I don't even understand the question ------------------ Alan The perfect combination - BNSF and N Scale! www.ac-models.com Andersley Western Railroad Alan's American Gallery
Alan, a spiral curve going up hill or down hill, like a helix. In the real world these usually coiled around a mountain, so reached their tightest curve radii near the top. To conserve space, a helix is used on scale layouts which is more like the threads on a bolt, all the same radii all the way up, or down. There is a formula for right and or left, I have it, but have to wait to post it, because I had to scan it. [This message has been edited by watash (edited 06 November 2000).]
