Monitoring Layout Shrinkage or Growth

[narrowminded]

Here's a dumb but I think VERY handy thing I came up with for my layout that might be useful to others.  It was in response to recent posts with seriously damaged track due to buckling, pretty much assumed to be the result of the recent extremely cold therefore extremely dry, weather.  Chris333 and others had some trouble and the horror stories from others were plentiful. I had what I think might have been shrinkage that allowed a styrene road that was very closely fitted to push a rail out of gauge.

I made this video rather than try to explain in text what I did.  Stupid simple but I think VERY handy as it affords no BS information.  I thought it might be useful to some others.  Enjoy!

[Maletrain]

Good idea!

I expect that others will comment about not accounting for changes in the rod lengths due to temperature, or some other issues.  But, the track rails will also change with temperature, too.  So, what this will provide is a real measurement of how the wooden structure changes compared to a straight metal rail.  Results will probably be somewhat dependent on how the temperature and humidity correlate in your region and house's climate control system, as well as what materials and methods you used to make your benchwork.  So, others using the same apparatus might get slightly different results.  But, it will be a good indication of how much rail gap you need per foot to avoid kinking in your layout.  At least, it will after you have sevearl years of data.  Of course, by then, you will already have made the gaps and found (or not found) kinking problems the hard way.  So, this may be  more use to the rest of us than to you, unless you need to rebuild.  To assist us, please tell us how much gap per foot you use on your rails and whether you have any kinking, as well as the changes in your gauge over time and the temperature and humidity for each reading.  Considering how the humidity changes take a while to make the layout expand or contract, the best data would probably be something like routine weekly readings of temp, humidity, gauge reading and maybe even a couple of shim-based readings on particular rail gaps on your layout- maybe 2 facing 90° apart.

[narrowminded]

You've got the point of the effort.

In this area (Pittsburgh) I don't expect to see much change until spring/ summer and then, don't know how much to expect but won't be surprised by real numbers just based on anecdotal evidence from living here.  Doors that work in the summer and not the winter, seasonal floor creaks, etc.  That's kinda' the point.  

If a problem surfaces and with all of the potential contributors, did the board move?  And was it a few thousandths or whole fractions?  At present, I don't know that answer.  When planning gaps, what movement am I trying to accommodate?  It would really suck to very carefully set gaps at .010" only to find out later that they should have been .012".  No difference in execution and effort but results that are bad just for lack of the real story.  And what time of year am I doing this work?  If it's the driest time of year maybe very little gap is needed as it will only grow, not shrink.  And then the reverse situation.  Just having good data, especially when it's at a small effort, will be useful to me during construction and down the road if problems ever arise.  It would be very nice to know the honest answer to this one variable.

[narrowminded]

Let me add that this piece could be even simpler. As simple as a fixed end, single rod, and the other end allowed to float through its fixed, slip fit guiding block.  Then a collar fixed on the rod near the floating end which is where the measurement would be made.  The results would be the same.  What I made in two parts was done for a couple of reasons.  One was the ready access under the board to easily take the measurement and the other reason was ready availability of the rod material.  The idea or its usefulness doesn't change.  Again, hope it helps somebody.

[Maletrain]

Yes, a simple rod, fixed at one end and sliding through a hole drilled into a metal block at the other end would work.  That way, you could just use the depth measuring function of the caliper to read how far out of the block the end of the rod is at each measurement time.  You could arrange to do that from the side of the layout, so access would be very easy.  You would just have to make sure that it was put somewhere that you would not catch something on the end of the rod and bend it.

Since somebody is probably going to bring-up the issue of the metal expansion and contraction with temperature, maybe the "rod" could actually be some stout nickel-silver rail, so that it exactly mimics the expansion and contraction of the rail use on the layout, even though it might be code-[somenthing big].

[peteski]

Since somebody is probably going to bring-up the issue of the metal expansion and contraction with temperature, maybe the "rod" could actually be some stout nickel-silver rail, so that it exactly mimics the expansion and contraction of the rail use on the layout, even though it might be code-[somenthing big].

I think that it is pretty much established at this point that it is not the metal (rail) expansion/contraction that is the problem - problem is the wood in the layout's frame/base that is the main culprit.

[Chris333]

I missed the part where this fixes my layout 

[nscaler711]

I missed the part where this fixes my layout 

Maybe you should use steel studs for your layout construction. 

In all seriousness, the place I work at pretty much requires it for all wall construction, and from what I have seen there is very little expansion and contraction. It would also be very light benchwork, and sturdy when plywood or even drywall is affixed to it.
But that's just my "experience"  here though... When I find a more permanent living situation, I'll most likely go that route as it's really easy to work with...

