Those who wish to secure a set of castings from their own patterns can possibly save part of the expense if they do not consider the extra labor of first making the patterns.
Two types of motors are described, one vertical and the other horizontal. Both are intended to operate on a battery current of 3-6 volts and if carefully built will deliver a surprising amount of power.
FIG. 60.—Details of the Field Frame of the Vertical Motor.
A VERTICAL POWER MOTOR
The Field Frame is shown in detail in Figure 60. The exact shape and dimensions are best understood by a careful examination of the drawing.
The pattern for the field may be made of the same shape and practically the same size as indicated for the finished casting because the "rapping" or jarring which the pattern will receive in the foundry in order to free it from the sand mould will enlarge the mould sufficiently in a casting of small size to make up for any shrinkage which takes place upon the cooling of the iron.
The only exception to this is in the tunnel where the armature rotates. This should measure one and three-quarter inches in diameter when finished and should be slightly smaller in the rough casting so that there is enough material to allow for truing and bringing to equal size.
The Armature may be of two types, three pole or six pole. The three-pole armature is the simpler, but the six-pole type is the smoother running and gives the steadier power. The details and dimensions are shown in Figures 61 and 62. One of the armatures should be selected and a pattern built.
