Helix!

World's Largest N Scale Helix?

In our last discussion I was ranting on about grades and helixes and what not. The only real way to see if this idea would work was to mock up the beast shown at left using some foam board I had purchased for backdrops. With a 30" minimum radius this massive construct is almost six feet across. You can see that it takes up most of our family room. Fortunately the garage is a tad larger. The wide curves were necessary to produce the 1.6% grade I feel my locomotives can handle. I won't actually know if this is true until I lay track and run a few trains up that slope. My quartet of Baldwin "sharks" are typically assigned a twenty car train on level track. Hopefully they can make it up the hill with the same train.

Allegheny Eastern Track Plan

You can see from the floor plan to the right that the helix is a major component of the layout. The green lines represent the "east slope" of the Alleghenies and the scenery will reflect that. Gallitzin and its helper loop are level trackage and are shown in black. The red lines indicate the west slope (the helix) between Gallitzin and Cresson and points west. On the layout these tracks actually connect to the east end of Altoona and as such represent connections to points east. The helix tracks are long enough to serve double duty as staging tracks, but there is no plan to use them as such. Trains may "hold" on the helix while traffic through Altoona clears the tracks but only temporarily. I know staging is recommended for realistic operation, but I have opted to try another idea. A possible staging solution used on yet another N scale "Horseshoe Curve" based layout can be found in the October 2011 issue of Model Railroad Hobbyist. Currently, I don't see the major difference between staged trains and the "orbiting" trains I'll be using on the Allegheny Eastern. Staging does allow each train to be unique in consist and the use of prototypical consist for a particular train at a given time. Unfortunately, only so many staging tracks can be provided. Either way the layout runs a limited amount of trains per operating session. I want to create the impression of a large number of trains passing over the hill, not necessarily duplicate the exact car and consist of each train.

While reading the July 2011 issue of  Model Railroad Hobbyist, I came across an extensive article on building "helixi". The helix in the article by Art Houston is quite tall. Way back when I thought the All East would be multi-level I could have used it as is. The construction technique can be used for any height helix. I like the idea of the laminated and staggered joints, but the "wastage" caused by using quarter turns of plywood goes against my grain.Still, the article caused me to rethink my own design. The trapezoid panels waste less lumber in one sense because they are straight. On the other hand the design makes them larger than what is actually required to carry the track.

By splitting the loops into ten 36 degree sections I was able to get the entire helix on one 4' x 8' sheet of plywood. I tried smaller trapezoids in several redesigns but wasn't satisfied. Each section still required too much width and required multiple sheets of plywood. I followed Art's idea of curved sections, but stayed with 10 per loop. I was able to get all 20 sections required for the entire helix on one sheet. I wasn't planning on using Art's overlapping joints, however, because the plywood at Home Depot run's about $20 a sheet. Serendipity stepped in at that point...I found the 1/4" plywood underlayment on sale at a local Lowes for about $11 a sheet so the redesigned helix will be laminated with staggered joints. The real helix will cost less than the mockup!

With the laminated panels the helix is 1/2" thick, more than strong enough to support the N scale trains and scenery. There is still 2 1/2" of clearance between loops making it easy to access the track and trains in the event of a derailment or repair. A major cost will be the track itself. The price of code 55 flex track has risen since I started the layout and is now about $4 or so for a 30" section. The four tracks in the helix will require over 100 sections! It might be possible to save money by using code 80 on this part of the layout, but it doesn't look promising. Last I checked the code 80 was just as expensive.