# How a Gramophone Works

By C

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/jHOdjUHMxgiV)

## Guide

### 1. A music machine with no plug

This is a wind\-up gramophone, the kind families played about a hundred years ago\. It has no electricity at all: just a spring, a needle and a big horn\. Let's find out how it turns a groove into music\.

Drag empty space to turn the gramophone and look all around it\.

### 2. Wind up the spring

Turning the crank coils a strong steel spring inside the cabinet, called the mainspring\. Like winding a toy car, this stores energy for later\. A ratchet stops the spring from simply springing back\.

You can also tap the crank handle on the side of the cabinet\.

### 3. A steady seventy\-eight

As the spring slowly unwinds, a chain of gears turns the turntable about 78 times a minute\. A governor keeps that speed steady: three spinning weights swing outward and rub a brake pad when it runs too fast\.

Too slow, and the music would sound low and dragging\.

### 4. One long spiral groove

A record is not a set of rings\. It holds one single groove that spirals from the outer edge toward the centre\. One side of a ten\-inch record plays for about three minutes\.

Records like this were pressed in shellac, a hard and brittle material, not vinyl\.

### 5. The needle wiggles

This model magnifies a tiny piece of the groove\. Its walls wiggle from side to side in the shape of the recorded sound\. As the record turns, the steel needle rides the groove and is pushed left and right hundreds of times a second\.

The real wiggles are thinner than a hair\. The model makes them much bigger so you can see them\.

### 6. The soundbox shakes the air

The needle is fixed to a small lever in the round soundbox\. The lever pushes a thin disc called the diaphragm in and out\. As it trembles, the diaphragm pushes and pulls the air, making tiny sound waves\.

Early diaphragms were made of mica, a thin, glassy mineral\.

### 7. The horn makes it louder

On their own, those waves are small and quiet\. The horn starts narrow and flares wide, helping the little diaphragm push on much more air\. It adds no power of its own; it lets the sound out into the room\.

The wide bell helps the low notes come out too\.

### 8. Play a record

Now everything works together: spring, gears, groove, needle, diaphragm and horn\. Press Play to lower the needle onto the spinning record and listen\. Every sound you hear comes from a wiggle in the groove\.