Track on wood expanding/contracting question


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Necrosaro420

Member
Ive been reading on here and there is talk about wood expanding with humidity etc. My base layout is a 4x8 sheet of plywood. If I lay an inch or so of styro on top of that, do I have to worry about the track expanding/contracting etc? If I dont have any parts of the layout on the wood, but all on a sheet of styro?
 
I can give you a few hints on wood. First I like Foam but if you are mounting under layout switch machines this is not an easy task with foam.

One good suggestion on using wood. I bought my lumber from a quality local yard. Had to pay a little more than the Home Depots and Lowes. I took the wood to my basement where my layout was going to be and left it there for about a week and a half so it gets use to the Humidity. Any bad warpage should show at that time.

That is one trick that I have learned from woodworking in general and it should ease your mind a little when using wood for a base. Hope that helps a bit.
 
The track plan and type of rail joints can play a part in track expansion. If the layout is in a climate controlled room, then the problem will probably be minimal. An oval or dogbone plan will more likely experience expand/contract problems than a switching only operation. I have a dogbone layout with tight radius curves in a kinda-climate-controlled shed. The first winter, I cut expansion gaps at several locations in the return loops. That helped. Yesterday, I just repaired a joint that had expanded to a near corner (0-6-0s don't like turns). I'm guessing that a solution would be to use brass rail joiners (not soldered) and a lot of power drops to the buss.
 
As suggested above, if the wood is of quality, allowed to adjust to the conditions in which it will be used for several days (four as a minimum), it should serve well with tracks nailed or caulked to it. But the key is keeping the subsequent, and inevitable, humidity shifts within a 20% range.

Caulking the tracks will be much more forgiving because the caulk is plastic and will help the rail elements to resist movement, especially compression.

You can either cut or provide expansion joints while constructing the tracks. You do this by soldering every other track joiner, but leaving the two joiners on either side of the soldered joiner open and free to slide...thus provinding some accommodation to any swelling or shrinking of the wooden frame members. You can even simply leave gaps and not use joiners. Some prefer to fill such gaps with styrene plugs to help keep the gaps from closing. My response would be that, if at all possible, obviate the need for such plugs by controlling humidity. I only use such plugs when I have inadvertently left a gap that ends up being too wide, often due to improper measuring.

-Crandell
 
Thanks, my layout is in the garage, with a pretty crappy garage door so it lets in alot of weather from outside. Im in KY, so it gets down in the 20 and 30's in winter, and today its 85. I plan on getting a new garage door before winter to help with drafts etc from inside there.
 
Perhaps what you want is either spline roadbed or cookie-cutter supported on risers that will allow more give as the bench elements, with their milled lumber, move under the risers. My track is suspended on MDF splines held up by 1X2 clear spruce risers that are screwed into joists on open frame bench modules. I get zero problems with movement of my rails.

-Crandell
 
I could use that idea. What I was wanting was a double rail around a 4x8 with turnoffs in the mix, and kinda like a valley in between the circle. Hope that makes sense. What would be the best way of doing that? By a "spline" do you mean just kinda like a cut out a couple inches wide to put the track down on with say some 2x4 or something similiar to bring it up in the air more? What I have now is just a framed 4x8 with a 5/8th inch plywood nailed to the top of it.

Also, im laying the track on a roll of cork thats made for under the tracks, will that help combat the wood expanding and pulling the track apart etc?

Im going with a layout based off this:

falls_mill_ho_4x8.gif
 
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By spline I mean laminating up to six 1/4" thick X 15/16" wide X 8' long MDF lengths. You place risers vertically so that they are anchored that way, and with their tops at the grade you want, minus the height of the spline. You place a stout nail at the centerline, driven deep enough to provide resistance and an anchoring around which you bend the MDF lengths. You glue three to each other at a time, staggering their ends by about 3", let them dry and conform to both the grade and curvatures you impose on them by using small clamps of various configurations, and then go back and clamp on another two or three lengths to get the width of roadbed you need.

If you google "spline roadbed", you'll find plenty of sites describing it.

Cookie cutter means using a scroll saw or jig saw to cut the curves into 1/2" - 3/4" plywood. With the right width and lengths joined end-to-end, probably also on risers, you achieve much the same thing.

The trick is always to have a vertical curve into and out of any grades. No kinking or abrupt changes in grade, or your engines will possibly nose out on the rising rails, or the couplers behind the engine can decouple and your train rolls back down the grade. Splines make the vertical curve automatically, and also do easements into curves. Easements on horizontal curves are very important as your curves tighten in radius.

You can derive vertical transitions into grades with cookie-cutter sections by anchoring one end with screws driven flush, and then bending it up so that it sits atop the first riser. Obviously the placement of that first riser is key. The plywood will bend and give you a nice curve, provided you use the right quality of plywood, anchor it sufficiently at the non-grade end, and place the top of the first riser so that your grade is met by that point, and no more.

As a quick observation, you show a river coming from mid-right, under which you will have two tracks? This will necessarily be a very steep water course if you want the clearances you'll need between the rail heights below and whatever carries the water. It gets worse toward the inner curve of rail.

-Crandell
 
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In my experience, plywood expands and contracts very little. You can always seal the plywood with exterior paint or varnish to reduce humidity changes. Just paint both sides and all exposed edges before you start the scenery. The more layers of wood (greater number of plies) you have, the less likely your are to have problems.
 
If I were to cut some layout out of wood and prop it in the air, would using things like 2x4 pieces under the new wood/track hold up well? Say on a 4' straight section, place a 4' pieces of 2x4 down, then place a straight piece of say MDF board on top of it work good and stop expanding/contracting etc? I want to raise the track off the ground some anyways so that I can make a valley to build a town into
 
Here is a an example of my layout using board and "risers" I would suggest using a good quality 5/8 board, not 3/8 . I would also suggest using 1 X dimensional lumber ( ex. 1x4) instead of 2X4. Seems to work for me. The warpage I am having is the areas I used 3/8. I am going to have to reinforce those.

ATTACH]
 
My layout is inside, but in an area where the AC/Heat is minimal most of the year. I live near Houston, so humidity is a fact of life. the room sees mid 60s to mid 80s and every drop of humidity that Houston can offer.... The layout is plywood, purchased at Big Box stores on the cheap or picked up at local construction sites for free. The framing is medium quality or worse 1x2 fir. The wood parts are glued AND screwed together.

some places have foam on top of the plywood, some don't. The roadbed is inexpensive cork glued with wood glue to the foam or plywood. Most of the track is glued and nailed to the cork (to hold it while the glue sets) and in a few places glued (Elmer's Wood Glue) directly to the plywood.

I soldered most of the rail joints, leaving every 3rd (or so) unsoldered with a slight gap (but still using a rail joiner).

I have no kinking or expansion/contraction issues in the 20+ years it has been up.

That being said, I believe that most of the angst about expansion if in the climate controlled portion of your house, is highly overwrought. My details above should prove that, even in doing most things "wrong", I still have no issues with tracks kinking, being misaligned or any other horror stories.
 
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