Posted by: Roger | October 16, 2012

Building A Helix

Sunday was a busy day. My friend Paul and I built the first helix that will bring trains up from the Saint Paul (and points east) staging yard. Building a helix is an exercise in tradeoffs. This one has a centerline diameter of 44 inches, and 3 inches between each level. It figures out to 2.17 percent grade. I would have liked a lesser grade, but did not want to increase the diameter or decrease the separation.

A helix can be constructed from a single sheet of plywood with some left to spare.

The photo above shows the sheet of plywood after we drew the one-third-arcs from a pattern, except for the piece I am cutting in the photo below. A strip about 7 inches wide has also been cut from the right side, which will be cut and grooved to provide the uprights.

It took a while to cut the 17 arcs on the band saw as I was trying to be as uniform as I could.

It seemed like it took forever to cut the pieces on the band saw, but it didn’t pay to cut too quickly. While I was cutting out the treads, Paul was busy cutting and fabricating the uprights to hold them together.

Cutting and sanding the edges took the most time.

Each arc is held together with a “biscuit” glued into the grooved ends of each arc.

The perspective is a bit goofy from the wide angle lens. I tried to straighten it as best as I could in Photoshop. I’ll cut the tops of the uprights off after I get it in place and have a better idea of how Mount Jumbo will sit over it.

A little over four hours later, we had a completed helix, including a short section of run-in and run-out at each end. Next up is to build the Missoula/Saint Paul yard module so I can connect the two assemblies.

I really want to thank my friend Paul for the expertise, and for the use of the tools at his boat shop. It would have been a much longer process if I had done it with a jig saw. And a whole lot longer if it weren’t for his knowledge of how to build it.


  1. Nice work, looking forward to seeing updates!

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