# Escalator Anatomy

By Jason Huang

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/Q4pK9xRDO9Og)

## Guide

### 1. An escalator, opened up

Every day you ride on a moving staircase, but its working parts hide under the floor and side panels\. Here the covers are off\. Drag anywhere to turn it and look inside\.

A typical escalator climbs at 30 degrees and moves at about half a metre per second\.

### 2. The truss: a steel bridge

Everything hangs on the truss, a frame of steel beams and diagonal braces\. Like a bridge, it spans from the lower floor to the upper floor and carries the steps, the machine and all the riders\.

This truss is about 1\.1 metres deep, a common size for shopping centre escalators\.

### 3. The motor hides at the top

An electric motor sits in the machine space under the top landing\. A gearbox slows its fast spin, and a chain carries the turning force to the main drive shaft, a steel axle across the escalator\. A brake can hold everything still\.

The brake works automatically if the power fails, so the steps stop safely\.

### 4. Sprockets pull the step chains

The drive shaft turns two toothed wheels called sprockets\. They pull two long loops of chain, one on each side, and every step is fixed to those chains\. Another pair of sprockets at the bottom keeps the chains tight\.

The steps never carry the pull themselves: the chains do the work\.

### 5. Wheels on two tracks

Each step rolls on four wheels running in steel tracks\. The front wheels follow one track, the back wheels follow a second track set a little lower\. That shift keeps every step level, even on the slope\. Lift the steps away to see the bare tracks\.

Where the two tracks come together at each end, the steps flatten out into a floor\.

### 6. One step’s round trip

Follow the glowing step\. At the top it slides under the comb plate, the toothed edge of the floor, and turns over around the sprockets\. Then it rides back down underneath, upside down, ready to come round again\.

Shown about three times faster than a real escalator\.

### 7. The handrail has its own drive

The rubber handrail is one long loop too\. It runs over the glass, dips inside at each end, and is pushed along by a drive wheel near the top\. That wheel is turned from the same main shaft, so your hand moves with your feet\.

Inside the rubber are steel cords that stop the handrail from stretching\.

### 8. Comb plates: the safe ending

At each end the steps slide under a comb plate\. Its teeth fit into the grooves on the steps, so shoes are gently lifted off instead of slipping into a gap\. Then the floor plate covers the machine below\.

Look for the small maker’s mark printed on the top floor plate\.