Abstract: A railroad car conversion apparatus for hauling a flowable material in an open-topped railroad car having a frame for holding a plurality of bladders, which may depend downwardly from the frame into the railroad car. The frame is adapted to fit on top of the sidewalls of a hopper car, and be readily attached or detached from the railcar. A plurality of bladders, which may be attached directly to this frame for removal therewith, are also attached in such a manner that they may be readily filled with or emptied of a fluid of a particulate, flowable material without requiring the removal of the frame. The conversion apparatus includes an elongate central beam having first and second ends, and a plurality of bladder-connecting devices for releasably attaching a plurality of material-receiving bladders to the central beam.