In 1994, BRIO released the #33389 Tip Converter accessory for the wooden railway system. It is arguably the most baffling of all the wooden railway products, with a name that does nothing to help people understand what it is or what it's for.
Here's how it works: you move a tipping truck into the center of the mechanism, and then turn the knob on the side. This causes the mechanism to lift the tipping truck into the air and flip it over, as if dumping its contents to the ground below. You then turn the knob to lower the car back into place.
Believe it or not, this accessory is modeled after an actual piece of railroad equipment: the rotary car dumper, or wagon tippler as it's known in the U.K. They do exactly what I just described: rotate the track segment and car together to dump out the car's contents. In a real railroad, these are used with gondola cars rather than hopper cars (what BRIO calls tipping trucks) as the latter have sloped sides and hatches for unloading.
Image credit: Heyl & Patterson Inc, WikiMedia Commons
For more images of rotarty car dumpers, do a Google image search.