Part 10

The rotating electromagnet will have to be connected to the 2 wires through which we pass the current. Since it's rotating on a center shaft, we can't have a solid connection. Instead we have to extend the wires from the coil out along the shaft and let the electric contact be made with brushes which touch the wires along the shaft.

This is a simple way to reverse the current in the coil of the electromagnet.

Increasing Efficiency

Instead of using only one pole of a stationary magnet, we can use both. This is done by shaping the stationary magnet around the path of the rotating electromagnet. This way we have the benefit of the attracting and repelling forces from both poles. The effect is doubled.

We can also wrap wires around this circular iron and make an electromagnet of it. But when we wire this magnet we use no brushes because we want the current to flow in one direction only.

The stationary electromagnet is called the field. The rotating electromagnet is the armature.

WHAT TO DO: Make A Motor

Tools Needed:

Pocket knife, hammer, vise (or 2 pairs of pliers).

Materials Needed:

1 roll of No. 24 enameled wire 1 roll of electrician's tape 3 - 4" (20-penny) nails 4 - 2-1/2" (8-penny) nails 4 - 3" brads (10 penny) Wood board for motor base 2 staples or 4 small brads 2 tacks 2 - 3 volt dry cell batteries (or a 6 volt transformer).

Step No. 1-Armature

Wrap about 1-1/2" of a 4" nail with two layers of tape. This will be the shaft.

The iron core will be made of two pairs of 2-1/2" nails. Wrap tape around each pair with heads and points alternated.

Center both pairs on each side of the shaft. Place them about 1" from the head of the shaft nail. Wrap them together with two layers of tape from tip to tip.

Start at the shaft and wind No. 24 enameled wire to one end and back. Then do the same on the other end. Always wind in the same direction. Leave 6" of spare wire at start and finish.

Step No. 2-Commutator

Scrape all insulation off the ends of the wire. Bend the bare ends back and forth as shown. Lay them flat over the taped shaft-one on each side of the shaft.

Hold the commutator down with narrow strips of tape. Wrap tightly near the core and at the opposite end.

Step No. 3-Field

Make the core by bending two 4" nails in the middle at right angles. Space the heads about 3" apart to form a horseshoe. Wrap together with two layers of tape.

Wind about 400 turns of wire around the center. Leave 4" of spare wire at start and finish. Attach to wood base with staples at each end of the wire. Small brads, bent over, will do just as well.

Step No. 4--Armature Supports and Brushes

Scrape the insulation from the ends of two 6" pieces of wire. Tack them to the base and bend them as shown to make brushes.

Drive two pairs of 3" brads into the base about 3-1/4" apart and in a line midway between the field poles. Wrap wire around the supports to form armature bearings.

Scrape insulation off ends of wire from the field. Connect one end to a brush wire.

Assemble As Shown

Adjust the position of commutator and tension of brushes against it for best operation.