Ladies, Gents,
I’d like to present my latest interactive 3D animation of a model vacuum engine. It’s been modelled after a commercially available kit for the “flame-eater”-type engine “Jarne” from Bengs Modellbau, a Germany-based small supplier. This type of engine was never commercially successful and hence has been mostly forgotten. But it still does provide a template for attractive working model engines. See a YT video of the physical «Jarne» in action.
Actually it’s a twin project of building in parallel both the physical model and a virtual model using Three.js. Since I’m not multi-tasking capable, the virtual engine crossed the finish line first.
In terms of Three.js, I followed my trusted workflow of combining Three.js geometries where possible (BoxGeometry, SphereGeometry, LatheGeometry, Tube Geometry, ExtrudeGeometry). More complicated parts,which required some CSG, were modelled in Cinema4D, exported as .vrml files and imported into my animation viewer program.
The animation was written in vanilla Three.js, without any additional libraries. The math for part positions and orientations and joint cohesion is all mine 
. The most challenging part was the computation of the position of the pin, which follows the cam disk groove and controls the rocker arm angle, and ultimately the sliding-door intake valve in the cylinder head. I’ve dedicated an article on my blog to that problem and its solution alone.
renderer.info reports:
calls: 102
lines: 3
points: 0
triangles: 239’784
ToDo: add a visible and animated flame from the alcohol burner in front of the sliding-door intake valve, as well as maybe add a visible outflow of cooled-off gas through the exhaust valve (the little black ball in the top bore of the cylinder head …)
Enjoy!