A small, heavy-duty wheeled truck designed to slide under the axles of a standard-gauge railcar, allowing it to travel over narrow-gauge tracks. Rather than transloading the freight, the entire standard-gauge car is jacked or ramped onto the rollbocks. This is a historic European system occasionally referenced in specialized North American industrial operations.
The historic mining railroad used a rollbock system to bring mainline coal hoppers directly to the tipple.
Related terms
Gauge
The distance between the inside faces of the two rails, 4 feet 8.5 inches on standard-gauge track.
Bogie
A wheeled chassis or framework attached under a rail vehicle to provide support, suspension, and guidance along the track.
Break of gauge
A location where two railway lines with different track widths meet.