Abstract: A hi-rail device for mounting on a vehicle, comprising a locking slot comprising a first locking end and a second locking end, and a locking pin movable in translation within the locking slot and captured therein. The locking slot which is continuous between the first locking end and the second locking end, thereby being confined between the first locking end and the second locking end. A linkage is provided, and is foldable and unfoldable to displace an axle assembly for holding wheels. A spring-extended locking cylinder extends from the linkage to the locking pin, comprising a locking spring to urge the locking pin into the respective abutting surface of any one of the first locking end and the second locking end when the locking pin is in any one of them, thereby using only spring force in extension to lock the linkage into either locking position.