Track expansion & warping

W

Woodie

Active Member
Mar 23, 2001
2,093
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36
Northern Rivers NSW Australia
Guys,

My "shed" is just bout ready for moving in to. :):) It's been fully insulated (fibreglass 'batts") and lined with 3 ply (walls and ceiling) and painted a nice pale "sky blue". It has a concrete floor.

Layout will be about about 30 feet long, by 4 feet wide (bent into a "U" shape.

I'll be using Peco code 75 flexitrack and Peco turnouts. Peco "track joiners", and soldered where necessary.

It can get pretty hot, and pretty cold round here. (no snow), but tonight, for instance will be quite a heavy frost. Clear, still nights, and we get a good frost. (-5C)

Summer? well, can get around the 40C (105F +) mark quite often.

My "shed" is not heated, or air conditioned, but is shaded from afternoon onwards.

Now for the question. :D

Should I need to "gap" the track allowing for expansion when it's hot etc? If so, how often and how far between gaps, and how big should the gap be?

Track will be fixed with track nails (minimum usage), and ballasted. Using cork roadbed.

I don't want it going like:

cwerri-buckle.jpg
 
Hi Woodie,
I live on Cape Cod MA where the temp & humidity swings from 40 to 80 degrees (F) & 25% to 85% in my basement from winter thru summer. I calculated the gap required for that temperatyure swiing to be 1 mil per foot. I cut the track during the cooler weather and measured the thickness of the cutting wheel to determine the distance. I think it was a 10 foot interval. I offset the cut between rails. Take care, Jim
 
I too cut gaps about every 6 ft. Now the only problem I ever had prior to cutting gaps is where I didn't do a thorough job of ballasting. I have tested a 30 ft. section properly ballasted and no gaps and the glued ballast was strong enough to hold expansion in check. I have since gapped this section just in case
 
I have HO flex track 8 foot long soldered together that were ran through a 4 foot tunnel. I didn't ballast the tunnel area. If you lay down and look in the tunnel the track sometimes squiggles when I turn off the cooling back there to save $. When it gets back to 70 it straightens back out, but even at just 90 it's just noticable to the eye; the train has no problems transversing it. So I leave it alone. The modules where it's all ballasted don't show no problems, but the max. module is 8 foot so they are in fact gapped ever 8 foot anyway. But the tunnel showed me that if the track is unballasted that 8 foot is really too long an area. And I second the heating cooling question. You guys must be tuffer than us North Americans, I can't stand it 90 back there. Fred
 
Woodie, I have gapped on curves but only after the ballast is firmly in place. If the track goes a bit out of line use a pair of pliers to gently bring it back in place.
 
Woodie
Living in Arizona temps go from cold nights in winter (35) to summer highs of 120+ (hi temp in train room last year before AC was 128) did not gap rails but lain track when room was in the 90's had no problems with track :)
 
With no climate control, how the heck are you going to work out there??
You guys must be tough!!!!

Cid, you have got to remember one thing--these are railroad workers here. Tough bunch. Can you imagine laying all that track with one guy on these layouts? They don't grow em like that anymore. We pick up cars single handed too. Ha ha.

Sorry, that was sick, but had to throw it in.

All have a nice evening. Jack.

P.S. Obviously, I don't have the quotes down yet. Working on it. Came out, but no blue background.
 
Matthyro said:
Woodie, I have gapped on curves but only after the ballast is firmly in place. If the track goes a bit out of line use a pair of pliers to gently bring it back in place.
Click to expand...

Yeah. Why I asked, is that the last layout, I had joins on a curve (not staggered) and even though the track was ballasted, it did have a slight kink in it that I couldn't easily straighten out, so if I gapped it, on a curve, then the kink could be really bad.
 
If you find it necassary to put a gap on a curve, something to be avoided if possible, before cutting the gap drill small holes (like #72) thru the ties on both sides of both rails on both sides of the gap and spike. This assuming your roadbed will hold spikes. And ballasting before gapping is good too. Or spike alongside the tie, right next to the gap. This will keep the spike less visable. Don't depend on the cast on tieplate/spike detail to hold the rail without a slight kink when you've cut a gap on a curve. The spike on the outside of each rails curve will ensure the rails maintain a nice flowing curve. If you don't have spikes and want to get to work without waiting to get them, insert a length of brass wire into an appropriate sized hole placed right up against the outside of each rail end. Solder to the rail base and snip off the excess on top.
 
The coeffiecient of thermal expansion for nickel silver is about 15ppm/degC - which means SOLID (no gaps) piece of nicel silver that is 8 ft long at 32F would expand by 0.072 in at 122F. Figure it out, guys, it's not the temperature, it's the humidity.
 
billk said:
The coeffiecient of thermal expansion for nickel silver is about 15ppm/degC - which means SOLID (no gaps) piece of nicel silver that is 8 ft long at 32F would expand by 0.072 in at 122F. Figure it out, guys, it's not the temperature, it's the humidity.
Click to expand...

And it is not the track, it is the wood.

Modules we build for the modular club have styrofoam top decks, with a (usually) cabinet grade 3/4 inch plywood sides. Our standards highly recommended that you seal all wood parts with paint inside and out, top and bottom.

The track must go on some sort of subroadbed - most use cork - that is attached to the 2" foam top. We have almost no problems with the modules changing size, and no issues with track moving. Where there are problems is with older modules built with dimensional pine, and that aren't sealed properly. And even then, it is the ends or sides warping, not the track moving in relation to the foam.

Hope that helps.

Andrew
 
I can back Andrew, flextrack on foam or flextrack on cork on foam is very temperature/humidity stable, at least in lengths not exceeding 10 ft. (I havn't tried longer yet). I've got both stored in an Indiana garage ranging from a very dry -somethingterrible degrees F up to 90somethingterrible % humidity at +90something terrible degrees F.

Saturday it was 95 deg F, sunny, and raining. The street by my house was steaming.

Did I ever tell you guys we have terrible weather here? :D :D :D
 
Thanks guys, so far.

The baseboard I'll be using is "chipboard" (pine chips compressed into a board) each section 2.4 metre * 1.2 metres. (4 of them). with cork roadbed.

Not sure what you guys call "chipboard", but it's pretty "humid resistant".

The local Model Railway Club (I visited once.... too far away) were using a sort of "bubblewrap" as a roadbed. They reckoned it was quite good to use, and excellent for sound suppression. The stuff wasn't EXACTLY bubblewrap but a similar sort of packaging stuff. (bit thinner, and surfaced on both sides).

Any comments on using that sorta stuff for a roadbed? Previous layout, I found cork very noisy.
 
Hey Woodie,
I've heard of guys using engineered flooring (like Pergo) underlayment foam sheeting for roadbase. It is pretty thin and supposedly has great sound-deadening ability. I myself went with the tried and true cork.
Doc
 
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