I read that there are two basic types of hatches seen on covered hoppers, round ones and elongated. The elongated hatches are used primarily for grain loading, while the round ones are mostly for other goods. Plastic pellets, whole grain, and powdered goods all will unload differently, so the type of intended load may influence other parts of the car’s design, such as slope sheet angles, too. Someone more familiar with car design & construction, please speak up.
Bill in FtL