The brush holders are made of two pieces of hexagonal brass, each 1 in. in length, having a ¹⁄₈-in. hole drilled in the end to a depth of ⁷⁄₈ in., and a threaded hole in the other end, for a small machine screw, as shown in [Fig. 7]. Two holes are drilled and threaded in one side of each of these pieces. These holders are to be mounted, by means of screws, through the holes A, B, C, and D, [Fig. 5]. Each holder must be insulated from its support. The distance of the holder from its support should be such that the opening in its end is in the center of the commutator. The brushes are made of very fine copper gauze, rolled to form a rod. They are made long enough to extend about ¹⁄₂ in. into the holder, when they are resting on the commutator. A small spiral spring is placed in the holder, back of the end of the brush, and which will serve to keep the latter in contact with the commutator.
Temporary connections are made and the motor is tested with a six-volt battery. The construction of the motor may be modified as to the length of shaft, and other minor details, and may be used for other purposes by fitting it with pulleys, a countershaft, or other transmission devices.
Making String Solder
String solder of a size convenient for electrical work, or other soldering, where only a small quantity is desired, may be made by adapting a ladle for the purpose. Drill a small hole through the ladle near its upper edge. Melt the solder and pour it through the small hole, permitting it to fall on a slab of marble, slate, or stone. The ladle must be moved in zigzag lines in order to prevent the string from crossing and to make it possible to roll up the solder into rings of a convenient size.—Contributed by L. E. Fetter, Portsmouth, N. H.
To Prevent Wire Coat Hook from Turning
A good way to keep a common wire coat hook in an upright position is to drive a small wire staple over the smaller hook. In public places, such as halls, this will often prevent their removal and save considerable annoyance.—Contributed by Harry L. Dixson, Chicago, Ill.
¶The second coat of varnish should never be put on until the first has been “mossed” (rubbed) off; as, otherwise, it will not stick well.
Cement Grotto for an Aquarium
To build a small cement grotto for an aquarium, make a clay mold by roughly excavating two right-angled gutters in a lump of clay. Grease, or shellac, the mold after it is dry. Apply cement of about the consistency of putty, or dough, filling the gutters roughly so as to give a rocklike finish. Small shells can be stuck into the cement while it is yet moist. Before entirely shaping the cement, a piece of heavy wire is bent to conform to the shape of the grotto and set in for a reinforcement.