031+130 (or 0-6-2+2-6-0) <a href="https://en.wikipedia.org/wiki/Gaston_du_Bousquet" class="extiw" title="w:Gaston du Bousquet">Bousquet</a> articulated french steam engine system
model by Pascal Grando
CC BY 2.5
personal picture of a 3D model for realtime simulation