This article is from ours Department X.
When mechanics put down the pit cover, move the steps out of the way and descend into the black dust of years past, the entrails of an escalator lie before them. The engine that can move many tons of people. And a collection of gears whose worn condition has become a symbol of an entire country: the planetary gear.
The heart of the gearbox is round and about the size of a pizza. At its center is a sun wheel around which planetary gears revolve like a star. So it transfers the power of the electric motor to the main shaft, which moves the steps up, half a meter per second. The planetary gear is a space-saving design, experts rave, but the planetary gear has a problem: If a tooth breaks, the splinters destroy the other gears in a fraction of a second. A total loss for the entire transmission.