Track expansion ?

[Anonymous]

I'm just beginning the planning for an 'N' layout. I have a couple of options. The first is in a controlled and constant environment (a normal room in the living area of the house)but would have to be roughly half the size of the second option which would be in an insulated attic. This attic bonus room has AC/heat on a seperate unit from the house but it is usually turned to 'comfort' ranges only when someone is in there. I would rather not have to maintain the AC/heat at 'comfort' ranges year round as it would get pretty expensive for the 8 hours per month I might spend there....

So my question is. Can I do a compromise and keep the temp within a certain range without having track expansion/contraction problems? If so how much temp variation could there be? Any thoughts would be appreciated...

[selector]

It would be more likely the ambient humidity, and the wide swings thereof, that would give you problems with your track. I cannot say for certain (not an engineer), but my guess is that you'd have to have 10' soldered sections of rail experiencing temperature swings in excess of 30 deg Celsius to get deflection caused by 1/16" gaps closing at each end. But humidity, if using wood anywhere on the layout, will expand noticeably with an increase in humidity by 30%. That will put severe strain on glues, nails, joiners, solders, etc.

[Anonymous]

Thanks for the response. I had just assumed I would have more problems with the heat since there was such a potential for temp swings....

I live in an area that has a variation of about 30% in humidity over the course of a year. I suppose I might need to look into a dehumidifier and try to offset the variation that way. Anyone have any experience doing this?

QUOTE: Originally posted by selector

It would be more likely the ambient humidity, and the wide swings thereof, that would give you problems with your track. I cannot say for certain (not an engineer), but my guess is that you'd have to have 10' soldered sections of rail experiencing temperature swings in excess of 30 deg Celsius to get deflection caused by 1/16" gaps closing at each end. But humidity, if using wood anywhere on the layout, will expand noticeably with an increase in humidity by 30%. That will put severe strain on glues, nails, joiners, solders, etc.

[cacole]

Expansion and contraction of the wood that your benchwork is made of is more of a problem than the track.

When I first joined our local HO scale club, the layout had been built on 1/4 inch thick plywood and one layer of Homosote using the cookie cutter and L-girder method. The club is in a non-air-conditioned building with no heat. Warpage was horrible and derailments were frequent. We finally decided to tear the whole thing out, throw it in the trash, and start over.

Our new benchwork is a 2x4 framework supporting hollow-core doors, covered with two one-half inch thick layers of Sound Board (Upson Board). Before any track was laid, an experiment was conducted to determine the amount of expansion of nickel-silver rail because we were going to have straight sections of almost 40 feet in length along one wall.

Two pieces of Atlas HO scale flex track were used. Measurements were taken of all 4 rails while the track was indoors at normal room temperature. It was then put outdoors on a July afternoon in full sunlight for three hours when the air temperature was hovering near 100 degrees. The length of all 4 rails was again measured and recorded, and the temperature of the actual rail was measured as nearly 130 degrees. The track was put into a chest-type freezer overnight and the rails were measured at 0 degrees. Between 0 and 130 degrees, a 3-foot long piece of flex track rail contracted less than 1/64th of an inch. Based on these results, we decided that no extra expansion joints would be necessary. We have had no warpage on the new layout, which is now six years old.

[dgwinup]

If you have a regular time when you will be modeling, add a setback thermostat to your HVAC unit. Get one that allows you to set every day separately. Set it for your modeling time period. When you are not modeling, the thermostat will maintain a temperature that won't bust your budget.

In the winter, it shouldn't take long to bring your train room up to a comfortable temperature. In the summer months, cooling will take longer.

Darrell, quiet...for now

[selector]

QUOTE: Originally posted by Sackbut

Thanks for the response. I had just assumed I would have more problems with the heat since there was such a potential for temp swings....

I live in an area that has a variation of about 30% in humidity over the course of a year. I suppose I might need to look into a dehumidifier and try to offset the variation that way. Anyone have any experience doing this?

