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Problem With Track Expansion
Andrew asks readers:
“I have a 6×4 foot, HO scale, DC layout with 3 separate tracks. Throughout the hot summer my tracks have expanded under the heat and are taking a while to contract back to the right position. Is there anyone out there who can suggest a way to stop this from happening all together or at least not as severe? “
15 Responses to Problem With Track Expansion
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I’m afraid the only way to deal with this problem is air conditioning. The tracks will expand lineally in their long direction when it gets warm. The track will also grow cross wise, but the growth will not be noticed.
Thanks for this information Jim. Very appreciative.
My HO 2.5m x 1.7m layout is in my garage with heat coming down from the iron roof, no insulation. I left gaps in the track throughout and so far I have not had any of the track twisting like a snake in the extreme heat that we had during summer. I glued the track down too which might also help.
Correction, my layout is 4.5m x 1.7m. Hit the wrong key.
With nickel silver expansion coefficient of 16-17ppm per degree Celsius you would need a very large length of rail to get a significant amount of expansion. As Jim suggested air con is one way to solve the problem, the other is to leave a small expansion gap on each rail joint without soldering the fishplates to the rail.
Basic physics, metals will expand when they get hot.
I have a figure of 19 ppm for nickel -silver, so if you built the layout in your garage in winter at zero degrees C, and summer temperature got to 40 degrees C, a two metre length of track would expand 1.6 mm, enough to cause problems if the rails were tightly end-to-end.
So as Robert says, leave a small gap between the ends of the rails when connecting track sections so it can slide a little in the fish-plate..
But as a really neat bonus, this will also help to provide a more realistic “clickety-clack” sound effect if the rail gaps are prototypically spaced.
Just one more thought:
Are you sure the problem is not also due to the wooden base drying out and shrinking ?
Thermal expansion is a major issue (fact) we have to address in the design of petro-chem plants. The “rule of thumb” is steel will expand at a rate of 13/16 inch per 100 feet of material per 100 degrees F change in temp. Plastic type materials expand at a greater rate, as much as 5 times that of steel.
A single loop of steel rail around a 6×4 ft plan might be around 15 ft long. 15 percent of 13/16 inch is about 1/8 inch. You might expect that much expansion if you get a 100 degree change in temperature (not too difficult to imagine). I would guess brass or nickle-silver would have a larger coefficient of expansion and thus more expansion. I would not expect your rail to straighten itself once it is bent.
We resolve the problem by anchoring pipes at intervals (every 200 ft on long runs) and putting expansion loops in the middle of each set of anchors. We may guide the pipe in the direction of expected expansion but do not otherwise restrict its movement. We consider both changes in ambient temperature and the change in the temperature of the commodity inside the pipe from a cold state to operating temperature. Steam piping temps may be 600 degrees F or higher and these pipes really do grow. Failure to resolve the issue adequately can, and has, resulted in dramatic failures of structures and equipment.
For an imperfect solution in an imperfect situation you might want to consider anchoring your tracks in the middle of the long runs and allowing them to expand into the curves. A dislocation of 1/64 inch in a curve might be manageable. Best to get the expansion rate of your particular track and do the math first. Good luck.
High guys,
Please don’t blame yourself for the expansion issue causing track distortion. If the climate inside your train room is such to cause this problem, it can’t be much good for you either. Insulation and air conditioning are not just for operator comfort, but layout comfort. They also help control dust and humidity which leads to corrosion of metallic parts (electric motors, electronics, wheels and axles).
Real world tracks are now commonly laid in 2 mile welded lengths!
In the same way that you can stretch a steel wire or indeed a steel rail you can also contain it, to a degree, by heavy concrete sleepers. We can’t do that but we can avoid laying our track at very cold temperatures to minimise expansion and contraction problems.
If, as it should be, each section of track is individually wired there is no need to solder any joints. If you have got tightly butted joints and an expansion problem, just make a few gaps with a Dremel diamond disc cutter. If you are worried about the track moving at the cut, use plenty ot Araldite to glue the track in place and cut straight through that too. Weather and track ballast the glue and it will disappear.
Thank you so much for the great ideas and solutions to my problem. Some very interesting thoughts were raised inside my head as I read these replies, so thank you again.
If your layout is outside , bring it indoors. If it is indoors put it a temperature controller room.
That IS YOUR Problem. Where ever you have the layout it is affected by the weather..
Hope this helps you
Don
I find it hard to believe you have a track expansion problem. If it were your track should return to it’s length as soon as the temp goes down. I would look more a humidity issue. If you are working on a wood base it can expand or contract 1″ or more and will take a very long time to recover.
Thanks for the thought. Will look at a way to fix it. If you know of a way I would gladly like to know. Thanks.
If it is humidity there’s probably not much you can do with a finished layout. I build a lot of pine cabinets and have found that by sealing each piece before assembly I eliminate the problem. I’d just fix the track and put in some rail joiners hopefully the problem won’t come back.
On the real railway, they tend to lay the long-welded or continuously welded track in relatively warm weather, so that the usual problem is one of contraction rather than expansion; this puts the rails under considerable tension, but steel has a very high tensile strength, which it is why it is used in pre-stressed concrete structures. The heavy concrete sleepers (“Ties” in North America) and high ballast shoulders keep the track in place (like the concrete in the pre-stressed beams just mentioned). Where significant temperature variation is known to be a problem, we can ensure track is laid at the normal summer temperature and anchor it well with glue & ballast or pins/screws, and solder any joints (e.g. with fishplates). Unfortunately, if you have already laid you track in relatively cold weather, the best you can probably do if you’re experiencing problems is to cut the track into lengths representing the normal fishplated track, so that the effective length of the whole thing is reduced and the changes in length due to expansion & contraction are divided up amongst a large number of small gaps instead of just a couple that open out in cold weather to an extent that interferes with good running. Naturally, you would have to do something to ensure continuity of electrical supply along the tracks by soldering a feed to each rail or by soldering a connecting wire across each gap – one that will flex with any movement in the track. Air conditioning may now begin to sound the more practical solution!