Howdy, The cars are spotted in a rotory dumper, coal cars are dumped in a similar fashion. Walthers makes a good kit in HO, haven't seen anything kit-wise for N scale. 2slim
In addition to rotary dumps, I've seen some outfits that use a giant vacuum hose to remove the lightweight woodchips from the cars. Also, some cars had "dump ends". On one end, the top was hinged, so that when the opposite end was tilted upwards, the chips could just slide out on the dump end (kinda like how a dump truck operates). Also, there are woodchip hoppers out there (off the top of my head MP, ATSF, and AN have some) that have hopper bays that can be dumped from underneath. SP also had woodchip gons with bottom operating doors that allowed the car to be unloaded in the same manner.
