Overview to Building a Model Railroad Helix

A Helix Is a Real-World Solution

Even a construction as crazy as a helix is not without a counterpart in the real world of railroading. In mountainous regions, elevation changes are accomplished by tracks laid out in long sweeping switchbacks, allowing a gradual track grade to accomplish impressive climbs over long distances. Your model train helix might need to be constructed on a somewhat exaggerated scale, but it is an accurate depiction of real-life engineering solutions.

Planning

Planning is truly the key to a successful helix. Planning in three dimensions can be a challenge as you balance radius, grade, and space. A considerable amount of geometry goes into planning a helix, with several considerations necessary:

• Overall grade. The grade can be defined as the overall rise of your track run divided by the length of the horizontal run, with the product expressed as a percentage. For example, a 3 percent grade would climb three inches for every 100 inches of horizontal length (or about one inch for each 3 1/2 feet). In the real world, the steepest stretch of track grade is operated by short line Madison Railroad, near Madison, Indiana. This track rises 413 feet over a distance of 7,012 feet, which represents a 5.89-percent grade. For model trains, the grade is often increased for convenience, but it still needs to be a convincing replication of real-life conditions.
• Maximum grade. The maximum grade of the rise in your helix track should resemble real-life conditions. In the real world, a 1 1/2 to 2 percent grade is considered steep for heavy freight trains. For short trains pulled by locomotives, such as a passenger sight-seeing train, a 5- to 7-percent maximum grade would appear realistic, and it could even be increased for an especially dramatic look.
• Curve radius. Unlike the grade, which should be the same for any model scale, the curve radius can be tighter with smaller model gauges. Take pains to balance grade and curve radius for a realistic appearance with whatever train gauge you have.
• Transitions. Give careful to incorporate gradual transitions when planning a helix. Transitions that are too sudden can cause uncoupling or derailments. The transition from the helix to level sections of the track must be planned and executed carefully.

Detailed, careful sketches on paper, including dimensions, will help you layout and cut the helix parts efficiently.

Building

While a helix looks complicated, in essence, a helix track layout is really just a curved plywood ramp that begins with a gradual rise and then begins to overlaps itself in one or more sweeping curves. In many designs, the helix ramp itself is made from curved sections of plywood held up by wood pier blocks spaced at regular intervals. The changing heights of the wooden piers holding up the ramp for the initial stretch determines the grade of the helix; the piers also create the tunnel where the track circles over itself as it climbs.

There are also helix designs in which the track ramp sections are attached along their outside edges to long pillars or posts that run from the bottom to the top of the helix rise. With this method, the sections of helix ramp are essentially "hung" onto the posts, much the way that utility shelving is hung from vertical shelving standards.

The biggest challenge in construction is laying out the curved sections of the helix ramp and cutting them accurately, which is usually done with a jigsaw. If you have planned carefully and made accurate drawings, this work will be easier. Assembly of the helix is generally fairly easy, as parts are simply screwed together. Be diligent about making sure the sections of ramp butt together smoothly. Joints should be made directly over wooden piers so they can be anchored securely.

Step-by-step, turn-by-turn, a helix can rise to great heights. Establish a strong base and an even grade on the first tier, and the rest of the helix falls in place quite easily by using support piers of uniform height for the overlapping sections. The gap between the ramp sections must be large enough to allow for easy passage of any train cars that will pass through the tunnel.

As the top of the helix moves past the final curve and back into the straight track, adjust the pier blocking to create a gradual, smooth transition back to a level grade.

Planned carefully, the carpentry involved in building a helix is fairly easy, though it takes time and patience.

Laying Track

Around and around they go. Smooth track is essential to enjoyable operations everywhere, especially in a helix. Lay the track onto the helix ramp sections as you build, carefully securing it before covering the segment over with the next section of tunnel ramp. Low clearances between tiers can make access and maintenance difficult, so it is important to get the tracks right the first time.

Many modelers choose to reinforce the track joints in a helix by soldering as they progress up the helix. Soldering the track both reinforces the joints and improves electrical connectivity. Once the helix is completed, it will be very difficult to perform repairs or adjustments to the tracks, so spending the time soldering is time well invested.

Wiring

Put power in the tower. Wiring your helix is no different than wiring any other track layout, but because many portions of the track will be somewhat inaccessible inside tunnels, you may want to connect more feeders than you would with an exposed track. Some experienced modelers suggest that there should be at least one feeder connection for each tier of the helix. If you make feeder connections only at the top and bottom of the helix, as is often recommended with short tunnels, may eventually lead to connectivity problems.