Gapping track for expansion

[Wrangler]

How wide should the gap be(.000)?And how far apart should the gaps be?Also is the correct spacing for feeders every 6 feet?I have the roadbed down and used latex caulk and will use caulk to adhere the track to the roadbed.

Thanks for the help,

Vince

[BigG]

   Hi,  I don't have the coefficient of expansion for nickel-silver track, and I work in a relatively stable environment, but I use about the thickness of a computer card or 3 (.0065" each) between flextrack sections of about 3ft. Looking at an insulated railjoiner will show about the max spacing. My road is rather curvey, so some expansion will just disappear in the curves. Long straightaways are something else, and any expansion will have nowhere to go except cause a kink. If you lay track on a warm day, shrinkage is not a problem.    As for feeders, their reason is to ensure that the rail joiners don't have to carry current. As you ballast or claen track, the glues and liquids can cause resistance in the joints, resulting in uneven performance. This is especially true of DCC which doesn't take to sudden voltage changes. I put a feeder to each flextrack section, or for low-use sections, every-other one if they are short.

   Do something that can save you frustration later:  slightly round the ends of your rails. This will give the wheels a chance of accepting small misalignments without stubbing on the next section.

   Hope this helps,     Have fun....   George

[tomikawaTT]

In order to give a definite answer about gapping for expansion a person would have to know the following:

1. What is the expected temperature range in your modeling space?
2. What kind of humidity problems do you have to contend with?
3. What about your benchwork/subgrade/roadbed will effect the track geometry.

As you can well imagine, the situation is very different for:

1. Someone fortunate enough to have a fully climate controlled space where changes in temperature and humidity are measured in small single digits.
2. Someone working in an area where their humidity is low (and reduced further by heating) in winter and extremely high in summer.
3. Someone working in an un-climate-controlled garage in the dessicated desert, where the temperature over a year will range from below freezing to 120+, but who considers two-digit humidity to be high.

I can be somewhat more specific on feeders.  Every rail should be connected through soldered or screw terminal joints to a feed wire.  Ways to do this:

1. Solder a drop to every length of rail, no matter how short (Overkill!)
2. Solder all rail joiners except those deliberately insulated (if there are no expansion/contraction problems.)
3. Solder every other rail joiner and have a drop somewhere in that 6 foot length (what you seem to be leaning toward.)
4. Solder jumpers around all uninsulated rail joiners and have one drop somewhere close to the center of the electrical section - which may be as much as 30 feet long.  (This is my preferred method, but my longest sections are under 15 feet.)
5. Etc, etc, et al, ad nauseum...  There are about as many methods as there are active layout builders.

If whatever method you finally choose results in bulletproof power feed to every locomotive, it's good.

Just my .  Other opinions will differ.

Chuck (modeling Central Japan in September, 1964)

[MisterBeasley]

What did you use for constructing your layout?

In most cases where people have problems with expansion/contraction, it's actually the base material of the layout that's growing and shrinking.  Plywood and the various forms of chip board are much, much worse than nickel-silver.  You will be much more immune to these problems if you use foam, or if you use cookie-cutter construction rather than a flat table.

New Jersey shouldn't bee too bad.  Pity the people in places like Hawaii, with extreme maritime climates.  Yeah, pity the people of Hawaii.

[RR Redneck]

If you are layin track in the summer you dont have to leave gaps, but in winter, I just leave a gap about the size of an index card.

[floridaflyer]

Living in Florida it was necessary for me to put a/c in my garage. that seems to work ok.  I solder curves and have my straights and turnouts free I still used a index card on short straightaways, and a credit card width on long straightaways coming out of a soldered curve.  Six feet is a good distance for feeders. Some like to have every section of the  track have a feeder.  Personal choice comes into play here. Still have to go through a "Winter" on the layout but so far everything seems to be running ok. My a/c keeps the room in the73-80 range, but does control humidity. in the winter there will be no, or very little, heat so the temp will drop into the low 60's some of the time, and the humidity may rise. I may have to add a humidifier, but I'll wait to see how it goes. 

[Wrangler]

Thanks for the replies.The layout is in a heated/air conditioned space.I posted this thread because I don't want to make any mistakes and then have to correct them.

1 Space is climate controlled

2 1/2"plywood with 1" foam

3 code 83 track

4 open benchwork(girders/risers)with a cookie cutter top

All advice is appreciated,

Vince

[selector]

General purpose rule of thumb...use the thickness of your NMRA gauge as a spacer, and it can be every 3' section if you are willing to use feeders on evey section, or every two sections that are soldered...so a gap of that thickness every 6'.  That should take care o' ya.

[pcarrell]

General purpose rule of thumb...use the thickness of your NMRA gauge as a spacer, and it can be every 3' section if you are willing to use feeders on evey section, or every two sections that are soldered...so a gap of that thickness every 6'.  That should take care o' ya.

Thats exactly the way I do it.  I'm in a climate controlled room though, so it may not work so well in a garage, attic, or basement.

[spidge]

I used a cutoff wheel on my N-scale garage layout. All joints are soldered and the gaps are cut in low stress areas of the trackwork, like straights and slight curves. I thought I went a little overboard but its seams every summer a new kink shows up. I would use a smaller gap than the cutoff wheel as in the winter they are noticable. This is my third summer with the current layout and I only had one kink in the entire layout , this time, so I hope that will be the last.

[Vail and Southwestern RR]

I did look up the coefficient of expansion for NS a couple weeks ago, and did a quick calculation.  For a 90 degree F temperature change, the expansion was about a tenth of an inch over ten feet.  That doesn't sound so bad.  But, if both ends of that are fixed, the center would have to move almost 2.5 inches to accomodate it.  The basic guidline of a business card width every 6 feet or so seems pretty sound.

Now, I imagine the other elements of the layout may change more due to changes in temperature and humidity, but the means of attachment to the layout have some degree of flexibility, even the pretty solid ones.  But if the track is soldered together everywhere, it is a single unit, and still needs to be allowed movement.  Of course, less temperature change, less movement.

 

[floridaflyer]

One thing you can do is prime and enamel paint all surfaces of the benchwork. This will help keep moisture out of the plywood. I also have 1/2 " plywood and took this added step to add safety to the benchwork. so far so good