VEHICLE MECHANISM · ORIGINAL 3D STUDY
If only one stroke makes power, what keeps an engine turning?
Four strokes. One power stroke.
Start with the narrated walkthrough.
See the whole mechanism, then inspect it yourself below.
Take it apart and inspect every system.
Click a part to highlight it and read why it matters.
A familiar object. A hidden system.
Four strokes. One power stroke.
The piston repeats its journey. The valves change the job.
Open one simplified petrol engine to follow the piston, crank linkage and valve drive. The interactive assembly stays at rest while you inspect it or separate its parts.
Four strokes complete one cycle. Valve timing and rotational inertia keep their jobs coordinated.
Read the explanation
A rigid rod joins two different journeys.The piston travels along the cylinder. Its pin connects to a rod whose other end follows the crankshaft. Together they link back-and-forth movement with rotation. This view shows the linkage at rest, with surrounding material ghosted for inspection.
The valves distinguish intake from exhaust.In the simplified cycle, the intake valve admits a fresh charge, both valves close for compression and power, and the exhaust valve opens to let spent gases leave. The head casting is ghosted so you can inspect both valves and their seats. Both valves are seated in this static view; no gas is shown passing through them.
Burning gas pushes. Rotating inertia carries the cycle on.After compression, a spark starts combustion and expanding gas pushes the piston down. The flywheel stores rotational energy and helps carry the engine between power strokes. No ignition, pressure trace or running engine is simulated here.
Two crank turns for one cam turn.This overhead-cam layout uses a toothed belt to link the crankshaft and camshaft. The 20-tooth crank pulley drives a 40-tooth cam pulley, giving one cam revolution per four-stroke cycle. The belt and springs stay at rest here because their flexible deformation is outside this model’s scope.
Sources and safety
- NASA Glenn Research Center: A four-stroke cycle has intake, compression, power and exhaust strokes.
- Briggs & Stratton: A four-stroke cycle takes two crankshaft revolutions; flywheel inertia helps carry motion between power strokes.
- US patent publication US6223713B1: An overhead camshaft can operate valves through direct followers while a timing belt links it to the crankshaft.
Engines involve hot surfaces, fuel, ignition electricity and moving parts. This is not a repair, timing adjustment, fuel experiment or operating procedure. Follow the equipment manual and use qualified service. Never run a combustion engine indoors or in an enclosed space.
Scope and limitations
Original simplified single-cylinder, two-valve, spark-ignition engine with a belt-driven overhead camshaft and direct bucket followers. Not a product replica, complete vehicle engine, calibrated simulation or service model.
- Original single-cylinder belt-driven SOHC/direct-bucket educational engine; no imported CAD, textures, product dimensions or manufacturer replica.
- Idealized non-overlapping four-stroke timing. Two crank revolutions per cam revolution. Not a pressure, combustion, lubrication, performance, emissions, calibration or safety simulation.
- Inspected X=0 portions and removable covers are the conserved original parts; rest assembly and exploded assembly use identical geometry.
- The interactive model provides rest-pose inspection and a continuous parts explosion. It does not animate the coupled belt, springs, valve lift or combustion cycle.
- Illustrative timing omits valve overlap and ignition advance. Fuel delivery, lubrication internals, cooling airflow and ignition electronics are outside this lesson.
- Dimensions, clearances and materials are illustrative rather than specifications for a particular engine.
A four-stroke cycle has intake, compression, power and exhaust strokes.Applies to: Original simplified single-cylinder, two-valve, spark-ignition engine with a belt-driven overhead camshaft and direct bucket followers. Not a product replica, complete vehicle engine, calibrated simulation or service model. Uncertainty: The model uses simplified non-overlapping valve timing and does not calculate real pressure, heat loss or combustion.
A four-stroke cycle takes two crankshaft revolutions; flywheel inertia helps carry motion between power strokes.Applies to: Original simplified single-cylinder, two-valve, spark-ignition engine with a belt-driven overhead camshaft and direct bucket followers. Not a product replica, complete vehicle engine, calibrated simulation or service model. Uncertainty: The flywheel is represented, but rotational speed, stored energy and torque are not calculated.
An overhead camshaft can operate valves through direct followers while a timing belt links it to the crankshaft.Applies to: Original simplified single-cylinder, two-valve, spark-ignition engine with a belt-driven overhead camshaft and direct bucket followers. Not a product replica, complete vehicle engine, calibrated simulation or service model. Uncertainty: The displayed dimensions, 20:40 pulley geometry and separate head are original teaching choices, not a reproduction of the patent.
