄₈ in. and 1¹⁄₄ in., and an inside opening, ¹⁄₂ in. by ⁵⁄₈ in. Cut open these washers and slip them in position on the portion of the field marked ZZ. Wrap two turns of the cloth insulation about this part, which is to form the field core, and wind the space full of No. 18 gauge enamel-insulated copper wire. Give the completed winding a coat of shellac. The terminals of this winding should be brought out through two holes drilled in one of the fiber washers, one near the core and the other near the outer edge. It is better to have the field terminals at the lower end of the part ZZ than at the upper end.
Fig. 7
Detail of the Brush Holders, One Inch Long, with Holes as Shown
Now cut two pieces from ¹⁄₁₆-in. sheet brass, similar to those shown in [Fig. 5]. Place them on opposite sides of the laminated field structure, shown in [Fig. 4], and carefully mark the position of the holes, V, W, X, Y, and Z, as indicated in Fig. 4, and drill ¹⁄₈-in. holes, where the marks were made. Lay out and drill ¹⁄₈-in. holes, A, B, C, and D, Fig. 5. Bend the upper portion of the pieces at right angles to the lower portion, along the dotted lines E, and then bend the end of the horizontal portions down along the dotted lines F, until they are parallel with the main vertical parts of the pieces. The latter should be bent so that one forms the left support and the other the right, as shown in [Fig. 6].
Bend the projections G and H at right angles to the vertical main parts. The parts at the bottom are bent, one back along the dotted line J and forward on the line K; the other forward on the line L and back on the line M. The pieces are then mounted, on the side of the field structure, as shown in [Fig. 6]. The supports are fastened in place with five small bolts. The grooves N and O, in [Fig. 5], are used in mounting the motor on the axles of the truck. They will not be cut until after the truck is constructed.