Is a "Helix" a spiral?

I am doing a basement layout plan on the atlas free ware lay out planner. I am wondering if a “Helix” is a spiral for climing mountains. How difficult are they to use on a layout. Are they realistic?

Thanks everyone for there time.

Classypete

A helix is indeed a spiral that model railroaders use to climb between levels. I have about 6 complete spirals in my helix.

Real railroads do occasionally use a helix. They tend to be not much more than a single loop. There is a helix in a tunnel in Canada. Most model railroad helixes are hidden in a mountain or closet.

For a model railroad, a helix enables a multi-deck layout in a reasonable space.

I expect you’ll get a lot more replies and a few pictures from others … a helix is a popular topic!

Marty

A picture before the mountain was built to cover it …

That pic is sooo cool. Thanks. How do you start a helix and what measurements would I use to construct a couple. Is there a specific book for doing helixes…lol. The spiral tunnels are in use by Canadain Pacific and they are on Rogers Pass, in the Rockies.

Thanks again.

Classypete

In my model ralroading, I use both helices and a spiral.

The helices, hidden partially or completely, are circles of constant radius on a steady grade and provide maximum climb with minimum forward progress. Think of the threads on a machine screw - that is a helix.

The spiral is my rolling stock minimum radius test tool. It is a series of curve sectors, of diminishing radii, laid on a plane surface (sheet of plywood.) I’ll start the test with the vehicle (loco, freight car, MU car or whatever) on the wide end - 42 inch radius. How far it gets into the spiral tells me what minimum radius it will accept, and what radius will make it actively unhappy. Most make it to approximately 18 inch radius, some can get to 12 inch radius or less, and one class of diesel MU cars hits the ties at anything under 24 inches.

The closest I can come to picturing a spiral is the threading on the pointy end of a wood screw, but laid out on a plane surface (no grades.)

Hope this helps.

Chuck (modeling Central Japan in September, 1964)

Maybe and probably not are the answers to your questions. Most model railroad helix are coils, not spirals. A spiral gets bigger or smaller as it goes up. A coil remains uniform.

Unless you are doing an open pit mine, there are few if any other uses of helix’ in the prototype. Prototype helix are indeed spirals not coils for reasons that seem obvious to me.

For perhaps the most comprehensive work on Spiral Helix on the web, visit PPUINN’s Blog.

Leave a comment on his blog that Joe Daddy sent you! Dave is a genius.

Joe Daddy

A helix is a three-dimensional curve of less than infinite radius (infinite radius is a straight line) wherein the center of curvature, as you move along the curve, itself moves in space.

A spiral is a curve of ever-decreasing (or increasing) radius.

Most helices on model railroads that I know of are cylindrical, circular helicies - curves of constant radius whose center of curvature moves along a straight (up) line (usually at a constant rate). There are exceptions, and some folks have built conical spiral helices (curves of ever-decreasing radius whose center of curvature moves along a straight (up) line).

The term “helix” is used pretty loosely to describe any helix-like structure designed to get track from one level to the next. My own helix really isn’t one, as it has 24" straight sections every 180 degrees, so there are actually two vertical curve axes spaced 24" apart. But everyone knows what I mean when I call it a helix. There would be some geometrical term for this shape, but I’ve never bothered to figure out what it is.

My “helix” when it was under construction:

FYI

The spiral tunnels are located in Kicking-Horse Pass, not Roger’s Pass.

The best way to figure out how to calculate a spiral is to figure out what the maximum grade % that you want. The spiral tunnels mentioned above are maximum 2.2% grade. So, essentially for every 100 inches of track it will climb 2.2 inches.

The amount of climb needed to provide clearance for the largest rolling stock that will pass between the layers coupled with the limitations of the radius size you can use will decide what grade the helix has to be.

What scale do you model… I’ve already figured out a bunch of radius requirements for N scale if that will help you.