Ok I had some time to kill here today, so I decided to get all sciencey ( I think thats a word) I took a 6ft piece of AML code 332 brass flex track and put it out on the lawn in direct sun at a nice 108 degree day. Measured it at exactly 72 inches inside the house before going outside. after 1.5 hrs out on the lawn it measured 72 1/16 . Thinking the lawn might cool it a bit I stood it up against the house in direct sun, for an additional 20 minutes and it was still 72 1/16. so I am hoping if I leave similar gaps and using some Split Jaw and some joiners I SHOULD be able to keep sun kinks to a minimum. I am planning on floating the whole track on a crushed granite base. So it is supposed to be 116 on monday andd I will re create to see if there is much difference. I will also try to remember to bring my therometer home to get accurate temps on the pieces. Any ideas of if my line of thinking is right?
Pete, the force of expansion and contraction is stronger than rail clamps.
Be careful to not overtighten the SJ clamps, you can bend the screw heads (ask me how I know).
Curves will move a bit, but sun kinks in long straight stretches pretty much cannot be avoided in Arizona. Consider some of the expanding rail sections from SJ if you get kinks.
Greg
My experience is that there will always be expansion and contraction with the direct sunlight and the cold of winter… Was 98 degrees here on Sat & Sun, during the Ops… Sat, the track on my 28 ft bridge (which has an expansion track piece in it) looked like a snake (according to Ric)… The expansion track was fully closed up and created the snake effect with the remaining track, trying to expand… It was also Humid all weekend, so the heat indexes were at 100 or over…
Because of the heat and expansion, my rail joints with the Splitjaw clamps would separate during the winter… What I have done is, every place where the rails separate from the rail joiners, I cut out a small section of track, and install an expansion joint track piece…
Thanks Greg I was kinda hoping you would see this as you seem to have some real world experience on almost all aspects, and give your unvarnished thoughts. I know I am going to make lots of mistakes( its the way I do things) but by asking a lot I hope to make little ones , not the whoppers that wind up killing the desire to have a complete railroad.
Thanks Andy, i understand what an expansion track piece if for, but is it made from a different material or are you just ading small pieces of brass ( in my case) track
So a long time ago, we worked with a friend named Phil in Phoenix. He would measure the air temp, and more importantly the rail temp. He had long straights in his back yard, and the only thing that finally stopped the sun kinks were the SJ expansion tracks. He experimented with different gaps, joiners, etc… SJ came out on top in all tests. I have stainless, which expands less.
It comes in 3/8, 5/8, and 1"… on long runs, about 50 feet or so, our friend needed about 1/2 inch. I realize this is more than the theoretical expansion of the rail, but there is movement in the joiners and also curves move around a bit. I would not order the 3/8" in any case.
It could be worse, you could have aluminum, ha ha!
Regards, Greg
OK cool, thanks again Greg, I am guessing that it will be a process of laying the track then seeing where the problem spots are and adding those in where needed. Yeah Aluminum would be all over the yard, I was thinking about it, but got a deal and went with brass.
From my experience, if you are going to use the SJ expander rail track, then get the largest version… Better to have extra room, than to have to buy multiple smaller ones…
OK Pete, here is a post I made several years ago on another large scale forum regarding expansion of track. Rather than sifting through the rest of the thread to get to the meat, here it is:
OK folks, here are the facts:
Here are a few coefficients of expansion for the various materials used in large scale model track (rail). Coefficients of expansion are expressed in terms of unit of expansion per unit of length per degree of temperature rise.
Aluminum expands at an average rate of .0000123.
Brass is an average of .0000104.
Stainless steel averages about .0000096.
Nickel silver is about .0000093.
These numbers are averages, as there are numerous alloys that make up the generic material group we refer to. I beleive that most aluminum rail is alloy 6061, which is a good grade to use if you are looking for a tough high temper aluminum. The specific coefficient for 6061 is .000013. An example for the calculation would be as follows:
Total temperature rise is 80 degrees.
The rail length is 240 inches (20 ft).
The material is aluminum.
The coefficient of expansion for the aluminum is .000013, the temperature rise is 80 degrees and the length is 240 inches. The total expansion of the rail between the lowest temperature and the highest temperature is .2496 inches ~ 1/4". This is fairly reasonable on the surface, but consider this - I live in the panhandle of Florida. Yearly temperature can vary from in the teens to over 100 degrees. Add the solar heating to that and actual rail temperatures can approach 160-170 degrees. Lets look at the total variation using these worst case scenerios. 240 x (170-15) x .000013 = .4836 or nearly 1/2 inch. I will tell you from personal and career experience, expansion will not be denied (contained). IT WILL GO SOMEWHERE.
Nathan, I am not sure where you got your information, but stainless steel and nickel silver are almost identical in expansion characteristics. Nickel silver (also known as German Silver), is easier to cut and form, solders well with standard soldering tools, and the oxides ARE conductive. Stainless steel on the other hand is very hard to cut and fabricate, does NOT work well with standard soldering equipment, not to mention special fluxes are required to get good bonding, and lastly is the worst conductor of electricity.
The only draw back I see to Nickel silver is the cost and lower availability in the larger scale range. The only place I am aware of that lists the larger rail was Old Pullman, and I believe they have gone out of business, although their web site is still available. If you would like I can post the backup information on the conductivity and expansion on my web site if you would like to view it.
