Three wheel sets of a locomotive are powered and can move in horizotal plane to adapt to the curves of the railway.
The green bearings of front and rear wheelsets pivot on the chassis.
The blue bearing of center wheelset can laterally displace thanks to key sliding joint on the grey center inner shaft. Blue and green bearings are connected together by pink sliders.
So when the locomotive enters a railway curve, the front green bearing turns and makes the blue bearing move laterally and the rear green bearing turns in opposite direction.
The grey center inner shaft receives motion from engine via grey gear fixed to the center wheelset and its key sliding joint and transfers the motion to orange front and rear inner shafts via parallelogram mechanisms. Angle between two cranks of each inner shaft differs from 0 and 180 deg. to eliminate dead positions of the parallelogram mechanisms.
The front and rear wheelsets receive motion via pin (in red) slot joints with the orange inner shafts.Thank you Bill Todd for introducing me this interesting design.