This is a classic design from the 1938 book "Things a Boy Can Do with Electricity" by Alfred Morgan.
You can make this simple model electric motor with the following materials:
Block of wood, 6 x 4 x 3/4 inches (app. 152 x 101 x 19 mm)
Three 20-penny nails
Glass tubing (short piece)
Magnet wire, No. 20 to No. 24
"Using a hacksaw, cut the heads off two twenty penny nails 2 3/4 inches (70mm) from the point. Drill two small holes in the base on centers 4 3/8 inches (111mm) apart. Drive the cut nails into these holes until they stand 2 1/4 inches (57mm) high above the base. These nails form the cores of the field magnets. The field magnets supply the magnetic field in which the armature revolves.
The motor armature is 20-penny nail pushed into a hole in a large cork. The cork is provided with a bearing made of glass tubing which has been closed at one end by holding in a flame. The piece of tubing should be about 1 3/4 inches (44 mm) long and 1/4 inch (6mm) in diameter.
A nail, driven through from the underside of the base exactly halfway between the two field cores is the pivot upon which the armature turns. Adjust the glass tubing in the cork until the ends of the armature (nail) are level with the upper ends of the field core (nails).
Each field core is wound with four layers of No. 20 to No. 24 magnet wire. Both coils are wound in the same direction.
The armature is also wound with four layers of wire (of the same size as that used for the field). The armature winding is divided into two sections, one on each side of the cork. Both sections are wound in the same direction. The nail should be wrapped with two or three layers of thin paper before the wire is wound in place.
The terminals of the armature winding are scraped bare of insulation and fastened to the glass tube so as to form what is known as the commutator. It is by means of the commutator that electrical connection is established with the revolving armature coils. The wires are fastened to the tubing with thread or narrow strips of adhesive tape.
The outside terminals of the field windings should each be connected to a binding post. The inside terminals are scraped bare of insulation and used as brushes. The brushes are fastened in position by wrapping each one around a small nail or brad driven into the wooden base."
Connect several dry cells to the binding posts. Make certain everything is wound and connected correctly, and that the brushes are in the right position. Give the armature a twirl with your fingers, and the motor should turn.