A motorcycle engine of this brand was installed on Frantisek Novak's first helicopter. Both the motorcycles and the engines were known by the name "Torpedo."

- It appears that the engine model was a three-cylinder, 25-hp engine, capable of driving a 3-meter-diameter rotor.

"Novak's Helicopter"

"Trojan & Nagl Engine, Single-Cylinder Torpedo"

- The engine has a simple architecture, notable for its chain-driven magneto drive. Incidentally, it has a protective cover.

- However, on the four-cylinder fan-shape engine, the two magneto chains are exposed to the air.

“4-cylinder fan-shaped engine”

The author is still searching for a three-cylinder engine from 1908-9, which is possibly the one that was used on the helicopter.