Onderwagen

Onderwagen is a Dutch term meaning the undercarriage or underbody of a vehicle. It denotes the lower structural assembly that bears the weight of the vehicle and provides support for the wheels or tracks. The word is formed from onder ('under') and wagen ('car' or 'vehicle').

In rail transport, the onderwagen is the bogie: a self-contained wheelset unit consisting of a rigid frame, one or more axles with wheels, suspension elements, and often braking gear. The bogie is connected to the vehicle body by a bolster and suspension, allowing rotation to absorb track irregularities and to improve stability in curves. Bogies can be fixed or swiveling, enabling the wagon, coach, or locomotive to negotiate curves while distributing the vehicle’s load to the rails. They also carry the braking equipment and, in powered bogies, the traction motors.

In other sectors, onderwagen refers to the undercarriage or lower supporting structure of heavy equipment, such as crawler tractors, excavators, or military vehicles. There, the onderwagen includes the frame that carries drive components, the tracks or road wheels, and the suspension. The term emphasizes the lower assembly as distinct from the upper superstructure and is used to describe both the mobility platform and load-bearing elements.

Maintenance and manufacturing contexts use the term to denote modular, replaceable undercarriage units. This modularity facilitates wheelset swaps, suspension work, and braking system maintenance without dismantling the entire vehicle.