That's why I use polystyrene foam, cuts easier too.
Had no idea that XPS (Blue foam for me) would shrink with time. I knew temperatures and humidity was an enemy but did not realize that time was another factor. One side of my layout is a 28 ft run of blue foam. Based on the 1/4" per 4 foot info above, that is a 1.75" shrink over time for that 28 ft run. I think I will insert some of the KATO expansion joints at each end of the 8 ft sections. Perhaps that will delay the time for major surgery.
The other factor is how the shrinkge will effect the scenery elements. Has anyone noted cracks in your scenery due to shrinkage of the underlying blue/pink form?
Paul D
N scale Washita and Santa Fe RailroadSouthern Oklahoma circa late 70's
BigDaddy Ken Patterson believes his foam has shrunk over the years. The video is his June 2015 What's Neat. He said it didn't affect the track. 1/4" of shrinkage, I don't see how that's possible
Ken Patterson believes his foam has shrunk over the years. The video is his June 2015 What's Neat. He said it didn't affect the track. 1/4" of shrinkage, I don't see how that's possible
Extruded foam shrinks over time. Well known in the building trades. One of the reasons XPS cannot be used as a vapor barrier. Dow and OC have shrinkage specifications in datasheet. 1/4" across 48" within first few years is typical.
Alan
Freelancing the LK&O Railroad
Henry
COB Potomac & Northern
Shenandoah Valley
If built with the foam on top of open box construction, you will get almost no expantion as wood only expands .01% in the length direction, basicaly nothing. In case you are interested depth is 4% and width is 8%, these are pretty much the max with dried iumber.
As the OP, I am fighting temperatures today. It was 102 today in SE Oklahoma but it was dry. I don't think humidity will be a major problem for me. I have very little wood in my structure plus it is not overly humid as a rule in my area. As I was working on my layout today, I had the A/C working and I could almost hear the elec meter spinning. $$$$$$
As noted earlier, I think controlling the temp will be my primary plan of attack. Perhaps 85 in summer and 45 in winter when I am not in building should help. In addition, I think I will drop in a few of the KATO expansion joint for insurance. If I do not have any problems with those temperatures, I will expand the range a bit.
Thanks for the feedback.
Ultimately, the only hard and fast answer is a climate controlled space. As was noted, the Midwest can be especially bad, because it can have extremes of temp and humidity across the full range of temps. You may never solve a humidity problem through natural ventilation here, dehumidifiers or A/C are typically required.
Other locations and environments vary, so don't give up on other solutions and go straight to A/C. Any reduction you can bring about in the temp and humidity of the air your dehumidification method handles will save on the energy it uses.
Mike Lehman
Urbana, IL
I have an idea that I might want to run with: wire some electrical jumpers between each major section of track that is at risk of expansion/contraction. The real-life railroads do this to help with track grounding in all conditions.
However, in HO scale, it would be extremely difficult to accomplish, so the alternative is to carve some slots into the track bed, and run the jumper wires underneath the tracks, just under the rail ties. This would eliminate the need to directly solder the rail joints together, and thus make it easier for them to flex.
Another idea I'm thinking about running with for my future layout, is using wood planking spaced 1" apart on the layout table, and then putting 2-inch foam on top of that. The planking would be able to shift, but the foam would not be significantly impacted by this.
I also agree with the idea of sealing the wood as someone earlier suggested - make sure you dry the wood first, before doing any finishing on it to prep it for the sealing.
As others indicated, it is more likely the benchwork (esp plywood) will shrink as it dries and cause track warpage. I know from experience.
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
All metals expand with rises in temperature. In the case of nickel-silver rails, very little. An uncut length of Code 100 rail will only expand 0.25" over 100 feet with a rise of 30 deg F. Four 1/16" gaps spread along those 100' will take care of a 30 deg spread. However, the dimensional/milled spruce and pine that we use for frame members does a lot more moving, even over the 10' lengths some of us use for L-girders. It isn't so much along the length, but across the surface, or transversely to the grain, that the wood swells and shrinks with large changes in ambient humidity and moisture content in the wood. If you build your layout with the wood recently off the stack at your lumber yard, and then go to look at your carefully laid curves in mid-July or August, you will probably see your tracks making curves you had never intended, some of them vertical. The milled lumber has shrunk and has brought all the rail metal to a tighter convergence, even closing up all those nice gaps with sliding joiners you left for that purpose. When something has to give, it's the adhesive if you've used that to keep the tracks in place, or the tiny plastic spike heads give and your rails pop out.
Humidity in train rooms should be kept within a range of 40-65% or so. Anything outside of that range invites some serious repairs. I keep a $200 deumidifier in my train room year-round and monitor the humidity digitally with a remote from one of those weather predicting digital panels you can hang on your wall.
mlehman Based on my experience and as I recall the previous discussion cited, essentially don't solder everything together.
Based on my experience and as I recall the previous discussion cited, essentially don't solder everything together.
I smiled when I read the comment about not soldering rail joints.
Years ago, I built an HO scale layout using plywood as my table top.
Being in a hurry to get trains running, I layed the cork and track for the first mainline. A short time later I noticed the curves and some straight sections were bent out of alignment.
It didn't take long to figure out what had happened. The wood had dried out and shrunk.
I now had the same length of track on a shorter piece of wood.
Fortunately, I hadn't soldered any joints. I pulled a few spikes on each side of the joint, marked how much of each rail overlapped, then cut and filed the rails to fit.
