Chapter VI: Section 2: , the inside terminal of coil F and the outside terminal of

coil D should be connected to Section 3.

The wires leading from the coils to the commutator should be just as short as it is possible to make them and after being soldered should be bound down tightly with linen thread or string.

The bearings are both cast from brass. The details are shown in Figure 66 It will be necessary to make up wooden patterns and send them to a foundry. The location of the holes can be ascertained from the illustration.

Each of the brushes consists of a piece of strip copper, one-quarter of an inch wide and one and three-eighths inches long mounted in a brush holder made of one-quarter inch brass rod. The brush holder is one inch long and is turned down to a diameter of one-eighth of an inch at one end for a distance of nine-sixteenths of an inch and then threaded with a 6-32 die. The opposite end is slotted to receive the brush. The threaded portion of the holder is slipped through the holes, "B and B", in the bearing and prevented from making contact with the latter by a fibre bushing.

A fibre washer should also be slipped over the holder on each side of the bearing. Two hexagonal nuts are placed on the threaded stem. One serves to clamp the holder in position and the other to hold the wire used to make connection with the brush. The right hand brush should bear against the under side of the commutator and the left hand brush against the upper side.

After the armature has been assembled in the bearings and mounted on the field frame it should revolve freely without friction and without any possibility of its striking against the field poles.

The binding posts are mounted in the holes, "PP" in the lower parts of the field frame. They are insulated by two fibre or paper busings. The left hand binding post is connected to the inside terminal of the field winding. The outside terminal of the field winding is connected to the left hand binding post. The right hand binding post is connected to the right hand brush.

The base of the motor is a wooden block of suitable size.

The motor is of the series type because all the current flows through both the field and armature. A current of 2 to 6 volts will operate the motor. The pulley or gear required in order that the motor may be used as a source of power will depend upon the work for which the motor is to be employed. A small grooved pulley such as as that shown in Figure 63 may be fastened to the shaft with a set screw and will prove most useful for general purposes.

A HORIZONTAL POWER MOTOR.

The horizontal motor does not differ very materially from the vertical one just described.

The field frame is, however, made in two pieces, and the bearings are cast directly on the frame. The details and dimensions are given in Figures 68, 69 and 70.

The field winding consists of six layers of No. 18 B. & S. Gauge double cotton-covered wire wound on a spool or bobbin.

The core of the bobbin consists of a piece of five-eighths round steel or iron rod, two and seven-sixteenths inches long. Two circular fibre heads, one-eighth of an inch thick and one and one-half inches in diameter are mounted on the core one-half an inch from one end and fifteen-sixteenths of an inch apart. The ends of the core are set in the holes, "C, C," in the two parts of the field frame and held in position by two set screws threading into the holes "S" and "S."

Either the three-pole or the six-pole armature may be used. The commutator and brushes are identical with those used in the vertical type of motor.

The shaft is three-sixteenths of an inch in diameter and four inches long. The brushes are mounted upon a brush arm which is shown in detail in Figure 63. This is made of three-sixteenths inch sheet brass. The brushes must be insulated from the arm by fibre washers and bushings in the same manner as they were from the bearings on the vertical motor.

The holes in the bearings on the field frame are drilled out three-eighths of an inch in diameter and then brushed with a piece of three-eighths inch brass rod five-sixteenths of an inch in diameter having a three-sixteenths inch hole through the center.

Any of the Following

Practical Books

*will be sent At Once, Post-paid on receipt of price.*

_There is very little danger of losing currency in a letter if the
following directions are observed:_

Cut a circular hole the diameter of

the coin in a piece of cardboard, of

sufficient size to fit closely in the

envelope. The cardboard should

be no thicker than the coin.

Insert the coin in the hole and paste

a piece of paper on both sides of

the cardboard to prevent the coin

from falling out.

COLE & MORGAN

Publishers of the Arts and Sciences Series

P.O. Box 473, City Hall Station New York, N. Y.

*Experimental Wireless Construction*

*EIGHTY-SIX PAGES NINETY-THREE ILLUSTRATIONS*

*Only 30 Cents, Postpaid*

Here at last is the book which every young experimenter interested in constructing his own wireless apparatus has been looking for.

A book which tells how to build apparatus which anyone would be proud to own. It is a more advanced book than "Wireless Construction and Installation for Beginners," and describes apparatus which is much more elaborate and sensitive. The instruments have all been the subject of considerable experimental work and study. All the apparatus has been put to practical test and carefully improved by clever experts. By purchasing this book you get the benefit of vast knowledge and experience and are enabled to build far better instruments than by following your own designs and haphazard methods.

*Partial Contents*