Last Spring I laid all the track for my 9' x 9' HO layout. The entire table is built of plywood including the joist structure supporting the top. I used Woodland Scenics foam trackbed and Micro Engineering code 83 track glued down with Aleene's Tacky Glue. Mainline curves are mostly 2' radius with tighter curves on sidings.
When I got back home after a four month absence, I noticed that some of the track had separated from the trackbed and some of the trackbed had separated from the plywood. This only occurred on curved sections and it was the outside rail that seemed to lift up, giving the appearance of a steeply banked curve. This problem only occurred on the long runs on the outside perimeter of the 9' x 9' table.
There is no de-humidifier in the basement or air-conditioning. Since I was not home I don't know how warm it got or how humid.
I don't know if I have a moisture problem or a track temperature/expansion problem. All rail joints are soldered and there are no expansion gaps. Since the table is 100% plywood, I doubt that it experienced any expansion. I live in NJ where there could be a 40 degree temperature change between Spring and Summer in my basement.
I plan to reglue the track and roadbed with Liquid Nails foamboard adhesive which I suspect would be more moisture resistant than the Tacky Glue. I wonder if I should cut some expansion gaps in the NS rail in the straight sections leading up to the curves?
Any suggestions would be helpful and appreciated.
jack
Putting a few expansion joints in wouldn't hurt. Would eliminate track expansion or slight wood movement as a cause of future problems. Second ARTHILL's suggestion, caulk works great and relatively easy to take up roadbed or track should the need arise.
It may actually have been drying and its resultant longitudinal shrinking that caused the tracks to have to bow outward on the curves. Wetter conditions would have caused expansion and the curved tracks would have wanted to straighten or to separate at the joints to keep their purchase on the expanding surfaces below them. Just a thought.
In any event, humidity should be restricted to a fairly narrow range, with extremes of temps being less critical. I have a dehumidifier running year round to control humidity coming up from the un-sealed concrete floor in the basement. I empty 8-10 liters from the receptable every two days during the summer. When I am away and must turn the system off, I often have track problems for the first 24 hours until 60% humidity is restored and the wood returns to its preferred size. In one case, but during high heat when burning wood in the wood stove right next to the layout, a thoroughly hidden section of flex lived up to its name and wowed out of radius by nearly 1 full inch. I don't know if that was due to the MDF spline shrinking with moisture loss or the rails expanding. I cut gaps, though, and have not had a recurrence.
So, if you can stabliize the setting from the point of view of humidity primarily, and then force the track back into place easily, I would use caulking and some track nails and weights until the caulk held and I could remove the other items. BTW, my wowing took place on unballasted track since it was hidden. I have yet to experience such problems on properly ballasted track.
Edited
Selector wrote-It may actually have been drying and its resultant longitudinal shrinking that caused the tracks to have to bow outward on the curves. Wetter conditions would have cause expansion and the tracks would have wanted to straighten or to separate at the joints to keep their purchase on the expanding surfaces below them. Just a thought.
That's what happened to mine over the summer. We had a long hot dry spell and my wood dried out and shrank. Caused kinks on most of my curves. I had to go through and put gaps in all of them. Now that it's cooling off and getting humid, all the gaps are starting to open up. It's a pain not having the $$$ for heat and AC.
loathar wrote: That's what happened to mine over the summer. We had a long hot dry spell and my wood dried out and shrank. Caused kinks on most of my curves. I had to go through and put gaps in all of them. Now that it's cooling off and getting humid, all the gaps are starting to open up. It's a pain not having the $$$ for heat and AC.
You probably don't need heat and AC, but you do need to paint or seal plywood on both sides to prevent changes in humidity from affecting it. It will expand and contract with changes in humidity, despite the way it is glued together from cross laminations. I have had a sheet of half-inch plywood shrink as much as 1/4 inch per 8 feet as it dried out.
jjsjjs wrote:Last Spring I laid all the track for my 9' x 9' HO layout. The entire table is built of plywood including the joist structure supporting the top. I used Woodland Scenics foam trackbed and Micro Engineering code 83 track glued down with Aleene's Tacky Glue. Mainline curves are mostly 2' radius with tighter curves on sidings.
I never heard of Aleene's Tacky Glue. Sectional track (Snap track) and flex track tie strips are made of a fairly slippery plastic and it may be the the Tacky Glue isn't sticking to the tie strips. I use a weatherstrip/caulking compound called "Phenoseal" from a builders supply house. Home Depot or Lowes probably also carries it. Comes in tubes for use with a caulking gun. It sticks well to slippery plastic ties. Dries clear and is nearly invisible.
David Starr www.newsnorthwoods.blogspot.com