This was the monster helix I had to build. It's actually single track and connects all 3 levels. It gets trains from staging to both main levels. It is 9 turns and stands 9' tall. 2% grade, 40" outside radius, 38" inside radius. Dave Sommers designed it. This helix runs great.
My first helix. 3 turns. Double track 42" outside radius, 40" inside radius. 2.25% grade.