Expansion Gaps

Our club layout has been showing expansion/contraction difficulties (tracks that were straight 2 months ago are now kinked), and I've been wondering
about cutting in expansion gaps. Does anyone have any experience doing this?
I've been thinking a cut at a 45 degree angle would give more support to trains passing by, and allow the gap to be wider than a cut at a 90 degree angle. This is existing trackwork, with problems showing up especially where it has not been ballasted.
Puckdropper
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Puckdropper wrote:

Two months ago -- h'm, sound like the layout's substructure is drying out and shrinking. I assume you're heating the layout room. If the track is too firmly fastened down, it can't give, especially on the curves. So, go around, and pull most of the pins holding the track in place. You need pins only every two feet or so. This looser connection to the roadbed will allow the track to give without kinking. It may develop waves and wiggles, but you'll be able to fix that by pulling the remaining pins, adjusting the wiggle, and putting the pins back in.

Don't cut expansion gaps at 45 degree angles, you'll run the risk of wheels picking the point on the inside of the gap.
The gaps don't need to be air gaps. Stuff a piece of soft styrene into each gap, and glue with a drop of CA. Those plastic closures on bread bags etc are just right for this. File it to shape. You can also use 2-part epoxy to fill the gap. Either will compress enough to prevent kinking of the rail. I would cut such a gap every 6ft or so, closer if there are large variations in humidity. You'll need to run more power feeders, too.

The ballast holds the tie strip firmly in place, and prevents it from moving -- up to a point. If you have too many pin holding the unballasted flex track, it can't ease sideways as the roadbed shrinks, so it tends to kink. This easing happens mostly on the curves, which is where you should have the fewest pins (see above.)
In the long run, as the wood in the layout seasons, the risk of kinking from contraction of the roadbed will diminish to practically nothing.
HTH
--
Wolf Kirchmeir

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Puckdropper wrote:

Do not cut at 45 degree. Cut straight across and fill gap with something that will expand and contract. I used some old blueboard insulation I had. The styrene coffee cup would work too.
Chris
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Thanks to everyone who said not to cut at 45 degrees. I can see where it would cause problems, especially if the expansion of the rail was greater than the gap itself.
Puckdropper
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Puckdropper <puckdropper(at)yahoo(dot)com> wrote:

On a large (400ft main line) HO RR that I helped to build, we discovered just what you have. As the seasons change, so does the size of the wood. Our subroadbed is spline and the roadbed is Vynlbed not cork. I've since used the same construction methods on plywood and cork with excellent results.
A large kink appeared during the first year of mainline construction. Our cure was to cut a gap just as you would for electrical isolation. The gap was surprisingly large, about 1/16 inch for about 40 feet of track. It closed up as the track relaxed. For the rest of the construction we inserted a shim, cut from brass sheet, at each track joint as the track was laid. For each 3 foot section of track we used 10 mils (0.01 inch) in the winter (dry season) and 15 mils in the wet seasons. The shims were removed as the track was glued and weighted so only 1 shim of each thickness was needed.
Track joints were soldered only for very short pieces of track (a couple inches) and all unsoldered joints were jumpered. Rail joiners were not relied upon for electrical conduction. Electrical gaps were cut and stuffed with plastic glued in place with epoxy and carved to rail profile after the epoxy set. All gaps are at 90d to the rail. A slanted gap will force misalignment of he rail if there is any expansion.
There have been no track structure or electrical problems in the 15 years since completion of the main line.
--
Fred Lotte
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Most of the subroadbed appears to be a homosote spline. As things dry, problems with the track occur.

I think the small gap every 3 ft is a good way to go. I'll make sure to pass this suggestion on to the people responsible for the cross-over replacement.

The guideline "every rail should be soldered to something, either another rail or a feeder" is a good one. Glad to see you've had good success with it.

