TwinDaddy66 wrote:Wow...this got scientific! (LOL) Good info. Which now raises another question....Those of you that do leave "expansion gaps" between rail sections, how much gap are you leaving and not having any problems?Thanks again!
Wow...this got scientific! (LOL) Good info. Which now raises another question....
Those of you that do leave "expansion gaps" between rail sections, how much gap are you leaving and not having any problems?
Thanks again!
The thickness of a diamond cutoff wheel in a dremel tool. I find the regular abrasive wheels a bit too thick. About every 8 feet. I solder all curves, some straights (2 out of 3 joints) and then cut extra extra gaps where I think they might be needed. Offset gaps a few inches on curves if you can. Just a thought - curves in flextrack will take up some of the expansion/contraction, at least when caulked to WS foam roadbed.
Karl
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selector wrote:You should have about 1/16" of space every 3-6'. That means 1/32" gap on each end of a three foot section of flextrack, or about the thickness of an NMRA track gauge....close enough.
We're in the same ballpark - I allow 1mm/meter for expansion per 30 degrees (F) of anticipated change. When the temperature reached 120F during August my rail joints were snug but nothing popped. Now (at 55F+- pre-dawn) they've opened up, but not enough to cause any tracking problems.
Since my benchwork is steel, I don't have any humidity problems there. Likewise, my roadbed is styrofoam, another product which shrugs off humidity changes. All I have to contend with is the 90 degree (F) difference between January pre-dawn and August mid-afternoon temperatures. But the biggest reason for lack of humidity problems is lack of humidity. Here in the dessicated desert humidity in the double digits is a newsworthy event.
IIRC, Tony Koester also learned about differential expansion (and track buckling) the hard way recently. There was a photo in his MR column.
Chuck (modeling Central Japan in September, 1964)
I too am concerned about high humidity on the "wet coast".
I asked about expansion/contraction a few weeks back in some posts. I have not had the new layout up and running through several seasons, but this is what I have done to ward off bad effects:
I had put my track on MDF so contacted Sierrapine in Oregon about their product. They said, "Standard MDF has a LE (linear expansion, I imagine) of about 0.25%. So an 8 foot panel will grow about 0.240" if the humidity went from 50 to 80%." That's enough movement of a small enough change in humidity to cause a lot of shifting.
I did not solder the rail joiners, so there is lots of movement possible. Just used lot and lots of drop feeders. Spiked the flex track sparingly. Weather stipped all train room doors very well. No humidity enters from the rainy weather.
Read in a signmakers forum that a trick with MDF is to seal it with glue, so I "painted" the edges and surfaces of the MDF with a 50-50 carpenter's glue/alcohol & water solution. Also, I had all the 1" MDF panels sitting in the construction room for some weeks before putting track on them.
Got a thermometer and two hygrometers right away and established a base level of temp and humidity at the time of layout construction in the train room. Right now these conditions are pretty moderate. If need be I can turn on a dehumidifier in the train room.
Turned on the heat to reduce relative interior humidity and let it rise up the stairs and away from the room.
As the layout is in the basement, If I keep it warm and dry in the winter I will be ok because the summer temps do not get high in the basement. And here on the "wet coast" winter drying is not a problem like the interior climate zones.
Cross my fingers and keep my eye on the dials.
John, I learned all this also about a year ago. Thought my track was pretty good, and it was, til the wooden benchwork expanded a teeny tiny bit. Oh man, there was a couple of places the track must've went BOIIIIING!
Now when I lay track I leave a little gap. Heck, I kinda like that clickety clack clickety clack sound. :)
Jarrell
selector wrote: Everything expands in response to rises in temperature, even if measured in microns. Rails of the type we use expand, but it might be as much as 1/8" over 8-10' of soldered rail...not very much, since that amounts to 1/16 at each end.
Everything expands in response to rises in temperature, even if measured in microns. Rails of the type we use expand, but it might be as much as 1/8" over 8-10' of soldered rail...not very much, since that amounts to 1/16 at each end.
I just did a quick bit of research, and found that a ten foot section will expand by almost exactly 0.1 inch over a change of 90 degrees F (pretty close to selectors number). That's a bit more than I expected, but I found the same coefficient in a few places, so for now, I'll believe it. That means that the advice to leave a business card's width at an unsoldered joint every 10 feet or so should be pretty good. Especially considering we don't usually lay our track at the extremes. The scary part is, that it one end is stuck down, and the other end can't move out, it has to go up 4 inches to accomodate even that small change (if my geometry with no pencil is good). Of course everything else is expanding too, but at different rates, so figuring out what will really happen is a bit of a guess. Again, the thing to remember is that things will move, and we have to allow for it.
Jeff But it's a dry heat!
When absorptive materials, like wood, become more humid, their individual cells and the interstitial spaces between the cellular material expand. In all directions. This expansion will tend to pull track segments away from each other, so simply joinered gaps will get wider.
Imagine a lump of bread dough with raisins mixed uniformly in it. As the bread rises, it expands in all directions, pulling each raisin away from all the others uniformly. That is what is happening, but on the plane of the surface, on your wooden bench.
As the wood types shrink when humidity reduces, those same gaps will close, perhaps even to the point where they close right up tight and the rails continue to compress along their lengths. Eventually, with no room to permit a containment of the compression, the rails will quickly deflect and bow sideways to accommodate the compression. The deflection is just that, an accommodation. Path of least resistance and all that stuff. Like ice in a frozen bottle, it finds the weakest part of the glass and...bang!
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I guess that makes sense now..if the benchwork contracts, it will squeeze the track closer together making the bulges.....got it.
Thanks
John
Vail and Southwestern RR wrote: My (unproven) belief is that the track is most likely not the thing that expands and contracts (the most), but rather everything else. Especially wood with humidity involved. So I guess I'd say I agree with Zandoz.Everything is going to move, the trick is to figure out how to manage the movement. Once I've figured that out, I'll be rich, and I'll let you know!
My (unproven) belief is that the track is most likely not the thing that expands and contracts (the most), but rather everything else. Especially wood with humidity involved. So I guess I'd say I agree with Zandoz.
Everything is going to move, the trick is to figure out how to manage the movement. Once I've figured that out, I'll be rich, and I'll let you know!
My time and budget expand and contract in inverse to one another! Heated basement, dehumidifier, and storing the supplies in the basement before construction of the subroadbed is my overall strategy. Also, the windows in the basement will never be opened in my lifetime! Climate control! Try that with a garden railroad! You should read about what those folks have to deal with.
Reality...an interesting concept with no successful applications, that should always be accompanied by a "Do not try this at home" warning.
Hundreds of years from now, it will not matter what my bank account was, the sort of house I lived in, or the kind of car I drove...But the world may be different because I did something so bafflingly crazy that my ruins become a tourist attraction.
"Oooh...ahhhh...that's how this all starts...but then there's running...and screaming..."
Guys, I'm confused. I've read about track expansion during hot weather or high humidity where the track expands and buckles. We have had some really wet and cold weather the last few days here in northern Virginia. I went to the basement today and there was a section of straight track buckled up about an inch or so. The buckled section even pulled out the track nails. I thought it was supposed to be the other way around....heat makes buckle...cold makes shrinking...whats up?
Thanks,