Helix Improvement Project (The Big Dig)

A helix is inside this as of yet treeless mountain. The original track work began to cause problems so I decided to re-do it. Following you will see how I improved the helix.

The helix is built with what I call "stadium seating". The spiral radius increases as it rises. That way I can reach rolling stock easier. The original configuration had a diameter of 29 inches at its smallest (lower most level) increasing to 39 inches at its maximum (top level). There were 3 1/2 turns total. The track was Peco flex laid loose with the rail joints soldered. The plan was that the loose track would allow for expansion and contraction. In reality I found the rail joints began to form a set with a somewhat slight kink. I believe this was due to the expansion of the track and the soldered joints were deforming. As time went on trains began to perform less reliably. The rise, diameter, and deteriorating track work combined to restrict train lengths running through the helix. A solution had to be found!

Here is a closer view of the original track. The spiral was cut from Homosote with stepped riser supports. I made the spirals wide enough to center the track . I studied this setup for quite awhile testing my assortment of engines and rolling stock. I felt two factors contributed to the problem. First the rise was an issue. I needed to find a way to reduce the grade. The second was the kinks forming at the rail joints.

By narrowing the width of the spiral turns (1 1/4 inches) I was able to increase the total turns to 4 1/2 from 3 1/2. This lowered the rise improving the grade. The minimum and maximum radius did not change. I placed the track right at the inside edge of the spiral this time. Because the radius increases I only had to concern myself with clearances on the outside of the curves. With the improvement of the grade I concentrated on eliminating the kinks in the track. Peco track does not want to maintain the curve. Without some way to hold it in place it wants to straighten out. Micro Engineering track on the other hand will stay curved on its own. By switching to ME track less tension would be transferred to the rail joints. This allowed me to not solder the rail joiners. I did run track feeds to each section of flex track to insure conductivity.

This closeup will show the ME flex track glued to the Homosote. Notice how the inside edge of the ties are even with the inside edge of the spiral. You can also see the stepped support and how the spiral radius increases with each level. Gluing the track permanently keeps the curve properly placed on the roadbed.

The rail joints were left unsoldered and gaps in the rail allows for expansion. This system has been operating for about one month and so far has performed faithfully. Eventually the mountain will be covered with trees and access will be only by the hole in the benchwork inside the helix.

I believe my efforts have been rewarded in better operation and recommend this technique to others.