Hot Rails to Helix

Pfunk Mar 5, 2022

  1. Pfunk

    Pfunk TrainBoard Member

    Reasons to do a helix:
    -Have multiple levels, plenty of space for one
    -Would make layout infinitely more interesting
    -Favorite train has very little stage time with current design

    Reasons not to do a helix:
    -Cost of materials, esp extra track
    -Accessibility for derails
    -Math sucks

    I had originally wanted to do a helix then talked myself out of it. Then someone else mentioned it and now I am in full-blown ping pong brain and trying to weigh the options. I have tons of space, and the only train that would be on it would not have autohaulers or anything at all height-restrictive (this Kato E259 Narita Express, six cars:


    So, a few questions for the pros and those who have built these into their creations....

    1. I am doing the entire layout in Unitrack. I would think Unitrack would be best to use for a helix for reliability, but is that overkill? Could do it in flex for less than half, would need less height clearance with flex on cork than the Unitrack roadbed.
    2. Is it easier to track plan for a single or a double track helix, even for a single train in and out of it? I mean, I have the room. Which leads to...
    3. I have up to 36" I can use, but I think this train would run fine on 24" which would give me more space to track into and out of a helix. I only need to rise about 2, maybe 2-1/2", but given the extra height for the Unitrack I'm curious about radius recommendations.

    And finally...

    4. Why are so many apprehensive of building these things? What am I missing? It seems pretty simple. Involved planning and tedious construction, sure, but not exactly rocket surgery. When I see sponsored YouTubers talk about what a daunting task building a helix is, it makes me worried I am underestimating things.
    BNSF FAN likes this.
  2. Shortround

    Shortround TrainBoard Member

    I have no experience building one. The group I belonged to in the '70s had one 'in the back room and out of sight'. But I think you would need the largest diameter possible. The incline and the radius both add resistance to motion. The engine should be heavy enough for good traction and the cars low weight. Also you will need room to keep those tracks clean for traction and electrical contact. Best wishes.
    I'm not into passenger service but that one you show is cute.
  3. BigJake

    BigJake TrainBoard Member

    BLUF (Bottom Line Up Front): You don't need a helix, for a 2.5" change in elevation.

    1. Helix can transition between levels (>> 2.5") in less space than a more linear ramp.
    1. Around the outside of a 4x4 layout, you only need about 2.5 sides of it to make the 2.5" climb at 2.5% grade.
    2. Helices combine curvature and climb, both of which increase difficulty of both operating and construction.
    3. Hiding a helix while keeping it accessible for maintenance and mishaps is difficult. Many are made large enough so that the user can stand inside them for access. If hidden, you will probably want remote cameras for monitoring trains in the helix.
    4. If you only have 2.5 inches to climb, that's ~8' of climbing trackage to maintain ~2.5% grade. That's a little less than one turn of a 36" diameter helix. In other words, it's not really a helix.
    I would not design a model railroad for only the equipment I currently consider running on it, unless it was closely following a prototype railway. Plan for a variety of equipment, including longer trains and taller railcars (e.g. double-stack containers). Given your Japanese theme, such equipment may be very unlikely though.
    Sumner likes this.
  4. nscalestation

    nscalestation TrainBoard Supporter

    You have mentioned several times that you have plenty of room. If so, do you really need multiple levels ?

    I am building a layout in a 21 x 10 ft space and use the helix to access the staging yards which are underneath the main level. I too was quite apprehensive about building the helix and studied every post and video I could find. I can say now six years after completing the helix that it's worked out really well for me. Quick specs and experiences below.

    • I am using Atlas code 80 flex on cork.
    • The track is not glued down, just a nail every 18-24" to allow for expansion.
    • The overall radius of the helix is 42"
    • The grades are calculated at 2.3% on the outside track and 2.5% on the inside track.
    • The deck is 1/2 inch plywood supported by four pairs of 5/16" all thread rods.
    • The outer edges have 4 vertical supports to hold alignment between levels after a twist was noticed.
    • The space between the decks is 2-3/4" and that has been good access.
    • The max train that will fit in my staging yards and sidings is 14 50ft freight cars and a caboose.
    • A pair of 6 axle or three 4 axle can pull these trains up the helix no problem.

