Coal Cutting Machine, Coil Steam Generator @museum.de

High in the air and below ground – Lilienthal's inventiveness wasn’t confined to aviation. As a young engineer, he worked for machine factories, travelled throughout Saxony’s mining regions...

... and developed a Coal-Cutting Machine, which made working at the coal face a great deal easier. A horizontally mounted gear wheel connected to a hand crank drives two tubular steel cutters that slice into the rock. They simplify the quarrying or mining process by cutting slots into coal, rock salt or any soft rock.

When he developed this lightweight, manually operated coal-cutting machine, Lilienthal was entering into direct competition with his employer, Carl Hoppe. So he registered the patent under his brother's name and sold it in small numbers. This allowed him to create the foundation for his own company making machinery and steam boilers: the "Otto Lilienthal Maschinen- und Dampfkessel-Fabrik", established 1881.

More than 25 further patents were to follow. Among them were several patents for small steam boilers with a focus on operational safety. Lilienthal’s Coil Steam Generator has a serpentine arrangement of tubular elements rather like what you see on the back of any modern fridge. The enormous increase in surface area means that the heat exchange operates more efficiently, so the boiler takes up less room and is cheap to operate.

Lilienthal hoped that his machines would help small craftsmen and tradesmen to keep pace with the factories of the big industrialists. And in the medium term, the lightweight boilers might even find a use in aviation…

For the time being, however, his aim was to work out the rules governing gliding flight. Alongside his work as an entrepreneur, Lilienthal set about researching the flight of birds and then moved on to designing his first flying apparatuses – for which he applied for additional patents.