The drawing herewith shows a simple electric motor which can be easily constructed by any boy who is at all handy with tools. I made this motor many times when a boy and can say that if carefully constructed it will run with greater rapidity than the more expensive ones.
Illustration: Electro-Magnet Motor
A common magnet which can be purchased at any toy store is used. The one shown is 3-1/2 in. in length. The armature core is a strip of 1/16 by 1/4-in. iron, 2-1/4 in. long, bent U-shaped and fastened to the wood flywheel. Each leg of the armature is wound with 10 ft. of No. 24 gauge magnet wire. The commutator is made from an old 22 cartridge filed into two equal parts, each being a half circle, both of which are made fast to a collar on the shaft E. Each half of the commutator must be insulated from the other half. The collar can be made by wrapping paper around the shaft until the required size is obtained.
The top end of the shaft runs in a hole bored in a brass support, B, which is screwed on the end of a piece of wood mortised in the base, as shown in Fig. 1. The lower end of the shaft runs in a glass bead, D, which is fastened to a small piece of brass with sealing wax. The small brass piece is fastened to the base with screws. The bead should not have an eye larger in diameter than the shaft. The shaft is made from an old discarded knitting needle. The brushes are fastened to each side of the upright piece of wood supporting the brass bearing B.
The connections to the battery are shown in Fig. 2. Each half of the commutator C is connected to the coils AA as shown in Fig. 1. --Contributed by J.M. Shannon, Pasadena, Calif.