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Track expansion

mountaindog
in Layout Planning & Building
What are you all doing to combat track expansion as the seasons change? I layed On30 Micro engineering code 83 track back in the summer and now after the heat is on in the house I have three areas that have buckled. My sub road bed is spline with 1/2" homosote and then cork roadbed. The track was glued down with latex caulk. All rail joiners are sodered. How often should I have provided cut joints for expansion? I can see where it broke loose from the caulk that the ties have moved over an 1/8". I assume its the rail itself that is expanding????

Comments

  • Dave_SDave_S
    What part of the country do you live in?
    While living back in the Chicago area we experienced the problem you describe during our hot humid summers. Usually in fall and winter things dried out considerably and everything would go back close to normal. Try running a dehumidifier round the clock and see if it has a positive effect. Homosote acts like a wick, maybe even more so than lumber.
    As far as gaps, we gapped our rail, roadbed and spline every 5'-6'. As long as you are running jumpers every 5'-6' that might help ease things a bit.

    Later, Dave S Tucson, AZ The Heart of the Sonoran Desert
  • mountaindog
    I'm in south central PA. Pretty much the same here weather wise, hot humid in the summer, dry in the winter. The spline road bed was made from rips of 1/4" underlayment plywood. Supposed to be ultra stable. So the homosote is probably the problem???
  • KCSTrainsKCSTrains
    I'm with Dave. I try to create a gap at each turnout to compensate for the expansion. It happens in Texas as well. Phil
  • vinceg
    Unless you have really large temperature swings in the railroad room, the rail isn't expanding, the roadbed is shrinking. I'm in the Chicago area and had this problem as well -- I think I successfully did just about everything wrong you can think of (you learn by making mistakes and I want to be really smart :-)). The wood/particle board/homasote dries out in winter and gets measurably smaller. The nickel silver rails can't shrink with it and so it eventually pops free of the caulk or forms severe S-curves if you have track nailed down such as in a staging or visible yard. I have found the best defense to be:

    1. Use roadbed materials that are most dimensionally stable such as high-quality furniture-grade plywood . Ideally let it season in your basement for a few months if you can -- can be very moist if you get a fresh batch from the lumber yard. If you ever had a hardwood floor installed you will see that the carpenter will let the planks sit unwrapped for a while in the house before installing. I also have some spline roadbed but I used pine lath (1/4" x 1 1/8") that sat for a while. Works pretty well. Particle board does not work well (surprised me as I thought the high glue content would have made it somewhat more resistant to expansion/contraction). Homasote is not very good. Pine shelving or pine dimensional lumber is exceptionally bad (I did this with my first staging yard and quickly saw horrible results). Another good option for splines is tempered hardboard. Not immune to dimension changes but since it comes in thin strips and you use a healthy dose of wood glue to bind them together, the result ends up being pretty stable. Some people swear by extruded foam because it rejects water well. However, even that has a number of unhappy user stories as the foam can contract over time (material aging and outgassing, I assume, not because of moisture).

    2. Leave gaps for the track to move. Don't solder rail joiners except on curves. Leave a small gap on each of your straight sections so that when the roadbed does start to move around your rails can slide in and out within the joiners. If you have already soldered everything, go back and use a Dremel cutoff disc to put gaps in every 5' or so (but avoid the curves if you can). This means you'll need more feeder wires as well but if you want reliable electrical performance for the long run, this is a good practice, anyway.
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