They do _what_ to the train?
Trip Start Sep 04, 2007
19Trip End Nov 20, 2007
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Erlian, China isn't much to write home about. It's a border town in a desert, and if the train didn't go through here, it'd be even more of a nothing. It has one interesting quirk, though. Because Erlian is on the border between Mongolia and China, and because Mongolia and China use different gauges of railway track (the tracks are further apart in Mongolia), they change the wheel assemblies in Erlian.
Hard to believe, but true: they pull rail cars (in pairs, in our case) into a big garage, disconnect each rail car from its wheels, lift the car, roll the wider-set wheels out from under the car and lift the wheels out of the way, roll in narrower-set wheels, lower the rail cars onto the new wheels, and (hopefully) attach each rail car to its new wheels
Not surprisingly, this whole process takes a while. Some of the time required to cross the border was tied up in showing passports to border authorities in two countries, but we spent only about an hour on the Mongolia side of the border, while we spent four hours, more or less, on the China side.
You may be able to learn more at http://en.wikipedia.org/wiki/Trans-Mongolian_Railway, but I'm basing this guess on the summary that is visible in Google.com.cn because I can't view the page. When I try, an error message in Chinese appears. I can't imagine what that might mean.