Pendulum 1 110° · 1.00 m · 1.00 kg
Pendulum 2 150° · 1.00 m · 1.00 kg
3D double pendulum
Two bobs on two light arms, free to swing in any direction. The lower bob loops, flips over the top, and draws a tangled trail in space that never repeats. Start a second pendulum a millimeter away, and within seconds the two go completely different ways. Drag to turn the pendulum in 3D, and scroll or pinch to zoom. The Angle of Pendulum 1 and Pendulum 2, Twist, and Spin set how it is let go. Turn on Twin to start a second pendulum 1 mm away and watch the two drift apart.
How it works
- Open this page and the pendulum is already swinging. Drag the picture to turn it and see the trail from any side.
- Set the Angle of Pendulum 1 and Pendulum 2, Twist, and Spin to choose how it is let go, or pick a favorite such as Steady cone.
- Turn on Twin to start a second pendulum 1 mm away and read how far apart they drift. Then save a PNG.
Free in every direction
An ordinary double pendulum swings in one flat plane. Here each arm can swing in any direction, like a ball on a string. Twist turns the lower arm sideways, and Spin gives the whole pendulum a push around the vertical. Without either, the motion stays flat, just like the classic double pendulum.
Two numbers that stay the same
Gravity pulls straight down, and the arms only pull along their length. So two quantities are conserved: the total energy and the angular momentum around the vertical axis. The readout shows both. Energy stays at 100% until you add Damping.
The butterfly effect
Turn on Twin. A second pendulum starts with its lower arm turned a thousandth of a radian, 1 mm on a 1 m arm. For a few seconds the two move as one. Then the gap grows again and again, and soon they swing in completely different ways. That is chaos: exact laws, but an outcome that depends on the start with impossible precision.
Frequently asked questions
What is a double spherical pendulum?
A double pendulum whose arms can swing in any direction instead of in one plane. Each bob moves on a sphere around the point it hangs from.
Why does Steady cone look so calm?
It starts both arms at exactly the angles where gravity and the turning balance, so they sweep around the vertical at a constant rate. It is one of the few orderly motions this pendulum has.
Does the simulation lose energy?
Not by itself. Without Damping the energy readout stays at 100.0%. The arms are set back to their exact length after every step, so they never stretch.
Can I make it flat?
Yes. Set Twist and Spin to 0 and the pendulum swings in one plane, like the classic double pendulum.
Does this upload anything?
No. The pendulum is drawn on a canvas in your browser. Save downloads a PNG. Edit opens that image in the PictorX editor.
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