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Cutaway 4-stroke engine

slice + parameter sweep

Single-cylinder 4-stroke cutaway with cross-sections and a 36-frame crank-angle sweep.

Cutaway 4-stroke engine

What it is

A single-cylinder 4-stroke engine, cut away on the +X face to expose piston, conrod, crankshaft, valves, ports, and spark plug — all sized from real bore/stroke/conrod-length parameters and positioned by slider-crank kinematics at a tunable crankAngle. Each part is colored distinctively: copper-orange piston, gray block + head + crankshaft, blue intake valve, red exhaust valve, yellow spark plug, translucent intake/exhaust ports.

Why visual feedback matters

The cutaway face shows every internal feature at once. Because crankAngle is a parameter, sweeping it 0° → 360° produces an animated crank rotation — the centerpiece GIF below. Per-part coloring also makes the assembly self-explanatory without labels: you can tell what each piece does at a glance.

Screenshots

Engine iso
Iso
Engine oblique
Oblique
Axial section
Axial section
Top down
Top-down
Labeled
Labeled

36-frame crank-angle sweep — piston travels TDC → BDC → TDC as the crank rotates.

Crank-angle sweep

Iteration GIF: this engine shipped to main four times before all the bugs were out. See the essay below for the full story.

Iteration GIF

Parameters

Parameters 7
NameDefaultDescription
bore — mm Cylinder bore diameter.
stroke — mm Piston stroke length.
conrodLength — mm Connecting-rod center-to-center length.
compressionRatio 10 Drives combustion-chamber dome size.
crankAngle 30 ° Piston + conrod position. Sweep this to animate.
intakeValveOpen — Intake valve lift fraction (0..1).
exhaustValveOpen — Exhaust valve lift fraction (0..1).

Try it