About this 3D model
I designed a curved slope for the Duplo trains. Now you can build a slope around the corner. Use the start and end slope of Pjotrx (http://www.thingiverse.com/thing:122268) for starting and ending. The curved slope is based on 30° pieces and a radius of 260mm (like original. I haven't tried it yet myself cause I printed just 1 piece yet. Maybe I add a rack system in the future...