I have a 15x13 N-scale ‘L’ shaped layout in the garage, in Riverside Ca. I cut a few expansion gaps in the rail as I laid track when it was 40-50 outside temp. I new the rail would expand in the heat but how much will the wood expand? All benchwork and subroadbed is plywood. It has been in the 80’s here the last few days and the rail gaps are only slightly closed. It will soon be over 90 for the next four or five months with plenty of 100 degree days.
I did have some expansion problems on a smaller layout but I soldered all joints and left no gaps.
It would be nice if I could estimate the expansion per foot of track.
It would also be nice to figure expansion per square foot of wood.
Thanks in advance, also it gets a little hunid here but not too bad.
Your wood expansion should be minimal in comparison to the metal rail growth you have already encountered. If your rail gaps close up entirelyuse care in re-establishing them since they will become larger as fall and your mild winter temperatures return and the rail contracts very slightly to its as laid size.
The plywood should be very stable in dimensionally, unless it gets inundated with a torential rain storm fully soaking the layout. That should be unlikely.
Perhaps one of our “engineers” can suggest an exact formula for the amount of growth you can calculate. However, I suspect that the overall expansion/contraction should be a minimal problem, but one that you may want to “watch” (ie. be aware of if control or signaling systems act up)and make minor adjustments for.
Usually, it’s not the track you have to watch for, it’s the wood. Not so much for temperature change but for moisture. Temp. delta (ie change) for brass (which is what nickle-silver is) and for wood is minimal for only a 50 degree difference. However, if you’re going from under-30% humidity to 99% humidity, the wood will move quite a bit, certainly more than just temperature.
This happened in my club, and despite all the benchwork guys swearing up and down that the wood was fine, it was the track that was moving…it was the wood. Why? Because track was laid during the summer (room temp. 75 degrees with the A/C), and buckled when winter came around (room temp 60 degrees). The humidity, however, went from 80% in the summer to under 30% in the winter. Hmmm…
The expansion problems our club has experienced come from turning on the lighting all day; in our improperly laid sections (no gaps) the rails will kink quite a bit after a few hours under the heat.
Building a gymnasium during springtime, I had the relationship between a steel 100" tape and the truss layout change by about 1 inch between a warm sunny day and a cold cloudy day. It was enough to prevent each run of plywood decking from breaking properly on the trusses across the full run, a sheet had to be cut about every 75 feet.
I agree with the earlier poster, thermal steel expansion/contraction is negligible as copared with moisture contraction/expansion in dimensional lumber.
I just packed my books this morning or I could tell you what the expansion would be. Seriously. It is not as great as a lot of people think. Consider your hot water piping. Does it kink going from say 50 something to 130 something? How about your engine’s exhaust?
Okay, I looked it up on the net - novel idea what!? I do not know the exact alloy. Steel is about 0.0012 millimeters per meter and nickel is about 0.0013 millimeters per meter, per degree Centigrade. So, for a 100 degree Centigrade change (which is huge; equals 180 degrees F) the expansion is 0.13 millimeters per meter. For a 60 degree F change over about 30 feet, the expansion is 0.15 millimeters. Less than the thickness of a business card for reference.
It’s the wood that can be a problem, as it expands at a greatly different rate, and is affected by moisture too. BUT, it’s not the HUGE problem it is made out to be either. Crappy trackwork is somewhat independent of temperature and moisture.
If I recall correctly, wood expands and contracts more as a function of humidity than temperature, so sealing it helps. Metals expand and contract as a function of temperature.
Brass and nickel-silver are not really the same thing. Brass is an alloy of copper and zinc, with a few other elements, mainly tin, lead, and aluminum, added for different attributes. Nickel silver is mainly nickel and copper, and may or may not contain zinc.
Sorry to be a smartie. While 100 degrees Celcius does equal 212 degrees Farenheit, a change of 100ºC is “only” 180ºF.
In the metric system water freezes at 0 degrees. Not so in the US system. It freezes at 32ºF.
I am not so smart. I had to look up whether it is 32 or 36 degrees. Too long since I used the Farenheit scale.
When I went to school, and steam was still king, we had £s, shillings and pence. If something was priced at £2/6/3 and you bought 6 of them, what would the total be? (£13/17/6 I think - long time since I tried that).[sigh]
In the States you have always had logical currency, so why still use inches feet etc? Thanks for bringing back memories of the horrors of non-metric systems.
Where did you get 212 degrees? [:D] Gads. Soon as I saw it in the cold light of day today I changed it before I even saw your post. Thanks. Never object to someone correcting a mistake.
