12-31-2010, 05:19 PM
Gary S Wrote:Thanks for the info, tetters. I sure would like to see those photos if you dig them up.
As for different batches of rail having different expansion properties, I think the difference would be close to nil. There isn't much difference in the expansion rates of variouos types of brass alloys. The difference is in the 10 millionths of an inch if I remember the expansion chart correctly.
This track buckling has to be a combination of the wood benchwork shrinking due to drying out, and the expansion of the track due to the heat. I'm not worried a bit about my layout cosnidering its past performance in climate extremes, and now it has a comfy home in the layout building.
From my background around wooden boats, 99% of the problem is very likely the wood drying out and shrinking. Even a 4x8 sheet of plywood will change a 1/4" along its length given the right changes in humidity. Paint retards the flow of moisture in and out of wood, but does not stop the flow. The real value of paint is that it might slow the moisture flow enough to get past a spike or valley in ambient humidity. Leaving the heater on at a higher than normal temp dried the plywood and wood out more than normal, especially if it stayed that way for a few days.
Why did one track buckle and not the other? My guess is the gaps were slightly smaller on the track that buckled than on the other. It would have been an interesting experiment to turn on a humidifier while the temps were elevated (to avoid condensation), and see if the buckling went away.
The power of the expansion and contraction of wood is pretty incredible. Put a wood planked boat (freshly painted) in the water, and you can't believe how fast it is sinking from the water coming in. Pumps can't keep up. 3 days later, it won't leak a drop. OTOH, plank a boat with dry, seasoned wood without steaming the planking. Butt the planks together as hard as you can. Throw it in the water and see how fast the planks pop their fastenings.
just my thoughts and experiences
Fred W