At this year’s European Railway Challenge in June 2025 we presented our first locomotive, KARLA. After hours of work, we were able to put KARLA into operation and drive it along the track of Bad Schussenried!
Details on the different subsystems
Sensors
At the front, KARLA features a sensor box containing a LiDAR sensor and an RGB camera that provide environmental data for the automatic train operating system currently under development.
Sensor array at the front, picture by Nils Bernhardt
Drivetrain
KARLA is powered by a PMSM with an integrated absolute encoder. The torque is transmitted to the wheelset via a tooth belt drive.
Battery
KARLA features a removable 24V lithium iron phosphate battery with a capacity of 100 Ah and an integrated battery management system.
Frame
The robust frame made of 40×80S I-type aluminium profiles provides high spatial flexibility for mounting parts.
Braking system
The electric motor brake is used as the service brake, which operates wear-free and recovers energy.
Mechanical piston brakes combined with braking disks from mountain biking serve as the emergency braking system and are automatically engaged by a custom-designed spring-loaded mechanism.
Custom-designed braking module, picture by Nils Bernhardt
Mainboard
The main board houses all electrical components (e.g. CCU, inverter, Wi-Fi router, fuses, and switches). All components are controlled via digital interfaces within a software-defined system.
Overall vehicle concept
Currently, KARLA represents a replicable, individually fully functional bogie unit. By integrating two bogie units into a single main frame, one can build an even more powerful locomotive.
Wheelsets
The wheelsets are connected to the frame via swing arm linkages, with coil shock spring-dampers from mountain biking serving as the primary suspension. The axles are supported in the swing arms by double-row ball bearings.
A fully assembled wheelset, picture by Nils Bernhardt