Large Scale Central

Why stainless steel is better for DCC

Electronics DCC
#1

Surprise, not talking about track cleaning.

Talking about skin effect and resistance.

So, I think many people have heard about the “skin effect” where AC signals tend to travel on the outer surface of a conductor.

This effect basically reduces the amount of metal that is moving electrons for you. (the skin depth is defined where the current falls to 37% of the outside… )

So you want this “skin” to be as thick as possible so you get the most current, or least resistance (meaning voltage drop around your layout).

I always thought that using SS was a compromise, since it is a lot less conductive than copper or aluminum.

But funny that I did not notice any issues that showed a significant drop.

While I was fooling around recently I looked at the formula for the skin depth, and noticed something significant I had missed all these years. The skin depth (the part of the metal conductor “working for me”) is LESS on better conductors. When I thought about it, I realized this made sense from the more “mobile” electrons in a better conductor.

So the bottom line on DCC on rail, the worse the conductor, the lower the resistance in many cases because of the skin effect, i.e. my SS rail is most likely passing more current to my locos than if I had used brass.

(of course skin effect is only on AC, not DC, but realize that your PWM on your DC trains will will also have a skin effect too).

So, stainless steel track owners rejoice! You no longer have to cower in shame over your poor conductivity!

Greg

#2

I never coward in shame and I am 120% happy I went with Stainless and sold off all my brass before I built my first layout.

The only time I have to clean my track is after ballasting, I can run a train at any moment without the fear of oxidized dead spots.

All my track inside in my yards is brass.

My 2 cents.

Nico

#3

If it was not clear, I’m 100% Aristo SS. I clean my track with a garden hose, and sometimes a swiffer.

I hear it’s harder to get nowadays, but the choice I made has paid off in an unexpected way.

Greg

#4

Speaking of which, does anyone have a source for cd332 SS rail 6ft or longer?

#5

H&R trains has stainless

http://www.hrtrains.com/Scale-G-Large-Scale/433-G-Flex-Track-PK-120-W/Joiner-or-Clamp.html?keyword=stainless

Some Aristo/Polks stainless is still available if you look hard enough.

#6

David Maynard said:

H&R trains has stainless

http://www.hrtrains.com/Scale-G-Large-Scale/433-G-Flex-Track-PK-120-W/Joiner-or-Clamp.html?keyword=stainless

Some Aristo/Polks stainless is still available if you look hard enough.

10’ long! What’s the shipping from Fla?

Did you notice; only $577 for their single rail bender?

#7

They were the first stainless I purchased, and it was way too expensive in the late 1990’s… only the advent of the Aristo track made it affordable.

Yep, the same bender they sold almost 20 years ago, with the price rising every year it seems.

Really nice rail, you can see the differences in manufacturing, but way too expensive for me.

Here’s my 10’ diameter loop of H&R Stainless:

Greg

#8

Thanks Greg. As you know, I run DCC through the rail as well, and have appreciated your advice and conversation for over a decade now.

This “skin transmission” issue is very interesting; and in that context, I’d like to bring up the benefits of NiPl rail from TrainLi, which you already know all about. Its nickle coating is TOUGH, really penetrating into the brass core. This nickel “skin” has perhaps a similar conductive effect as SS; and its core gives the conductivity of brass. You can solder to it (if you really have to, but I prefer SS clamps as terminals). Like SS, it has no oxidation and therefore requires infrequent and mild cleaning. It’s cheaper than SS, and is readily available. TrainLi’s switch offerings are impressive; and I’m quite happy with the product line.

Your buddy in MD,

Cliff

#9

When Polk’s came out with track, I bought a few wide radius ss switches, just in case I ever do either expansion plan (unlikely). I also bought some used Aristo 10 foot stainless at auction last year. Many of the tie strips are actually AMS ties, but they blend in with the Aristo ties pretty well. And, somewhere in the deep recesses of my barn, I should still have a box of 5 foot straight Aristo stainless. I stocked up when funds would permit, so that if I ever do either expansion plan, I would not be stuck waiting for track, like I was with the original build of the railroad.

Yea, I can’t see spending that kind of cash for a single rail bender. I have the TrainLi duo railbender, and it is a cinch to use, and does a great job.

It would be nice if someone would bring back the Aristo line of track again.

#10

Rocky Canyonero said:

Speaking of which, does anyone have a source for cd332 SS rail 6ft or longer?

SS rail comes up quite often on Ebay. Usually from Trainz. There is some 8’ stuff right now.

https://www.ebay.com/itm/332662792790?ul_noapp=true

Tom

#11

Interesting. In the RF world, stainless steel is “no way no how” for antennas, But they have different kinds of needs than conducting.

I’d be curious in a “amount of power conducted over similar size wire” comparisons between copper, brass, and SS. I wonder if there’s some out there?

#12

There might be answers with these results from a search - power conducted over similar size wire comparisons between copper, brass

#13

Stainless in RF becomes a big resistor… You want the best conducting stuff, and you normally don’t worry too much about skin effect per se, since the standard is usually copper over steel, and some protective nickel or something… all the rf is in the copper plating, the skin is very thin in RF frequencies, so the steel core adds/removes virtually nothing.

In DCC, it would actually behoove you to use stranded wire for lowest power loss, but stranded is hardest to keep water out of, and water in the jacket will cause corrosion and can eat through fine wire quickly. So the fine strands of typical landscape wire are great if you never get corrosion in joints, otherwise using coarser stranded wire.

Now, if you don’t have long distances, or can tolerate a couple volts drop on the rails, all this worry is over nothing. If you push the envelope, then go stranded.

Greg

#14

Bob, I remember there being one for DC conductivity, but I don’t remember seeing one for DCC conductivity. IIRC, the actual difference between brass and stainless track was not as much as people make it out to be.

Well you figure an antenna deals with VHF or UHF frequencies, but DCC is down around 100 CPS. So yea, different needs, or needs different properties.

#15

look up “skin effect calculator” and get one that lets you put the DCC frequency in, what is it something like 7 to 9 KHz… actually in the audio band…

The interesting thing is the depth of the skin effect is driven by not only the frequency, but the resistance of the material, and basically you have more conducting area and lower resistance on a solid rod if the metal is less conductive, so a solid rod of SS will actually have lower resistance than brass if there is skin effect involved to a fair degree…

What surprised me was how low in frequency the skin effect was a factor. So a hollow thin wall tube of copper will conduct better than stainless at RF, but a solid rod rod of SS is actually less resistance at lower (DCC) frequencies.

You have to take the formulas or calculators and calculate the resistance with different metals to convince yourself.

Greg

#16

7 to 9 kilocycles, I didn’t know it was that high. I wonder where I got the idea it was 100 cycles from. Now I understand some why DCC has some interesting quirks.

#17

Perhaps you were thinking of the data rate. Things are transmitted multiple times and with a fair amount of error checking. It was designed long ago when electronics was not quite as sophisticated.

Nowadays, that “extra” just gives us more reliability with modern electronics decoding the signal, memory to keep going during interruptions, etc.

Greg