[narrowminded]

The difference between steel and nickel silver expansion is really very small and would be temperature effected only, not humidity.  If temperature swings are your issue, nickel silver expansion would be slightly greater than steel, like about .0025" over 80" and a fifty degree swing, or the rods could be replaced with brass which would have a slightly greater expansion rate than nickel silver, like .0008" (less than 001") over 80" and a 50 degree temperature swing.

If temperature swing was an issue this could always be corrected by calculation, use brass rods which are very close to nickel silver, or get nickel silver, but whichever way was deemed necessary or useful the method is there to acquire honest and useful dimensions.  For me it's the humidity effected materials that are the unknown and this addresses that.  And as that information is acquired it may help me to make decisions about materials as well as define expansion gaps that are reasonably assured will work.

[alhoop]

I think that it is pretty much established at this point that it is not the metal (rail) expansion/contraction that is the problem - problem is the wood in the layout's frame/base that is the main culprit.

Not to me. For the most part the coefficient of expansion for nickle-silver is twice that of wood.
I never had to cut gaps in my benchwork -- only the NS track.
Al

[Maletrain]

Alhoop's post illustrates the rational behind my post about using nickle-silver rod.  I just think it would save a lot of posts and nit-picking calculations on thermal expansion coefficients and humidity expansion coefficients.  In any real location, the humidity and temperature will both change with time, and not by the same relationship at every location.  So, there is a tendency for people to look at minutia when discussing this subject.  Since what we are really worried about is the difference in the length of benchwork material compared to rail material during the variations, it just seems that making that comparison directly will avoid a lot of red herring conversations/posts.  If a bunch of us do what narrowminded is doing, in different locations with different benchwork, the really important factors will probably become inescapably obvous to all of us.

[peteski]

To me this discussion is pointless. Why not just make sure that the track has enough expansion gaps to prevent any distortion.  Even if we measure the dimensional changes (regardless whether those are of the layout's base or the track), that will not change the fact that if not gapped properly, the track will at some point buckle.  Well, unless the layout resides in a completely temperature- and humidity-controlled room with constant temperature and humidity, and the lumber is allowed to stabilize (season?) for some time in that room before it is used for the layout's construction.  But then we wouldn't need to meaure the dimensional changes.

I'm also surprised that nobody mentioned the dimensional changed of the plastic tie strip of the track. 

[narrowminded]

To me this discussion is pointless. Why not just make sure that the track has enough expansion gaps to prevent any distortion.  Even if we measure the dimensional changes (regardless whether those are of the layout's base or the track), that will not change the fact that if not gapped properly, the track will at some point buckle.  Well, unless the layout resides in a completely temperature- and humidity-controlled room with constant temperature and humidity, and the lumber is allowed to stabilize (season?) for some time in that room before it is used for the layout's construction.  But then we wouldn't need to meaure the dimensional changes.

I'm also surprised that nobody mentioned the dimensional changed of the plastic tie strip of the track. 

... or the foam,  or the plaster, or the plaster cloth over the foam.   Plastics in general expand more than brass or steel with temperature changes.  Fiberglass is similar.  Look at the tie design under ME and Atlas flex track and you'll see differences between them that might matter if the base moves much.  Etc, etc.   Gaps are clearly a good idea.  How MUCH of a gap and how often to be sure it's good?  Well that depends....

Humidity and wood don't play well with each other and that's a potential issue for me and is why I'm getting this information for myself on my specific layout.  It occurred to me that somebody else might find it useful, it's stupid easy, it matters, and I'll always be able to check at least this factor.  I may find I should add a humidifier as this track is already laid and the layout has been moved from its original environment which my memory suggests was a not too dry basement and now it's in an environment that does get dry in the winter and can get pretty humid in the summer.  And rather than wonder if I need or should have a humidifier, or purchase one unnecessarily and then not know if it's set to accomplish the intended purpose, I'll take a measurement and either get to work on a fix or sit down with a coffee and run a train, content that all is good with the world.   And if I ever have a problem (I just did, second one and thinking about it, maybe third, fortunately none catostrophic) I can check this and quickly eliminate it or blame it and with something pretty conclusive, not left wondering if this was it.

[peteski]

I have no problem with your idea for a measuring instrument (even though I still don't see a real need for one, if the track has gaps in it). What I thought was pointless was when the discussion advanced to which metal to use.  We are not splitting hairs here. But then again, this is the Railwire and we often get really deep into the minutia of things.  I guess I'm just as guilty as anybody else here (just on different subjects).

[Maletrain]

What I thought was pointless was when the discussion advanced to which metal to use.  We are not splitting hairs here. But then again, this is the Railwire and we often get really deep into the minutia of things.  I guess I'm just as guilty as anybody else here (just on different subjects).

And that is exactly why I suggested using the actual rail material - so we might avoid all of that minutia.

But, of course, on TRW, the minutia is raised anyway, even if just to show that it is not worth talking about.