# Dilema in my setup regarding wood expansion…



## MoSeS_1592 (Dec 16, 2019)

Hey all, I need some advice with my setup, specifically regarding how to adhere my track directly to pine wood rail in a tricky location...

I’m building an HO scale setup in my basement. It’s an L-shaped setup with a reversing trolley car that runs in both directions. The track will run along the wall up by the ceiling with an about 1/2” car clearance from the ceiling and the track will be offset from the wall so the train cars will have about a half-inch clearance from the wall. There will be 12-feet of straight track, then a 90-degree bend with 15-inch radius curve, then another 12 feet of straight track until it terminates. 

I have 1.5” x .75” x 8’ pine wood rails mounted with metal braces to the wall. This is what the track will sit on. There will be a divide in one of the straight sections where a plastic truss bridge will be installed but that’s beside the point. Anyways, given the location of the wood rails the track will mount to, I need to pre-solder the rail joiners to the straight sections of track BEFORE placing the track up on the wood rail, otherwise there will be no way to get the solder in the correct spot on the outside surface of the rail where it won’t impinge on the wheels. This is no problem. My dilemma however is once the track is soldered and properly positioned, what is the best way to adhere the track to the wood rail?

I can’t use nails because there is no clearance to pound them in, plus the wood will expand and possibly pull the nails out or distort the track. I did leave gaps where the wood rails join together and engage the wall/bridge, etc, to allow for expansion of the wood. 

Given this setup what is the best way to secure the track? Can I use a small bead of wood glue to adhere the track to the wood rail? Will wood expansion distort the track over time if the track is wood-glued to the wood rail it sits on? Should I instead consider installing say, 1mm tall rails along the sides of the wood rails such that the track isn’t adhered at all, but is essentially sitting in a ‘slot’ where it can slide passively to avoid distortion from wood expansion/contraction? I am using nickel plated 36” flex track for the straight sections and rigid 15-inch curve-radius pieces for the 90-degree curve. I would VERY much like to use the wood glue option as it would by far be the easiest but I’m worried the wood expansion over time will break the glue seal on the track or distort it. 
Perhaps I am grossly overestimating the effect of wood expansion. 

FYI, I already have the wood rails and metal braces mounted, and part of this extends over a built-in shelf in our wall, so I don’t have an option to lower the wood rail to make room for, say, a layer of cork board between the track and the wood rail. 

Please advise! Thanks!


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## Tom_C (Jan 8, 2016)

Is the space conditioned, or is the basement unfinished or damp? If it's conditioned I doubt there is going to be enough expansion to cause any problems.

Silicon caulk works well, and it may allow a little movement. If you're really worried about it you could do the slot thing, that should work too.


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## wvgca (Jan 21, 2013)

actually the coeffecient of expansion of the track is probably double what the wood is ...as it gets warmer the track will expand more ..


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## Lehigh74 (Sep 25, 2015)

I would seal the wood with polyurethane or alkyd-based paint. That will stabilize the wood and minimize seasonal expansion/contraction. That would also eliminate the option to use wood glue, but I don’t think wood glue will work well to secure plastic ties to the wood. Some folks use latex caulk or Loctite Powergrip to secure HO track in place. You cold also try double stick tape or hot melt glue.


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## MoSeS_1592 (Dec 16, 2019)

wvgca said:


> actually the coeffecient of expansion of the track is probably double what the wood is ...as it gets warmer the track will expand more ..


You mean the metal rails expanding, yes? I assume if the plastic ties are adhered to the wood then in theory the metal rails will be able to slide a bit within the ties themselves?


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## Dennis461 (Jan 5, 2018)

velcro...
Glue (or self adhesive) to track before putting it up.
Glue to pine boards.


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## MoSeS_1592 (Dec 16, 2019)

Dennis461 said:


> velcro...
> Glue (or self adhesive) to track before putting it up.
> Glue to pine boards.


Interesting idea! I'll look into that.


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## MoSeS_1592 (Dec 16, 2019)

While browsing velcro options I came across Gorilla double sided "tough and clear" mounting tape. I may give this a try and report back how it turns out. 

Thank you for all the advice!


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## DonR (Oct 18, 2012)

You mention that you are building a trolley
layout. The trolley will go from one end to the
other and then reverse. There are special devices
available to control your trolley. Also, such may require
special wiring. Before you attach your track be sure
to check the reversing device wiring requirements.

Don


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## MoSeS_1592 (Dec 16, 2019)

DonR said:


> You mention that you are building a trolley
> layout. The trolley will go from one end to the
> other and then reverse. There are special devices
> available to control your trolley. Also, such may require
> ...


