Scratch Built Helix on My HO Scale Model Railroad Layout - Design and Build

I’m building a multi-deck HO scale model railroad layout. I'm planning on modeling the Burlington Northern, mostly set in South Dakota in the 1980s. I step through how I designed and built this helix. I share some detail about the role that it will play when we operate this layout someday. Finally, I share a bit about the math that went into engineering the helix, such as calculating the grade. I also note the radius selected and how I arrived at that specification. I go over construction materials and methods as well as touching on the underlying benchwork construction.

Here is some additional discussion about my plans for the upper deck of the BH&E layout. This might be helpful if you aren't familiar with South Dakota's geography:

If you steal this idea from me, you’ve stolen twice. Most of this design came from @JeffJohnston who published an article in the April 2008 Model Railroader and a series of his own YouTube videos:

Reliable Helix Part 1

Reliable Helix Part 2

Chapters:
00:00 Welcome and project introduction
00:33 Acknowledgement to Model Railroader and Jeff Johnston
00:56 Customized the helix for my requirements
01:24 Laying out build requirements, freight car dimensions
02:40 Benchwork construction begins!
03:39 The tabletop / grid overview - crossmembers to attach risers to
04:45 Preparing to set the first turn - an arm to keep the helix round
05:07 2x2 Legs with gussets to support the benchwork
05:36 Using a tramel tool to draw and cut templates on cardboard
06:48 Using birch plywood as roadbed
07:31 Using risers to gain altitude
09:40 Laying the first turn of track on the helix
10:15 Attaching the track to the plywood
10:44 Risers between the turns - 1x4 pine @ 3.5"
11:54 pilot drill and countersink in one tool!
12:28 Deadwood or bust!!!
12:37 A quick discussion of my prototype railroads
14:10 Helix math and engineering - crunching the numbers
15:57 Why did I build this helix before the rest of the railroad?
16:20 Function of the track around the outside of the helix
17:20 Conclusion and some action shots

[avlisk]

I built a helix almost step by step identically to your techniques, so, I can heartily endorse this project. The only real difference for me was I used 27" radius curves with code 83 Atlas track due to space limitations and lots of flex track recycled from a previous layout. That sharp curve hasn't given me any issues in case someone has reservations about it. Just don't go over 2% grade. Beautiful work!

[What_If_We_Tried]

I really appreciate this video, as I only have a small bedroom to build in - approx 8 ft x 12 ft / 2.5 m x 3.7 m - with slopped ceilings starting at 45 in / 114 cm above floor level, and need a 2 level stacked layout, and need a helix to move my trains from one level to the next. * subscribed *

[derekalexander]

You did a really nice job on the helix.

[TwoRailfans]

Nice design and construction. That radius should be great for what you are doing. The less successful examples that I have seen try to do it in too small of a space, but you have a great layout space. I wish we had room for one but we definitely do not!

[achb-railway]

Nice job on the helix. I just built one myself last week - mine is a lot tighter than yours, but it suits the rolling stock I'm using.

[stevedrake]

I may have missed it but what is the diameter of your helix?

[sparky]

thing with a helix, you love them or hate them, you made yours big enough for a double line, why did you only do a single track ?