    I chronicled the construction of this helix in my blog, a link to those posts is below.

    If you are modeling Japanese prototype you have a couple of things working for you if you do a helix.

    • Most of the models power units have traction tires so should help with the climb.
    • Train lengths are typically shorter than US prototype.
    Last edited: Mar 5, 2022
    Sumner and BNSF FAN like this.
  5. Sumner

    Sumner TrainBoard Member


    Very innovative, clean and functional way to support the plywood (y).

    Do you run the trains any faster in the helix so the wait is shorter. How long is the wait? Above is that about a 10" to 13" elevation change?

    Going to staging or maybe coming from it do you have the option of shutting the power off in blocks before and after the helix so that you don't have to watch a train that is in it and worry about it coming out one way or the other unattended?

    I have a 12 inch elevation change and have a helix in mind after a lot of looking but want to try something else out first and see it it works.

    BNSF FAN likes this.
  6. Todd Hackett

    Todd Hackett TrainBoard Member

    PFunk - aside from what you have already stated, you might consider the helix as additional serial storage. I am HO Scale and have a 20" between lower and upper level; 4" rise per loop; 5 loops. A 5 track helix with 37" tandem track included makes an oval where there is room for 4 22' trains per loop, or 20 trains. Outside radii is 40", inside 30" with 2.5" track to track separation. Grade on the inside is [ 4 / (( 2 PI * 30") + 74" )] or about 1.5% grade. I plan to use the the center track as run-through, 2 inside as 'down storage' outside 2 for 'up storage'. Also note that my helix is considered a crew change point so you don't have to wait *hours* for your train to reappear. Also note that my helix is under the stairs where pretty much nothing else would really work without head banging.

    Sure, large footprint [ (( PI *43^2 ) + ( 37 * 43 )] or about 7400 square inches. Note that access is built in on the inside. Compare to old-school storage with same capability: [((20*2.0) + 4 )*264] ~ 11,600 inches square. This is 44 inches wide; need at least 18" access on BOTH sides, so 11600 + ( 36 * 264 ) or about 21,000 inches square AND no consideration on switch work to get to all of those tracks. So helix storage is about 1/3rd of parallel storage. If you use 2.5" for center to center the result will be a tad bigger.

    Please check my math as I haven't had coffee yet.
    Pfunk and Sumner like this.
  7. Pfunk

    Pfunk TrainBoard Member

    I decided to redesign my layout plan altogether, was going to be entirely too much trouble for a 1-2 turn helix for such a small rise to begin with. Gives me ideas for the future, but for now I just redid a few things while it's all still on paper instead. Certainly appreciate all the responses!
  8. mrhedley

    mrhedley TrainBoard Member

    With a 5 track helix, trackwork needs to be absolutely perfect. It would be ugly if the moving train on the center track derailed taking out cars on either side. Also, isn't a lot of room for fingers to work, especially if there are cars on either side of the derailed car. But what concerns me most is cleaning the rails, which means you have to vacate the staging tracks for cleaning. I'm assuming you have a fairly long length of mainline on either side of the helix where you can park the cars for cleaning. I have a triple loop, double tracked mainline helix, and keeping the rails clean is difficult, even with a centerline track cleaning car, and no staging of any kind. I'm not suggesting it's impractical, just pointing out the concerns someone should be aware of before building one. If you are using a helix it for staging, I would also suggest putting some window screening around the base to keep cars from falling to the floor, should the worst ever occur, along with some way to access the screening. I did this on hidden curves as well when my layout was 'cookie cutter'. All it takes is an insect carcass you can't see for a small disaster. Don't ask how I know...
    Last edited: Mar 13, 2022

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