I am going to use an Arduino UNO microcontroller with a relay board and reed switches to take care of the reversing. I like that option because the timing and delays are very customisable, plus I'm going to use the UNO to control the red/green dwarf signal lights at each terminus and also blinking lights i will install on the truss bridge.

Side note: I did a project a while back with an UNO, a photo transistor, and a micro RC steering servo. I retrofitted the servo onto a model crossing gate and had the photo transistors sense the approaching and departing train. The servo drops/raises the gate at a speed similar to a real crossing gate (per YouTube video search haha), and used the PWM feature to fade and pulsate the red flashing LEDS on the gate so the effect was that of a traditional incandescent light with the flash timing matched to that of a real crossing signal.


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## CTValleyRR (Jul 26, 2014)

wvgca said:


> actually the coeffecient of expansion of the track is probably double what the wood is ...as it gets warmer the track will expand more ..


It isn't temperature that makes the wood expand, but humidity, which varies directly with temperature. 28 feet of nickel silver rail expands about 0.0025" with a 10 degree F change in temperature. That's hardly worth bothering about.

Untreated wood, on the other hand, can swell or shrink significantly with a 10% change in relative humidity. Unless your basement is going to have temperature swings of more than 100 degrees, you can forget about rail expansion. Seal the wood with an oil-based finish or with polyurethane, and you won't have any trouble.

You could fasten your track down with glue or adhesive caulk, or you could even set the track into the wet polyurethane, which will act as a glue.


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## mesenteria (Oct 29, 2015)

wvgca said:


> actually the coeffecient of expansion of the track is probably double what the wood is ...as it gets warmer the track will expand more ..


Not in my experience, and not empirically. The tracks will expand in length, while the wood will expand across the grain. Code 100 N/S track will expand only 0.25" over 100' with a rise of 30 deg F. Wood kiln dried and with less than 40% humidity when dimensionally cut and joined will swell at least half an inch over 30' with a rise to 85% humidity. It's worse with lumber, whereas good quality 6+ ply plywood will is much more stable due to the cross-grain laminations.

Often the problem appears that rails will buckle and form a raised arc, or an S curve some place. When this happens, the humid wood has dried too much and has shrunk along the axis of the rails.

You have to pick a short range of humidity when you build and store things on your layout. I use 50% +/- 15%. I can almost hear creaking when it gets down to 35%, and fear wood splitting. On the other hand, here in the PNW, we often run over 90% in the winter months. I have to run a dehumidifier between October and late April.


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## mesenteria (Oct 29, 2015)

MoSeS_1592 said:


> You mean the metal rails expanding, yes? I assume if the plastic ties are adhered to the wood then in theory the metal rails will be able to slide a bit within the ties themselves?


It's not the rails sliding so much as their ends abutting. When there's no room left at a joint, and the rail ends are hard againt each other already, something else has to accommodate the expanding rails. But it's minor...about 0.25" in Code 100 nickel-silver over 100 feet with a rise of 30 deg F. Two or three 1/16" gaps here and there on a layout's tangent rails will help to deal with that.

Some of us leave several unsoldered joiners in place with a noticeable gap between the rail ends along tangents so that rails can close when the drier months happen and we don't run a humidifier...or want to.


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## MoSeS_1592 (Dec 16, 2019)

Thanks for all the great info. Given what has been discussed I think I am going to try using some double sided tape to adhere the track. Each track Terminus will be 1/2 inch from each wall so there will be some room for expansion if need be. On the off-chance the wood expands too much all that will happen is the track will simply loosen from the tape and nothing will get damaged. Fortunately I'm not worried about the cosmetics because the track itself and the top of the wood rail will be hidden from sight because it's so high up towards the ceiling. Where the curve is my plan is to let that part of the track just sit passively on the wooden rail, that way there's room for expansion if the track needs to expand or the wood wants to expand. I used varathane wood stain and also left 1/8" gaps between the wood rail planks to allow for expansion. Again, thanks for all the good advice, it's very much appreciated!


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## MoSeS_1592 (Dec 16, 2019)

For reference I have completed my project and it came out great. I ended up using 3M/Scotch transparent double-sided adhesive mounting squares spaced roughly 12 inches apart and it worked out perfectly. The squares are about 1mm thick so the track sits off of the wood a bit which I believe helps with muffling the sound a bit. The pads are invisible, allow for expansion/contraction of the wood, and if I ever need to service something I can get a flathead screwdriver and hair drier (hot air) and cleanly pull the track off of the adhesive square to lift it, reposition a section, etc.


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## Mark VerMurlen (Aug 15, 2015)

Good to hear you found a solution that's working well for you. Happy railroading!


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