I came across this site while searching on information for building a helix. I have to say, this by far the best, elaborate, and detailed explanation that I have been able to come across. If any one is interested in building a helix, do your self a favor and check out this site.
The owner of the site is no longer updating the site for personal reasons, but the information that is there is very in depth.
Thought I would pass it on. Just scroll to the bottom & follow each month of progress.
Here it is: http://www.pcrailroad.org/index.html
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