Follow the explanation
Back to the model ↑How the parts work together
Make room beside the intake
At 180°, face A bounds a growing chamber connected to the intake opening. Keep watching A as you turn the shaft: the opening stays put while the chamber moves past it.
Close the opening, shrink the space
At 540°, A is clear of both ports and its chamber is shrinking. A trapped charge would be compressed here. The size readout describes geometry; it does not measure pressure or the amount of gas.
Grow again after ignition
At 720°, A’s chamber is growing again and remains clear of the ports. This is the expansion part of the chosen cycle, after the spark cue near 630°. Combustion, gas pressure, and power are not simulated.
Bring the chamber to exhaust
At 990°, A’s shrinking chamber meets the exhaust opening. Continue through a full 1,080° of shaft travel to bring the marked face back to its starting position. B and C follow the same path at different times.
The main parts
- Two-lobed housing
- The pinched, two-lobed inner wall follows the calculated apex path. In 3D, show the removed cover to compare its bores with the housing. The open cutaway exposes the chamber depth and ports.
- Three faces, three chambers
- A, B, and C identify rotor faces, not fixed places. Each curved flank is derived from the housing’s inward envelope, with a small clearance relief between its apices.
- Offset shaft journal
- The rotor centre rides on a journal offset from the shaft axis. Turn the shaft once: the centre completes one orbit, but the rotor turns only 120°.
- Stationary and internal gears
- The central gear stays fixed; the larger internal gear travels with the rotor. Their tangent pitch circles constrain the 3:1 shaft-to-rotor motion. Visible teeth are schematic, not validated involute profiles.
- Apex seals
- The three tips mark ideal sealing paths along the wall. Real engines also need side and corner seals. This model does not calculate seal contact forces or leakage.
- Peripheral ports and spark
- A chamber is connected when its housing arc overlaps an intake or exhaust opening. That reports a connection, not gas flow direction. The spark marker indicates a chosen ignition moment, not a combustion calculation.