The invention of steel mold casting by Jacob Mayer (Mühle & Kühne, the predecessor of the Bochum Association) around 1850 made it possible to produce complex shapes and structures that were unattainable with the hitherto conventional methods of forging, turning or milling. This included the casting of steel bells.
Did you know that in Bochum once huge bells were made of cast steel? You can look at the production facility in Westpark at the entrance of the ore railway line. One of the largest and heaviest bells ever produced is located in front of Bochum's town hall and is definitely worth a stop. Incidentally, this is the place to be in the middle of Bochum's city center - one of the best starting points if you want to travel the Erzbahn route.