const Axle &get_fixed_axle(unsigned) const;
const BogieArray &get_bogies() const { return bogies; }
const Bogie &get_bogie(unsigned) const;
const Axle &get_fixed_axle(unsigned) const;
const BogieArray &get_bogies() const { return bogies; }
const Bogie &get_bogie(unsigned) const;