FIG. 37.—The Brass Contact.
The contact and the brush will have to be most carefully adjusted before the motor will run. The tip of the contact should make contact with the brush just before the armature starts to swing over the electromagnets and break the circuit just as the armature is actually over. The exact position will have to be found by a little experimenting. It is very necessary that the brush should be so adjusted that it only touches the ends of the contact as it swings around.
FIG. 38.—The Brush which bears against the Contact.
FIG. 39.—The completed Magnetic Attraction Motor.
The operation of the motor is very simple. When a battery is connected to the binding posts the circuit is not complete so that the coils are magnetized and can attract the armature until the contact touches the brush. When the contact and the brush touch, however, the circuit is completed and the armature will be drawn toward the electromagnets. As soon as it reaches a position over the ends of the cores, the circuit should be broken so that the momentum will carry the armature past and around into such position that the opposite end of the contact touches the brush and the operation is repeated.
A magnetic attraction motor of this type will usually have to be started by giving the shaft a twist with the fingers.