For my new layout, the Silverton, Lake City and Northern, I am planning a non-standard helix to climb between decks. My intention is to build an hourglass shape inside of a peninsula. The hourglass adds a few inches of straight track over an oval to accomplish the climb. At the top of the climb, the track will cross over the previous level so that the track can exit at the same coordinates on the plan (x,y+20",z). My intention is to make the curves a somewhat sharp 18" radius. I plan to compensate for this by reducing the grade in the area of the curve and increasing it the straight sections. Important to note, this is an HOn3 layout, with the accompanying shorter trains and lighter cars.
Any thoughts on this plan? Anyone built a helix that isn't exactly a helix?
Edit to reflect the actual planned radius in nonlix.
Oval helizes have been done, for sure. Usually to make the grade lower by making each layer have more track.
22" radius seems awfully tight, even for HOn3. A few simple rules of thumb: Hidden track, includeing a helix, should never be your tightest mainline radius, nor should it be your steepest grade.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker Oval helizes have been done, for sure. Usually to make the grade lower by making each layer have more track. 22" radius seems awfully tight, even for HOn3. A few simple rules of thumb: Hidden track, includeing a helix, should never be your tightest mainline radius, nor should it be your steepest grade. --Randy
Tightest mainline radius is 18" in a couple of spots. All equipment runs on 16.5" radius. The calculations worked out to be a 1.5% grade. Ive corrected the above, the radius was actually 18". I didnt look at the plan before posting and went off of memory. The radius probably could be adjusted to 20". The bend at the middle of the "hour glass" is a 20" radius.
I have a helix on my HO scale standard gauge layout with a 22" radius and 2.62% (uncorrected) grade. Since I model a short line, my trains are short (no more than ten NMRA weighted cars). Even my smallest locos can pull these trains up the helix. You should have no problems with similarly short HOn3 trains on a 1.5% grade helix, even at an 18" radius.
Hornblower