We got to the moon drinking caffienated coffee, smoking cigarettes, and using feet and inches. Now we can’t get off the launch pad 70% of the time, never ON time, and when we do there is a lot of suspense about wheter the astronauts will make it back in one piece. This is progress? We live longer, but most are brainpower diminished the whole extra time.
From reviewing other threads and books, seems like another way to plan for this problem is to not solder straight track joints, i.e. just join with rail joiners without soldering (no way getting around soldering curves using flextrack). Just leaving a minimal amount of gap at the straight-joiners apparently is enough to allow for expansion/contraction in most instances.
It is not the actual humidity that causes the changes in wood, but the change in humidity. Wood, especially lumber, absorbs and gives off moisture in an effort to reach equilibrium with its environment. Therefore, significant swings in humidity induce visible changes in the size of wood.
An extreme example is a wood planked boat. If the boat has been out of the water for a few months the wood’s moisture content has been reduced - especially in northern cold climates, where even though the relative humidity may be high the absolute moisture content is low. When the boat is put back in the water, it leaks terribly for the first few hours. Then the wood starts absorbing moisture and swells back to its intended size, sealing the hull into a watertight unit.
You can also see the effect in wood furniture joints inside a heated house in cold climates without any humidification in the heating system. Forced air heat is the worst for this. Obviously, the shrinking of the wood is not due to temperature (the house is heated) but to a lack of moisture in the air.
Painting, shellacing, sealing all significantly reduce the rate of moisture transferrance into and out of wood, but all sides must be treated or the effect will be even worse - uneven expansion of the wood due to changes in moisture content is called warping.
The other cure is to maintain a relatively constant humidity level through air conditioning (dehumidifies when on) or dehumidifiers during warm humnid weather, and humidifiers when heat is on. This also makes the layout space a more comfortable place to be.
I learned early to have one good-sized dehumidifier standing somewhere nearby in my basement…where my layout sits. Airconditioning would be a waste of money where I live on the ocean. I heat with a wood stove in the winter, and find that the stove cannot cope with the humidity that comes through the basement brick walls, sealed on the outside though they be, due to the frequent and enduring storms that la***he coast during the months from October through March. There is just too much moisture in the sandy soil, and it finds its way into our basement.
As Fred said, wood responds to changes in humidity by shrinking or expanding, and it is this action that can cause misalignments. If you want to control the changes, control the humidity with a dehumidifier set on med-low. Or, if it will allow, keep the humidity between 60 and 66%, ideally.
Wow, I definately don’t have the problems you do. I guess a basement has its pros and cons. Space with water issues to worry about. I dont think I could spend so much time and money in a basement where it could easily get damaged from humidity or flooding. Here on the west coast of the US we dont have basement for the most part. They are rare and hard to find, but if I were to look for a house again I may look for a basement, as I dont think we would have the water problems you have. Although I dont know that for a fact.
I found out the hard way how much plywood can expand. I do most of my model railroading in the fall and winter. I laid the plywood for my urban area in the spring before doing the summer hiatus from the hobby. When I returned in the fall, I discovered that the plywood which I had laid so tightly in the spring had expanded and buckled during the humid summer months. I had to take several types of saws to cut expansion joints between the sheets. As I layout my urban area, I am going to be fully aware of this expansion when laying out my streets and buildings to allow the them to float with the expanding plywood. Otherwise I might return in the fall to discover I have recreated a miniature earthquake.
If you live in an area of high humididity and are not able to control the climate, I would consider sealing the benchwork. Sealing the lumber prior to use is much more convienient and less messy. Shellac or shellac based products actually work best to seal out moisture. Shellac and denatured alcohol will cost much more than a basic primer or house paint, but anything is better than none at all.
I do many pine tongue and groove ceilings and whenever it is to be stained, I will always back prime w/ thinned shellac. This is done whether the ceiling is in a heated interior , exterior porches,3 season rooms or enclosed deck/ patio. Doing this has stopped many proplems w/ the cupping and possible buckling of the wood.
It is very easy to take the dimensioal lumber for the benchwork,and roll the sealer while on saw horses instead of doing the painting after construction.
Bob K.
Virginian:
The reason why you never see hot water or automobile exhaust pipes kink is because they are mounted on supports that allow them to move while the supports remain stationary. Either the support is flexible (automobile) or the pipe is supported by a metal strap (hot water pipe) that allows the pipe to move back and forth.
Train layouts, because the track is either spiked or nailed in place, does not allow for differential movement. When tracks are glued in place the glue is able to to absorb the stress generated by the temperature change up to a point without letting go.
Another solution is to avoid long perfectly straight runs. If you use flextrack and deflect the center of the track by only one inch when it is put down, this should provide enough flecibility to handle any temperature/humidity changes. The deflection will either go down to zero or increase beyond the original 1 inch offset without the track kinking.