Why clamp μ_k below μ_s?

Physically kinetic friction is typically slightly less than static; the UI enforces a small margin so breakaway remains meaningful.

Where is the toothed rod geometry?

Omitted. Real toys use directional catches; here a spring-load accumulator stands in for asymmetric catches.

Woodpecker toy (stick–slip)

Stick–slip sleeve on a rod: static hold, spring loading, then kinetic slip — a qualitative hop cycle.

About this model

The woodpecker toy hops down a rod by alternating static friction (stick) and sliding bursts (slip) as internal springs and gravity load the sleeve. This page implements a compact phase machine with breakaway based on static friction and motion damped by kinetic friction — enough to show the rhythm, not enough to reproduce every experimental trace from tribology papers.

Who it's for: Stick-slip friction demos and nonlinear dynamics outreach.

Key terms

Stick-slip
Static friction
Kinetic friction
Woodpecker toy
Phase model

How it works

A sleeve with dry friction on a rod alternately locks under static friction while an internal spring loads, then slips when the breakaway condition is exceeded — a cartoon of the woodpecker’s hopping cycle, not a detailed multibody model.

Frequently asked questions

Why clamp μ_k below μ_s?: Physically kinetic friction is typically slightly less than static; the UI enforces a small margin so breakaway remains meaningful.
Where is the toothed rod geometry?: Omitted. Real toys use directional catches; here a spring-load accumulator stands in for asymmetric catches.

Continue with similar topics in this category — or all 85 in Classical Mechanics.

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