Track expansion

[kstrong]

Cool! Sounds like one of those little quirky things. Gotta love things like that. Now all we have to do is figure out how to maintain such a temperature for 2 hours. Cleaning cycle on an oven?

Later,

K

[RhB_HJ]

Hi Kevin,

That's something used in the jewelry trade.

What happens at 440º C held for approx. 2hours the homogeneous mix of the crystalline structure is being transformed into a heterogeneous mix. This will result in the hardening, but as mentioned it depends on the composition of the brass.

BTW no argument, just learning something new everyday. [;)][;)][:)]
In my "former life" I was involved in the "what to do with metals" business and hardly a day went by without me saying "Now that is interesting, who would have thought....."

[kstrong]

QUOTE: Brass can be hardened by heating it to 440ºC, then letting it cool.

That's a new one on me. I hate to sound arguementative, but where did you come across that? Every metalworking reference I've come upon with regard to brass states that it's "not heat-treatable for the purposes of hardness development." (or something akin thereto.) I've seen a few references that show temperatures around 440°C used for annealing (softening) of the brass to counter the effects of work hardening; most common in cartridge reloading circles.

I don't mean to sound like I'm saying "you're wrong," instead I'm quite curious about this. Much like the recent experimentation done on heating brass and other metals in the microwave for casting, this sounds completely contradictory to common knowledge, but I'm sure there's a basis for it. I'd love to learn more about it.

Later,

K

[RhB_HJ]

QUOTE: Originally posted by kstrong

HJ, brass can be "work-hardened" by bending the metal, but heating and cooling it will not significantly harden it beyond the work-hardening that happens by the metal expanding and contracting during the heating process. (And there would have to be a lot of cycles for that to have any significant effect.) Annealing the brass (heating it to cherry red) will make it softer, not harder. It makes no difference how the cooling is done, whether by air or by dousing in cold water. The metal will be just as soft either way. It will harden again as you bend the metal to shape, requiring additional heatings.

Steel, on the other hand, can be brought to different hardnesses by various quenching processes, from what I've been told. I've not worked with steel in terms of wanting to change its hardness.

Later,

K

Kevin,

Brass can be hardened by heating it to 440ºC, then letting it cool. Admittedly the degree of hardness will vary with different brass alloys - the same as happens with work-hardening, be it bending or drawing.
OTOH if you heat brass to cherry red and douse it in cold water in will be as soft as butter.

Accurately hardening steel i.e. a semi-finished part that need to keep its shape and dimensions so that it is within +/- 1 Rockwell C is akin to science. Many were called but only a few chosen.[;)][:)]

[kstrong]

The suggestion to lay track when it's hot out keeps getting thrown around--and in theory, it's a great idea. Only one little problem. You're handling HOT rails! Not "warm to the touch" or "mildly uncomfortable," but "leave marks on your skin and send you inside for the aloe" hot! (Ask me how I know...) Gloves are a necessity, and present their own brand of uncomfortable in 90° heat.

If you're going to be mounting your track to any kind of quasi-solid base, just gap the rails at every joint. I left a 1/8" gap at various joints along the line to compensate for expansion.

One caveat with this method, though. Over time, dirt will undoubtedly accumulate inside the rail joiner. Dirt doesn't compress very easily, so over the course of a few years, your expansion gaps realy won't perform their intended duties, as the rail will want to expand into the space occupied by the dirt. You'll want to periodically go through on a cool morning with some compressed air and blow the dirt out of the joints. You don't have to do this terribly often, but if you make it part of your spring maintenance routine, you'll be in good shape for the remainder of the summer and fall.

If you're just floating your track in the ballast, expansion really isn't much of an issue. The track will move one way or the other as it expands and contracts. The downside to this is that it will also work its way up and out in the process, meaning you'll have go through and relevel the track fairly regularly. On my old line in Rochester, I found myself "adjusting" the track every few months or so during the summer. Not a huge problem, just one more step in the maintenance routine.

HJ, brass can be "work-hardened" by bending the metal, but heating and cooling it will not significantly harden it beyond the work-hardening that happens by the metal expanding and contracting during the heating process. (And there would have to be a lot of cycles for that to have any significant effect.) Annealing the brass (heating it to cherry red) will make it softer, not harder. It makes no difference how the cooling is done, whether by air or by dousing in cold water. The metal will be just as soft either way. It will harden again as you bend the metal to shape, requiring additional heatings.