One morning, about two weeks into the non-heating season on Vancouver Island (where it rains almost non-stop from November to March) last year, I was also two weeks into a completed trackplan. I had been heating the house, but mostly the basement where the layout is, with a substantial wood stove. Needless to say, moisture was not a problem during its construction, and during the first week or so later.

On this fateful morning, I happened to glance along the diagonal main that crosses my larger bridge. To my surprise, the flextrack, which I had not fixed to the deck, had deflected to one side in a substantial wow. And "wow" is what I exclaimed. I knew instantly what the problem was, and did nothing more than go to Home Depot and purchase a dehumidifier. Within six hours, the flextrack had returned nearly to a neutral position.

So, I have both the experience....and the dehumidifier. [:D]

-Crandell

[j1love]

I am by no means an expert, but there was an article in MR about metal framework for support of a layout. I believe that they used "L" and "I" shaped metal beams for support; and fastoned the risers, deck and sub-roadbed to the metal frame. My thoght was in building your layout, most of the deflection comes from either the sub-roadbed, but ultimately the frame.....so you may want to consider the metal frame for a rigid and non warpable foundation to your layout. Just my [2c] [swg]

[ericboone]

Masonite spline or extruded foam construction would both greatly reduce if not eliminate temperature and humidity problems.

[tstage]

Hey, Sackbut!

Are you perchance a trombone player? Just curious...

Tom

[fwright]

It is not the humidity itself, but the changes in the humidity that will cause the wood (including plywood, but to a much lesser extent) to expand/contract. There are several cures:

- control the humidity of the room. Highest on-going costs, but most effective. Also increases comfort for you.

- massive lumber construction (overkill). Reduces the rate of wood expansion /contraction due to fact it takes time to change moisture content of bigger wood pieces. High upfront cost, can still have problems long term.

- paint/seal all surfaces of benchwork. Again, works by significantly slowing change of moisture content in wood. Seems to resolve the problem for most MRs who have tried it. It is a hassle, because painting just some surfaces leaves you open for problems with the unpainted pieces. Can also enhance the appearance of your benchwork. Since the heating and cooling will help control the humidity, even if sporadically, this will probably be a good enough measure for your situation. Let your lumber sit in the attic, weighted and fixed to prevent warping for a few weeks before construction so that there is little change in humidity during the actual construction.

- Substitute plywood strips for dimensional lumber. Plywood is more stable, so this helps. Similarly, L girders and the like are more stable than single pieces of lumber.

- use composite benchwork such as wood glued to foam, or wood screwed to metal. Foam/metal will help stabilize the wood. There will be stress on joint where wood is mounted to other materials when moisture content changes, but this joint stress actually increases rigidity of benchwork.

Of course, you can use multiple approaches to the problem as well.

my thoughts, your choices
Fred W

[Anonymous]

Tom,

Yepper.....old 'boner' from way back...not many people catch that....you must be a musician yourself..[:D]

QUOTE: Originally posted by tstage

Hey, Sackbut!

Are you perchance a trombone player? Just curious...

Tom

[tstage]

Yep. Trombonist by training and played bass sackbut for 13 years. (Love that era of music.) Knew you had to be or know what the term meant. No one would wear that moniker arbitrarily.

Tom

[Anonymous]

College music major and played 4 years for the Air Force Band...but not currently under baton...LOL

Get to play on occassion but not anything close to regular....On the road a lot so it's tough to find a 'gig' with that odd schedule....

Infamous majoretted quote........"Be afraid of the trombone section.....be VERY afraid!"

QUOTE: Originally posted by tstage

Yep. Trombonist by training and played bass sackbut for 13 years. (Love that era of music.) Knew you had to be or know what the term meant. No one would wear that moniker arbitrarily.

Tom

[colvinbackshop]

Heat and humidity changes will move the earth (our MRR world's earth) big time. Here in Northern MN. I heat and humidify in the winter and de-humidify in the summer....Still there are changes!
One thing that I've adopted to minimize the track "WOWing" is to NOT solder every rail joiner. I now only solder the ones that are also the feeders, or around corners. Seems to have helped, as I haven't any problems with track doing an "S" when supposed to be straight, since giving some expansion room.