TrainNut said:The HO layout at the San Diego Model Railroad museum does. It's quite impressive and I believe they do it without a helix. I'd post you a link but my search engine is not working at the moment. They just opened the second floor for guests recently.
Russ Bellinis said:It is the La Mesa club modeling Tehachapie, and they don't use a helix except the Tehachapie Loop which of couse is a prototype version of a helix.
60103 said:I think one of the clubs in the Kitchener area has a barn full of track that goes on several floors.
WRMRC Website said:Incidentally, cars rolling down a helix result in speeds of up to mach-2 when they finally empty out onto the lower approaches.