Steel, on the other hand, can be brought to different hardnesses by various quenching processes, from what I've been told. I've not worked with steel in terms of wanting to change its hardness.

Later,

K

[RhB_HJ]

QUOTE: Originally posted by cacole

I remember reading something several years ago from a metallurgist who explained that most model track is extruded and has a lot of internal stress.

His suggestion was to connect a power pack to a section of flex track (in HO or N scale), and turn up the throttle until the rail got hot. This would supposedly allow the atoms to rearrange themselves and relieve the stress in the metal, so it wouldn't expand as much after being put onto the layout.

Whether this is true of G scale track, I have no idea.

Interestingly enough if you heat up brass und then let it air-cool it will get harder. To anneal it it needs to be shocked in cold water.
Of course this only applies if you want to anneal brass using a torch!

[cacole]

I remember reading something several years ago from a metallurgist who explained that most model track is extruded and has a lot of internal stress.

His suggestion was to connect a power pack to a section of flex track (in HO or N scale), and turn up the throttle until the rail got hot. This would supposedly allow the atoms to rearrange themselves and relieve the stress in the metal, so it wouldn't expand as much after being put onto the layout.

Whether this is true of G scale track, I have no idea.

[RhB_HJ]

QUOTE: Originally posted by ondrek

QUOTE: Originally posted by RhB_HJ

If possible lay your track when it is really hot. You sweat it at the time, but don't later!

Or you could pre-heat your sections in the oven set at 100.

make the wife made but oh well

Kevin

Why not[:o)][;)] , let me know how you fit the 5 and 10 ft pieces.[8)][8)]

Now all kidding aside, when I handlaid track in the smaller scales I made sure it was plenty warm in the room (28 - 30ºC). Chances are it won't get hotter than that indoors - not if you pay for the heat.
If one applies the same method outside, you're smiling - errrrr I mean sweating first and smiling when operating later.

[ondrek]

QUOTE: Originally posted by RhB_HJ

If possible lay your track when it is really hot. You sweat it at the time, but don't later!

Or you could pre-heat your sections in the oven set at 100.

make the wife made but oh well

Kevin

[RhB_HJ]

If possible lay your track when it is really hot. You sweat it at the time, but don't later!

[ibikeil]

I also live in Northern Indiana and have had my track down since May. So far even the 100 degree plus days we had this summer haven't caused any problems for my Aristo brass track. My track floats in chicken grit ballast with split jaw clamps holding everything together.

We'll see what the winter brings!!

IBIKEIL

[markperr]

Your temperature extremes in Northern Indiana aren't enough to worry about track expansion, at least for brass track. I live in southeast Michigan, so we are virtually at the same northern lattitude. I have never had a problem with track expansion.

Where I've heard the most complaints about track expansion is from guys in the southwest where the temperature extremes get into the 110's.

Mark

[Greg Elmassian]

Just to add a comment, leave expansion gaps when laying track, one tip I received was to put a credit card between the rails at installation time.

Also, try to break up long straightaways with curves, they can help avoid kinks in long stretches. Curves also add visual interest.

Regards, Greg

[Anonymous]

Gentlemen,
Thanks for your response. I guess I should just start laying track.
Thanks again,
Jim

[Capt Bob Johnson]

I think the man has said about what needed to be said, I can only echo the same for Slower Lower Delaware!

[cacole]

The key factor is that you need to leave the track loose (not fastened down) so it can expand and contract with changes in the weather.

Even here in Arizona, I don't have any problems with track expansion and contraction because it is free to float. I use AristoCraft brass and stainless steel track, and just rely on the setscrews that come with it to hold it together.

I don't use track power at all, so electrical connections are of no concern.

Another layout here has a straight run that is elevated along a 100-foot wall, and is track powered; and they have had no problems that I know of with expansion and contraction.

Wintertime temperatures here dip into the upper 20's because we are at a high altitude (5,500 feet), and summertime temperatures sometimes exceed 100.

[Anonymous]

I'm planning to build a garden railway soon and I'm curious about track expansion. I live in Northern Indiana and temperatures range from sub zero to the high nineties. I know I can calculate expansion for brass and stainless steel, but does anyone have any idea about numbers for nickel silver?