103. Trembling Armature. Fig. 50. Armatures to be used upon electric bells, automatic current interrupters, buzzers, etc., may be called trembling armatures. They may be made entirely of sheet-tin. The part, F, which gives it the spring, should be about ⅝ in. wide. Its length will depend upon the particular apparatus to be made. It is made of 2 thicknesses of thin tin. See Fig. 50 for dimensions. The part N projects beyond L. This may be used to tap against a regulating screw, or to fasten a hammer on for an electric bell. The part, L, should have about 4 layers of tin on each side of F, and it should pinch F tightly.
Fig. 50.
104. Trembling Armature. Fig. 51. When very rapid motions are desired in a trembling armature, [App. 77] will be a little heavy. A light and quick-acting armature can be made of sheet-tin. The exact dimensions will depend upon the use to be made of it, but you will find the following a guide. Cut the part, B, E, out of thin tin. The covers and bottoms of tin cans are thinner than their bodies. The narrow part, B, should be about ¼ in. wide and 2 in. long for a small apparatus, while E may be ¾ in. square. Through E is a screw, which holds it firmly to a wooden piece, D, about ¾ in. square. The part, E, can be made longer than its width, so that two screws can be used; this will keep A from jarring up or down.
Fig. 51.