[Illustration: FIG. 58.—Details of the two different Pieces of Sheet Iron used in building up the Core. Sufficient of each piece are required to form a pile of each three-quarters of an inch thick.]
A step-down transformer cannot be used to recharge storage cells or for electro-plating unless the current is first passed through a rectifier.
A transformer is both in principle and construction really very simple.
It consists simply of two coils of wire wound around an iron core. One coil consists of many turns of fine wire and is connected to the 110 volt alternating current. This coil is called the *primary*. The other coil consists of a smaller number of turns of larger wire and is called the *secondary*. The lower voltage currents are obtained from the secondary.
The first step to take in making a transformer is to procure some sheet iron of the sort used for making stove pipes. It is called stove pipe iron.
This iron will have to be cut into a number of pieces like A and B in
Figure 58.
The exact shape and dimensions are most easily understood from the illustration. A somewhat resembles a three-pronged fork, while B is simply a strip 2 5/8 inches long and 1/2 inch wide.
[Illustration: FIG. 59.—The Method used in piling up the Strips to
Assemble the Core.]
A sufficient quantity of each piece will be required to make a pile three-quarters of an inch thick when tightly compressed.
The best method of procedure is to lay out one piece like "A" very accurately and then cut it out. Hammer it out perfectly flat and use it as a pattern to lay out the other pieces with. The cutting can be done with a pair of ordinary tin snips. The pieces should all be cut very accurately and truly so that they will match when piled up. The rough edges of the iron can be smoothed up with a file.