Now that the wood had dried out, it was a one-time fix.
I'd also agree with the comments on humidity vs temperature.
Everything I've read and heard from other modelers would indicate that rails expand and contract slightly due to changes in temperature. However, being that the cross section of the rail is fairly small, it shouldn't cause much of an issue as long as there are a few gaps to accommodate the change in length.
The problem with wood is that it expands and contracts with changes in humidity.
Doing what you can to minimize changes in both is always good, but it may be that limiting changes in humidity would do the most for you.
As long as you used just foam and regular track cork and have a slight curve and attach the track with caulk, you should have no problems as long as you are not in direct sunlight. The foam will not expand enough to cause a problem and the cork roadbed because of the way it is made (that is why I said regular track cork wich is made of cheap cork leftovers and a binding agent), dosn't expand much.
IMO it is cheaper to run the heat or A/C, at a minimum setting, rather than to crank the system up when you want to enjoy the hobby room. If you want to enjoy the hobby without all the frustrations of mysterously bad track work, the temp and humidity should be addressed and under control.
Seal the wooden benchwork with paint to help prevent expansion and contraction during the temperature swings. Temparature is not the primary issue, but changes in humidity, associated with temp swings, is a huge factor. Wood will swell and contract with humidity changes affecting the trackwork.
Case in point: My layout is in a heated finished 3/4 walk out basement but no A/C. The temp is comfortable but varies between 65 and 70. The humidity can change from 60 to 80 quickly. Benchwork: pine select 4", 3/4" cabinet grade plywood as the sub-roadbed, homosote roadbed, ME flex track, caulking to secure roadbed and flex, soldered every other rail joiner, FT turnouts NOT soldered on all 3 ends.
I did not seal the wood benchwork and continued to build and lay track. I quickly noticed track problems when the humidity changed. Too late to properly seal the benchwork. I fixed the problems but they returned with the next humidity change; more repairs! I had a problem area that was going to need its third (3rd!) repair due to humidity changes. A dehumidifier was purchased and set up in the hobby room. Within a 1/2 day the humidity had been balanced and stabilized. That troublesome area repaired itself and has not been a problem since.
Based on numerous past topics on this expanstion/contraction, it appears there will be strong disagreement on which is expanding and contracting, the chicken or the egg. Ya'll can crack on and stand your ground - I'm ok with that.
Bottom line is the track is affected - it happened to me in my Bloomington Indiana garage layout, which was not heated or air conditioned. Temperature swings in Bloomington could be as low as zero F and bone dry in the winter, and high 90's in the summer with air so humid, you could cut it with a knife. My track contracted in the winter and many of the solder joints broke free; in the some track was bulging where it had expanded.
Leaving track joints free to "breath" sure seems like part of the answer, but climate control ultimately is the other, more important part.
Rio Grande. The Action Road - Focus 1977-1983
Over 2 years ago, I had to build a new HO layout in a 12' X 24" out building. I insulated, paneled and wired it. The first year i did not have climate control while the layout was being contsructed and it showed. Some of the plywood top warp a little and some of the 2 x 4 legs expanded slightly upward. I installed an AC window unit when that stared to happen and a Kerosene heater for winter. And last October my property got flooded and the train buiding had 4-5 inches of water in it for 5 days. That warped the floor molding and some paneling warped at the bottom, but the layout seem to be unaffected. I try to maintain it at 60-85 degrees with 40-60% humidity to save energy costs.
True, it's the wood that travels farthest. Still have to accomodate the shifts in laying your track.
Based on my experience and as I recall the previous discussion cited, essentially don't solder everything together. Yes, you can still solder many rail joints, but you need to leave ones the slip via a rail joiner connection with a bit of a gap between the butted rail ends.
Hard to say how much over 30'. If generally low humidity, you'll have fewer issues with the same temp swings than you would where the humidity also vary widely, so keep that in mind, too. I'd leave 5 or 6, but that's just because that sounds about right.
No experience with the Kato expansion tracks, but I'd bet they allow for far more movement than you'll need. So long as you leave several of the expansion gaps using rail joiners, the Kato expansion tracks are probably overkill.
There was was a good discussion one year ago about this.
Ray
Contrary to popular belief, the track doesn't expand and contract, the benchwork does .... which makes it appear as though the track is.
Instead of using dimensional lumber to build your benchwork, use quality 3/4" plywood and rip it to create boards from which to construct the frame work. Much more stable in wild temperature changes.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
My N scale layout (under construction) is in an area that can experience seasonal temperatures from below freezing to over 100 in summer. All my previous layouts were built in temperature controlled areas so I never had to deal with temperature extreems. I know it will flex with temperature but how much? Track & turnouts are all Peco code 80 flextrack on cork on a foam base. Longest semi straight (slight curves) run is about 30 feet but also have some pure straight runs of 10 feet in yard area. Am I likely to experience any major problems with track under these circumstances? I am not using Kato track but I do have some of their expansion track sections that I could insert into the straight track sections if needed.
The area does have heat & air but I do not typically have it on unless I am in the area due to cost. If needed, I have the option of maintaining the temperature so that it avoids the extreems. I was hoping to avoid this due to cost but if I can avoid problems by keeping temps controled (between 40 and 90?), I will do it.
Am I overly concerned about this or should I insert several of the Kato expansion track sections as insurance. Am I most likely to experience problems with the extreem cold or heat? I would like your thoughts on when temperatures will jump up and bite me.