Rotary car dumper

[2] When combined with Janney couplers that were free to rotate, this permitted dumping cars without uncoupling them from the train.

The rotary mine-car dumper offered by the Ottumwa Box-Car Loader Company in 1909 could dump five relatively small mine cars per minute.

[4] The primary alternative to rotary dumping has long been provided by a wide variety of self-unloading cars.

[7][8] All of these have the advantage that they can be unloaded anywhere, but the disadvantage that any imperfection in the seals of the doors allows material to spill onto the track.

[10] In the 19th century, a patent was issued for a machine to tip entire railroad cars endwise for unloading.