This simulator models a rigid, planar, non-offset slider-crank mechanism — a crankshaft, connecting rod and piston — at a prescribed constant angular speed. Adjust crank radius, rod-length-to-crank-radius ratio, reciprocating mass and an applied axial force, and watch the exact (non-sinusoidal) piston displacement, velocity, acceleration and torque develop through the revolution.
• A real-time 3D cutaway workbench of the crank webs and offset crankpin, split-big-end connecting rod, wrist pin and ringed piston inside a removable cylinder sleeve, plus main-bearing pedestals and a flywheel angle encoder, with home view, focus-selected-part, full-enclosure/cutaway toggle, exploded view, auto-rotate, expand and show/hide labels controls. • An Equipment laboratory tab with a labeled parts index (crankshaft, rod, piston, cylinder, bearings, flywheel, console) and click-to-inspect component callouts, plus a live displacement chart over one crank revolution. • Fixture controls: prescribed crank speed (0–180 rpm), crank radius (20–70 mm), connecting-rod length / crank radius ratio (2.5–5), reciprocating point mass (0.2–3 kg), constant applied downstroke-direction force (0–3000 N) and a draggable crank angle from TDC (0–360°). • Playback controls: pause/resume, 0.1 s and 1 s step, four speeds (10× slow motion, real time, 10× faster, 1 minute per second), plus start/stop, position-at-TDC, position-at-BDC and advance-90° quick actions. • A Curves & measurements tab with two live charts (displacement; velocity and acceleration on dual axes), the underlying model equations (exact slider-crank kinematics, applied and inertial torque) and snapshot measurement readouts for twelve metrics including rod obliquity and net torque. • An Experiments tab with four guided fixtures (top dead center, bottom dead center, shorter connecting rod, double crank speed) and a Model verification bench that runs independent deterministic checks against a fresh model without disturbing your live trial, plus a timestamped event log and a copyable trial report. • A Learn & assess tab with guided lessons, a knowledge-check quiz with reset, and a written model-scope statement with a referenced technical background link.
If the connecting rod were infinitely long, the piston would move sinusoidally with the crank angle. Because the rod has a finite length, its obliquity — the angle it makes with the cylinder axis as the crankpin swings around — distorts that motion. The simulator computes the exact geometry, x = r + l − r·cosθ − √(l² − r²sin²θ), rather than approximating it, so the departure from sinusoidal motion grows visibly as the rod-ratio (l/r) is lowered toward its minimum of 2.5.
Stroke — the distance between top and bottom dead center — stays exactly twice the crank radius regardless of rod length, since it is set purely by the crankpin's circular path, not by rod obliquity.
Instantaneous crank torque from the applied axial force follows virtual work: Tforce = F·(dx/dθ). At either dead center this lever arm is zero, so the applied force produces no crank torque there no matter how large it is. A reciprocating point mass adds its own inertial torque requirement, Tinertia = m·a·(dx/dθ), and net torque is the applied torque minus that inertial term.
This is a kinematic teaching model: it assumes a frictionless, non-offset slider-crank with an externally prescribed constant speed. It does not model rod or crank inertia, side thrust, friction, combustion pressure or thermodynamics — the constant applied force is a teaching load, not a combustion-pressure trace, and an external motor is assumed to supply whatever torque keeps the speed constant.
No. Velocity is zero at a turning point like TDC, but acceleration can be nonzero there — acceleration measures how velocity is changing, and velocity is changing fastest right as it reverses direction.
Stroke equals exactly twice the crank radius (2r), since it is the distance between the two dead-center positions traced by the crankpin's circular path — connecting-rod length does not change it.
A shorter rod (lower rod-ratio l/r) increases rod obliquity, which makes piston motion depart further from a simple sinusoid. The simulator lets you compare a rod ratio of 2.5 against 5 directly on the displacement chart.
No. It is a rigid, frictionless slider-crank kinematic and simplified-inertial-torque model with a constant applied force as a teaching load. It excludes combustion pressure, thermodynamics, rod/crank inertia, side thrust and friction, and no geometry is drawn from a manufacturer engine.