Puckdropper
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Puckdropper wrote:

Happy Holidays Wood expands only along the grain. Meaning a board can not grow longer once it is dried. However as humidity changes, it will become wider or narrower. Metal will expand or shrink depending on temperature. My layout is near my heater. Since its been colder here in Los Angeles the family is running the heater more. My train space is 10 to 15 degree's warmer than when track was layed. The straight runs have taken on a nice wiggle. Lucky for me I'm running shays ,climax's and Heislers so high speed derailments don't happen. The wiggles mimic natural ground movements. HAHAHA Since metal and wood expand and contract at different rates, your best bet is temp. control. Just like when laying flooring, you need to allow all materials to equalize before construction. Then, just keep the temp even throughout the year Thanks Mike M
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On Thu, 25 Dec 2008 14:48:38 -0800, mike mueller wrote:

That's across. not along.

But the above is correct anyway :-).
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Larry Blanchard wrote:

I stand corrected. Yes it should have been across the grain
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Best is to not ever solder lengths of the rail together. Short gaps of about 0.020" or so will usually take care of the expansion problems and won't make for any troubles with the wheels picking at them. If you want to do angled joints, make the angle from the top to bottom at the angle. Easy to cut with a Dremel that way. and the wheels won't have anything to pick at. I'll note taht this is a common problem as many people don't realize how much wood and metal changes in length with temp and humidity.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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"Puckdropper" <puckdropper(at)yahoo(dot)com> wrote in message

A couple of thoughts... I doubt if the rail expands enough to cause serious kinking unless there were extreme temperature changes.. As others have suggested, it is probably the sub roadbed and perhaps even the benchwork itself.
When I built mine, I built the framework from cut plywood then glued luan paneling on that. Next, I glued 3/4" blue foam on that. This technique seems to have minimized the whole expansion issue as I haven't seen any signs of it for at least five years.
As to what to use between rail moints... I'd consider the plastic insulated rail moiners. They are certainly flexible enough to allow for the micro-minimal expansion & contraction that would take place.
Hope this helps...
dlm
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With wood bases, the expansion of the wood with humidity can produce problems if the rails are all soldered together. Best is to lay each section of rail and leave about 0.020 or so between, depending upon the temp and humidity of the wood at the moment. A piecce of cardstock (a business card is a fine measuring stick here) will usually provide enough of a gap to insure no kinking of the track. I handlay all of my track and nevere have had any kinking problems, even on layouts that go through wide temp extremes.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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From what I've read, heard, and seen, it's humidity and not temperature that makes the biggest difference in expansion and contraction. I completely agree about expansion gaps, by its very nature my home layout has them every 4'. (It's modular.)
If you accept that feeders need to be dropped from every piece of rail, there's no reason to buy metal joiners at all.
Puckdropper
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"Puckdropper" <puckdropper(at)yahoo(dot)com> wrote in message

I think I'd still use them, just to keep the rail ends in alignment.
dlm
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With flextrack, I'd use railjoiners but wiht handlaid track, the spikes can be placed anywhere so it doesn't matter if you do use them. Rail joints are usually between two ties in handlaying track and that isn't much of a free end. With flextrack, you may have several ties that don't have good tiedowns so railjoiners are a better bet.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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I've never hand laid track; I was referring to my experience using flex track. But you are correct; if one was to hand lay their track. spike placement could very well eliminate misalligned rail ends.
dlm
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On Mon, 05 Jan 2009 12:32:46 -0500, Dan Merkel wrote:

That is what spikes are invented for. To align ends...
- Groet, salut, Wim.
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As I understand it, spikes were invented to attach the rails to the ties.
*Fishplates*, OTOH, were invented to align the rail ends and hold 'em togerther.
http://en.wikipedia.org/wiki/Fishplate
~Pete
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when you get to scale track, the strength of the rails is a lot higher than with prototype track. As such, fishplates really aren't needed. It would also be a bit difficult to put together track with real working fishplates! Boplts 0.006" in diameter are going to be a bit difficult to work with. I will note that with 7.5" gauge track, you do need to use fishplates to keep the track in alilgnment as the ties are not glued well to the ground and thus the ends of the rails can move about if they are between the ties and it is a bit difficult to spike two rail ends to a single tie.
-- Bob May
rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net
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On Mon, 5 Jan 2009 14:27:02 -0800 (PST), Twibil wrote:

Or here:
http://tinyurl.com/833vpa
--
Steve

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