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Every Mechanism

Home How a Gyroscope Works

The wheel that won’t fall over

How a gyroscope works

A spinning wheel holds its direction. Push it, and it swings sideways instead of falling.

Make it precess
A brass gyroscope on a dark slate museum table: the gold rotor spins inside two chrome rings on a curved stand, its axle seen end-on; a toy gyroscope circles on its little tower in front, and lit display cases glow in the dark hall behind.
The gyroscope and the toy on the museum table at the end of the video.
1,500rpm
the rotor’s spin, from three pulls of a cord
75%
of its 2.6 kg sits in the rim
1.42kg·m²/s
of angular momentum
4.2°/s
precession with a 100 g weight

Video

How a Gyroscope Works - Spin That Holds Its Direction

Watch on YouTube

3D model · cut open · 360°

Spin it, weigh it, push it

Pull the cord, hang a weight and watch it swing. Drag to turn, scroll to zoom, click any part.

Try itPull the cord to spin the rotor, then hang the weight.
Loading the 3D model…
Weight

Meet the parts

Twelve parts on the table

The gyroscope taken apart, with the toy beside it. Tap a part or pick a name.

The parts of a gyroscope laid out on a pale table: the cast-iron stand with its curved arm, the outer and inner chrome rings, the brass rotor on its steel axle, the toy gyroscope on its tower; in front, the cord with its wooden toggle, two brass hook weights, two caging screws and a ball bearing.

Hover or tap the picture. Rings mark every part.

Parts diagram

Cut in half

The rotor, its bearings and the inner ring sawn through, so you can see inside. Numbers run from the spin outward.

The gyroscope seen from the front with its front half cut away: the brass rotor's red cut face shows its thick rim, thin web and hub on the steel axle; a ball bearing sits in each brass boss at the axle's ends, inside the inner ring; the outer ring, the curved stand arm, the column, the angle scale and the round cast-iron base are whole; a 100 g weight hangs from the right-hand eyelet.
    How it works, step by step

    Thirty steps, from a toy to a space station

    The video’s steps, each with a moment from it. Show me in 3D sets the model up.

      The toy gyroscope circling its tower in front of the brass gyroscope.
      Step 1 of 30

      A wheel that won’t fall

        Demo · how fast it swings

        Set the precession speed

        Precession speed = twist ÷ angular momentum. A heavier weight swings it faster; a faster spin swings it slower.

        The video’s cases
        –twist from the weight
        –angular momentum
        –precession speed
        –one full circle

        Demo · which way it swings

        The spin arrow chases the twist

        Curl your right fingers with the spin: your thumb is the spin arrow. Do the same for the twist. The spin arrow swings toward the twist arrow.

        Spin
        Weight

        Demo · feel it yourself

        A spinning wheel on a swivel stool

        Tilt the wheel up and the stool turns you the other way; level it and you stop. The spin pointing up and your turn always cancel.

        –the wheel’s spin
        –spin pointing up
        –you turn
        –you have turned

        More to know

        Kinds, history and care

        Six kinds of gyroscope

        Gimballed gyroscopeA rotor in two rings, like this one.
        GyrocompassFinds true north on ships.
        Aircraft instrumentsHold the horizon and the heading.
        Reaction wheels and CMGsTurn spacecraft without fuel.
        MEMS chipA vibrating silicon mass, in every phone.
        Optical gyroscopeLight racing round a loop; no moving parts.

        From a turning Earth to your pocket

        1. Bohnenberger builds a spinning ball in gimbals.
        2. Foucault names it the gyroscope.
        3. Sperry’s gyrocompass goes to sea.
        4. A pilot flies blind on gyro instruments.
        5. The first ring laser gyroscope.
        6. Hubble launches with reaction wheels.
        7. Gyroscope chips arrive in phones.

        Using one well

        • Lock the rings with the caging screws before you pull the cord.
        • Pull hard and straight, in one smooth stroke.
        • Keep fingers off the rim: it moves at 12 m/s.
        • Keep the bearings clean, with only a drop of light oil.

        Things worth knowing

        A heavy rim75 % of the mass, 93 % of the spin’s inertia.
        One circle in 86 sWith 100 g at 1,500 rpm.
        “Turn watcher”What gyroscope means in Greek.
        42 km/h rimThe brass rim’s speed at 1,500 rpm.
        Hubble’s slow turnAbout 90° in 15 minutes.
        Station steering98 kg wheels at 6,600 rpm.
        Quick check

        Four questions