Bob C.
Depending on your track laying method, expansion may or may not be a governing issue. If you float your track on ballast as the prototype (and many large scale hobbyists), the expansion will slide the track some, the curves will get somewhat larger, and for the most part will be inconsequential. If you are going to attach your track to any form of hard sub roadbed expansion will be much more difficult to deal with. Your preliminary experiments are a good indicator of your needs. A method I will someday do the empirical testing on will be to assemble two sections of track using rigid rail clamps. Then remove the small screws from all the tie strips except one section next to on either side of the rigid clamps, allowing the rails to slide in the tie strips - using the as a guide. Based on the math above (adjusting for the ambient temperature at the time the track is installed), gap the sections using standard rail joiners at the gaped locations. It is my intent to use wire loops soldered at the sliding joints to effect electrical continuity.
I hope this helps, and if you have any additional questions I will be happy to see what can do.
Bob C.
the curves will get somewhat larger, and for the most part will be inconsequential.
Since my railroad is almost all curves, and stainless steel track, I do not have many issues with thermal expansion and contraction. I do believe that thermal expansion and contraction does affect the areas where my track wasn’t properly curved, in that on hot days I sometimes have an area where the gauge is off. That’s partly do to my poor rail-bending skills when I first laid the track, and changes due to temperature.
1/4 inch doesn’t sound like much, but when the rail grows by that amount, it can really knock straight track out of alignment.
Believe it or not, we have the same issues on our HO modules. When its cold, the track is straight on the bridge on one module, but when its hot, that track is a gentle S curve. I have also seen where we put in the joiner rails when the building is cold, because the loading doors are open, and its cold outside. Then, the next day, when the building is warm, them joiner rails have lost their gaps, and some are even wedged in quite tight.
So changes in rail length due to changes in temperature does have to be considered when laying track. But since most of us float the track, it can shift as needed with few issues, most of the time.
Pete,
temperatures here are between 30 and 110°F in the shade. but the track was not in the shade…
when i had my outdoors layout, i experienced a maximum difference in length of about 2 mm per foot for 332 LGB brassrail.
as i used the standard joiners (fishplates), i had to push the curves back to the inside, when temperature went down. when it got colder, gaps evolved. but, when it got warmer again, the rails were not nicely pushed together by expansion again. instead they were pushed outside, gaps and all.
Korm, yes, and that begs the question of why do some people put gaps at the joints. Inside where the track is secured to some degree, it makes sense. But outside? I don’t gap the rails at my joiners/clamps, I just let he whole shebang move together.
Pete,
Yes temperature can play havoc on track in Phoenix. However if you float the track in ballast and not attach it down it will not adversely affect the track. I have many long straight sections on my layout. What I have done is put in a few s-curves, not close s-curves but spaced with at least a 2 foot straight section in between. This allows for expansion and contraction. I have seen some layouts here in Arizona where the straight sections look like spaghetti during the very hot summer months. However with the s-curves they stay relatively straight. I also use split jaw clamps.
On our club module we use the expansion tracks because all of the track is attached directly to the frame. In my opinion they work very well.
I am using the Split Jaw Expansion section in two long sections of my floating track that are exposed to the sun all day and I haven’t had a problem. I highly recommend them.
Thanks to all who answered ALL opinions are taken into consideration and the help is always appreciated. Since I was pretty much already planning most track to have long gentle curves ( no real long tangents), and will be floating on ballast, I am thinking that for the most part IF I get any movement one or 2 expansion joints would probably take care of any issues if they crop up. Now I will most likely be waiting until fall before starting to move any ground for roadbeds. supposed to be 116 on Monday! The joy of living in the southwest!
David Maynard said:
Korm, yes, and that begs the question of why do some people put gaps at the joints. Inside where the track is secured to some degree, it makes sense. But outside? I don’t gap the rails at my joiners/clamps, I just let he whole shebang move together.
Some of us secure our track outside. Thus, I have gaps…
Bruce, ok, that makes sense.
i’m not sure it makes sense, but it is the way I have done it. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-foot-in-mouth.gif)
Late to this party. In the Northeast where 100+ is only a few days per year I have all stainless outside and more than half of it is shaded most of the day, so I don’t generally have too much problem. I have a long straight that leads to a big sweeping curve that gets lots of afternoon sun. The straight is attached to wood roadbed in a few places and does bend a bit, but not enough to cause a problem. The curve is attached to ladder roadbed and so far no issues at all. I guess I’m lucky.
I do have some issues with winter contraction. Some of my SJ joints will open up to about a 3/16" gap.
I am about to start laying Aluminum on raised roadbed in the sunny part of the yard. i did not even think about the expansion/contraction issues with Al track before I bought it. Now I’m thinking about designing a “U” shaped tie clamp that will allow movement but still allow me to attach the track to the roadbed.
According to references, stainless steel expands and contracts less then brass. Stainless is generally easier to clean too. So even though its not as good an electrical conductor as brass, I am happy that I went with stainless.
John, much of my railroad is in partial or full shade too. So my track doesn’t get the solar heating as much as it could, just heating from the air. From some accounts I have read from others, that also makes a difference in how much the track expands, a big difference.