Internet Version [Naruhodo no Mori] Vol.54

by Yumiko Mori

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Vol.54   November 15th, 2000

Steel wire phone and steel wire voice speaker

Comparison with string phone

Home science experiments for mothers of elementary school children

Mom: "You are right. This is quite different from string phone."
Toshi: "Voice sounds completely different."
Mom: "I never expected this. This is a surprising discovery."

Materials

Steel Wire Phone

Steel wire	5 meter long
String
Plastic cups	several
An eyeleteer, a pair of pliers, and a Scotch tape

Steel wire voice speaker

2 plastic bottles	1.5 liter size
Steel wire	3 meter long
A rod (for example, a core rod used in Fax paper)	(approximately 1-2 cm in diameter)
Color markers, a cutter, a pair of scissors, and a Scotch tape

How to make steel wire phone

     Required time: 5 minutes

1. Using an eyeleteer, make a small hole on the bottom of each cup.

2. Pass a steel wire through the cup holes and twist the end of the wire, so that the wire doesn't come off from the cups.

3. Two people hold the cups at both ends and start talking through the steel wire phone. They should give hand signs if they can hear each other speaking.

   
   * Don't bend or hold down the wire.

   * String phone works only if the string is pulled and thus under tension.
   But you can hear through steel wire phone, even if the wire is not under tension. Why?

   * You may want to try changing the thickness of the wire, or may want to use fishing strings or kite strings.

   
   

How to make steel wire voice speaker

     Required time: 50 minutes

1. Have 2 plastic bottles ready. For each bottle, put a plastic cup on the top of the bottle with the cup being upside down. Mark the cup edge with a marker.
   Add an incision along the marked line and then cut off with a pair of scissors.
   Make sure not to cut off beyond the marked line.

2. Also cut off the bottom from each bottle.

3. Wrap a piece of steel wire around a rod. The piece of steel wire becomes like a spring.

   

4. Assemble the bottles, the cups, and the steel wire, as shown in the illustration.
   Put the bottles and the cups together with Scotch tape. Also tape between the two bottles.

   

   
   * If the spring part is too long, you can pull out it through the plastic cup after you assemble all the parts.
   It works best if the spring doesn't touch the bottle.

   * A commercially sold spring may produce better sound.

Why steel wire phone has disapeared?

A science experiment book written by Jun Ishihara in 1928 mentions about steel wire phone made from steel wire and used cans. Some years later, string phone has become more popular. New one has survived, but the old one has disapeared. Both phones were interesting to try, and it was fun to compare those. But why is only string phone widely known?