Track Shrinkage

[Anonymous]

QUOTE: Originally posted by D_Davis

...And if whay you say is correct and my table top is contracting why are my gaps getting bigger???
.It seems that if the table was contracting the rail would buckle.

There is a little confusion. Yes, if the benchwork was contracting, then the gaps would get smaller, not bigger.

The point that everyone is trying to make is that the metal rails only expand/contract very slightly, and they are only affected by temperature. Wood benchwork will expand and contract more significantly, not only due to temperature, but also due to humidity. If you live in an area that is more humid during the winter than the summer (or if your house's environment is such that it is more humid in the winter than the summer), the benchwork could be expanding due to the humidity. Also, the different pieces of the benchwork might be shifting in different directions, and so even shrinkage might be shifting the trackage in such a way that the gaps are getting bigger, not smaller.

Whatever reason, look to the benchwork as the culprit of practically all of the expansion/contraction.

---jps

[jwar]

Its seems wierd but the above post stateing the wood shrinks and expands is true. From a machinist perspective I thought it was the metal tracks, not realizing wood was in fact the problem.

A friend nailed his track down so good that the expansion of the wood actually moved the track so much he lost four Shinohara Turnouts. He used code 100 track and the weak point was the smaller plastic tie spikes of the turnouts creating the weak point. These were located between two 90 degree crossover tracks, acting like a brick wall forcing the rails to blow out turn outs and even broke some ties in another area. We loosened up the track and let it float, no problems as of this date.

The solution of course is to remove a lot of nails and let the track float sidways as it expands. If you remove or tighten the gaps you will have the opposit problem this summer. If the gaps dont cause problems derailing, perhaps leave them as they are. If there to big cut a small piece of rail and slide into a joiner filling the gap, these could be removed later but that is not a cure for the problem.

Im thinking my problem with movment may be after I glue ballast in and thats a good reason for another post.

From what I have learned from other posts is that the best solution is to lay foam over the layout. The foam will not move as the wood under it expands and contracts.

[Leon Silverman]

One way to avoid gaps is to allow the track to float.
Solder all the rail joints or epoxy them if you need an insulating gap. Spike the rails to the roadbed between the ties. This allows the track move back and forth in response to temperature changes. If you do have a long straightaway, lay it on a gentle curve, instead. That slight curve will either straighten or bend more, ever so slightly, to accomodate the rail length change.
In a curve, the differencial movement can be prevented if the track is anchored at about 1 inch intervals. Otherwise, the nice smoothe curve you laid in the summer will become a series of relatively straight sections between sharp kinks in the track where it is anchored when winter time comes
My experience in this regard involved spiking Atlas flex track to homosote roadbed. I cannot say with certainty that glueing the track to the roadbed would avoid this kinking. I am sure there are some other participants in this forum can comment on this. My guestimate is that you would be ok if either the glue or roadbed has some resiliency in them when the glue dries. Otherwise, cracks or fissures would form.

[Anonymous]

What kind of epoxy will hang in the gaps and not drop out until it sets?? And if
whay you say is correct and my table top is contracting why are my gaps getting bigger???
.It seems that if the table was contracting the rail would buckle.

[cacole]

I agree with orsonroy, your problem is benchwork expansion and contraction with changes in humidity and weather, not track shrinkage.

Several years ago, before we began construction of a 20 x 40 foot HO scale layout with 30-foot long straight sections, we conducted an experiment to determine how much nickel-silver rail expands or contracts with changes in temperature. Two 3-foot pieces of Atlas flex track were placed outside in the Arizona sun on a July afternoon when the air temperature was hovering near 100 degrees. The track became so hot that the crossties became soft. The track's length was measured, and they were then put into a freezer and left overnight. Between 100+ and 0 degrees, both pieces of flextrack shrank less than 1/64th of an inch, or 10/64th of an inch for a 30 foot run. We measured two pieces of track to make sure the measurements were representative. Based on that, we went ahead and laid the track with every other joint soldered, and a feeder wire at every soldered track joint.

As an added precaution, our club layout is built on top of hollow-core luan doors supported by a 2x4 framework, covered with 1 inch of Upson board (sound board), which is a fiber material that is impervious to expansion and contraction. We have had absolutely no problems, even though this layout is in a buidling that has no heating, air conditioning, or insulation, but uses evaporative coolers in the summertime and propane space heaters in the winter. Even these are used only when someone is at the club -- otherwise the inside temperature is colder or hotter than outside, and the humidity fluctuates according to the weather conditions.

[orsonroy]

The track's not shrinking, the benchwork is. Keeping a few unsoldered expansion joints around under these conditions is a good thing. Otherwise, you'll have track popping up all over the place. Drop more feeder wires on the mainlines to ensure a good electricity flow to all sections of the layout. Otherwise, rebuild the layout with a non-shrinking medium like foam board insulation.

[cwclark]

your best bet is to keep the room the same temperature year round...I keep my room at 73 degrees in the summer and the winter...I have an A/C window unit that has a digital temperature control and a space heater with a temperature control and it is also set for 73 degrees ...all my track is soldered at every joint and as long as the room is the same temperature the year round there is no problem...Chuck

[Anonymous]

I set my layout during the summer and now that things are alot cooler, where
I didn't soulder, the gaps are alot bigger. How can this be avouded??? Do
I need to epoxy them?????