Electromagnet: bolt and nut, 5/16 by 2; 2 washers; also the spool of hook-up wire used in the electric pencil ex- periment. Electromagnet Cover: tin-can strip, 1-1/2 by 3-1/2. Vibrator Arm: tin-can strip, 1 by 10. Slider Clip for Vibrator Arm: tin-can strip, 3/16 by 1. Contactor: brass screw, 1 long. Contactor Holder: wood, 1 by 1 by 3/8. Code Key: tin-can strip, 1/2 by 3. Base: wood, 7 by 9 by 3/4. Battery: 6 volts (12 volts would be even better). Minor items: 6 or 8 small nails, 4 round head screws.
How to Build the Parts
WINDING THE ELECTROMAGNET: Place a washer at each end of the bolt and engage the nut so that it just covers the end of the bolt. Starting at either end of the bolt and leaving about 6 of wire for making connections, begin coiling the wire around the bolt between the washers. Carefully wind one layer along the length of the bolt and another layer back toward the starting point. Keep doing this until several layers of wire have been put on. Plan to finish the winding at the opposite end from which you started. Cut off all but 6of wire. Now wrap some tape around the coil to keep it from unwinding.
