Rail Expansion Gaps

Inkaneer Apr 21, 2021

  1. Inkaneer

    Inkaneer TrainBoard Member

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    Here is an excellent video on having expansion gaps between two sections of flex track. Note that the rail joiners are not soldered which allows the rail to expand and contract without causing kinks or pulling the rail from the spikes. He uses a .019" feeler gauge but my calculations indicate that a .015" gap would be sufficient on a 30 inch length of flex. That is .015" on both ends of the flex track.

    Here is the video:

    Perfect rail gaps with N scale flex track on your model railroad layout for better operation - YouTube


    Notice he gaps only one end of the track. There should be a corresponding gap between all track sections.
     
    Last edited: Apr 21, 2021
  2. mtntrainman

    mtntrainman TrainBoard Supporter

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    An old credit card makes perfect track gaps...just sayin...(y)
     
  3. Shortround

    Shortround TrainBoard Member

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    My credit cards are .031". :whistle:
     
  4. MK

    MK TrainBoard Member

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    You must have a higher credit limit! :ROFLMAO:
     
  5. mtntrainman

    mtntrainman TrainBoard Supporter

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    :D:D:LOL::LOL::ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:
     
  6. Shortround

    Shortround TrainBoard Member

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  7. Point353

    Point353 TrainBoard Member

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  8. tehachapifan

    tehachapifan TrainBoard Member

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    My wife has a credit card that says "Gap" right on it! How did they know??
     
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  9. Doug Gosha

    Doug Gosha TrainBoard Member

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    In lieu of a "cutting block", I have always just measured the length and cut the rail a tad short. Works OK.

    Doug
     
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  10. NtheBasement

    NtheBasement TrainBoard Member

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    I'm curious about the gaps. I try to avoid creating them and I solder the rail, except at either end of a duckunder bridge where I need gaps. But I have a room with a stable environment.

    Under what circumstances do you avoid creating them because the benchwork is minimally expanded, versus creating them because the benchwork is going to shrink? Also what do Unittrack people do?
     
  11. mtntrainman

    mtntrainman TrainBoard Supporter

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    My layout is 99.9% Unitrack. Its in a harse environment. Near 0 degrees in winter...100 degrees in the summer. I use latex caulk to attach the track to a plywood base. That being said I have never had Unitrack 'kink' or 'buckle' in the 10 years THERR RV has been up and running. Maybe its the plastic trackbed...I'm not sure. :coffee:
     
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  12. wvgca

    wvgca TrainBoard Member

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    in the real world there is a significant difference in thermal expansion between ordinary dirt and steel rails ...
    when in doubt check the thermal expansion of what YOU used ...
     
  13. Inkaneer

    Inkaneer TrainBoard Member

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    By stable environment do you mean the room is heated and has A/C? If so then all is fine until that first power outage. But Model RR Rule 1 applies so do as you will.

    Paint the benchwork with a good primer/sealer and humidity issues will be nonissues. Expansion/contraction of metals is expressed as a co-efficient, meaning there are two variables involved. One is temperature change the other is the length of the rail. A 36" piece of flex track will expand 36 time the amount a 1" section of track will for the same change in temperature. Unitrack straight track largest piece is 248 mm or 9 3/4 inches long. So each piece will expand/contract approx. 1/4 the distance than a piece of 36" flex track and there is enough "slop" in the design to accommodate it. The downside of Unitrack and all the other similar track is that they are glorified sectional track with all the restrictions as far as curve radii. I use it for a temporary test track but prefer Peco C55 flex and switches for their flexibility and high nickel content.
     
  14. mtntrainman

    mtntrainman TrainBoard Supporter

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    Not true.....:rolleyes:
     
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  15. Doug Gosha

    Doug Gosha TrainBoard Member

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    I've just never worried THAT much about gaps and how big they should be and I've never had a problem with kinks, either with flex or sectional track. And no, my layouts have never been in what you would call controlled environments.

    I think it's just a matter of laying the track and not being TOO careful about getting rail ends butted right up to the next one.

    Doug
     
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  16. tonkphilip

    tonkphilip TrainBoard Member

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    Doug, I agree do not get hung up on the gaps, just do it! Just remember that it is good to have just one bigger gap, so that you get a really loud clickety-clack that everyone will be able to hear! - Tonkphilip
     
  17. NtheBasement

    NtheBasement TrainBoard Member

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    Yes, house has heat and AC. Temp is fairly constant but humidity is drier in winter than summer.

    After you go out of your way to create a gap, do you not solder? If you solder then the gap is pointless, right?

    From observing our wood floor and how the cracks open in the winter, I submit that benchwork, because of temp and humidity, expands and contracts 10X more than the metal rail expands and contracts. So any problems are caused not by rail length change per se but rather by the difference between rail length change and benchwork length change. Does that make sense?

    So suppose there is a regime (cold, dry) where the benchwork is has shrunken all it will shrink. If you lay rail at that point and add a gap, the gap will only widen when the benchwork expands (hot, humid). Gapping then is not necessary. It only makes sense to gap the rail if the benchwork is expanded (when hot/humid), right?
     
  18. Shortround

    Shortround TrainBoard Member

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    The same happens here. So, I agree with your observation. And I wouldn't solder the joints with flex track. Only some of the joined sectional track.
     
  19. MK

    MK TrainBoard Member

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    In a perfect world world that would be the regime. But in the real world, how would you know and guarantee that the day you lay your track it is at the coldest/driest? You only realize that only after it has occurred. :)

    You gap the joints and don't solder them. You solder the feeder to the rails.
     
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  20. Rossford Yard

    Rossford Yard TrainBoard Member

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    I think in N a business card, not a credit card, would be enough space for a gap. I think it's a good idea no matter how stable you think the benchwork or room humidity is.

    Great video, though. His method for fitting in small pieces of track works a lot better than my guess, cut, guess, cut again, then finally, cut too much and have to go find another piece of waste track to fit in there, LOL.
     
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