The brushes, supported on their fibre blocks, should be mounted on the bearing by means of two screws passing through the holes in the bearing into the block. The position of the brushes should be such that the shaft passes between the two upper ends but does not touch them unless the small "contact" crank mentioned above is in proper position to do so. The proper adjustment of the brushes so that they will make contact with the shaft at the proper moment will largely determine the speed and power which the finished engine will develop.
FIG. 58.—Showing how a Flywheel may be made out of sheet iron.
Two binding posts should be mounted on the right hand end of the base so that the engine can be easily connected to a battery. Connect one terminal of the right hand electromagnet to one of the binding posts. Run the other terminal of the electromagnet to the brush on the opposite side of the shaft. Connect one terminal of the left hand electromagnet to the other binding post and run the other terminal to the brush on the opposite side of the shaft. Save for a few minor adjustments, the engine is now ready to run. Connect two or three cells of dry battery to the two binding posts and turn the flywheel so that it moves from right to left across the top. Just as the crank passes "dead center" and the armature starts to move back away from the left hand magnet, the small contact crank on the shaft should touch the left hand brush and send the current through the right hand magnet. This will draw the armature over to the right. Just before the armature gets all the way over to the right, the contact should break connection with the left hand brush and interrupt the current so that the inertia of the flywheel will cause it to keep moving and the armature to start to move over toward the left hand magnet at which point the contact on the shaft should commence to bear against the right hand brush, thus throwing the left hand magnet into circuit and drawing the armature over to that side. If the brushes and the cranks are in proper relation to each other the engine will continue to repeat this operation and gradually gain speed until it is running at a good rate.
The appearance of the engine can be improved by painting the metal parts black and the flywheel red. The magnets can be wrapped with a piece of bright red cloth to protect the wire against injury and also lend attraction to its appearance in this way.
CHAPTER IV SMALL POWER MOTORS
In order for a motor to develop any appreciable amount of power it must be much larger than any of those which have been described in these pages so far, and must be constructed in a most painstaking manner. It will be necessary to use a great deal more iron in the field and armature and also to make the space between them as small as possible. A motor having a small separation between the field poles and the armature will develop more power than one having a greater separation.
FIG. 59.—A Vertical Battery Power Motor.
The most efficient types of small power motors have laminated field and armature frames, that is, they are built up of a large number of thin metal punchings. The amateur experimenter who has limited facilities for carrying out his work would find it difficult to make parts of this sort to good advantage and so the motors described here have been designed with cast iron armatures and field frames.