This may be a dumb question but it seems pretty basic to me.
The rationale of the 3-rail AC analog system vs 2-rail DC analog was clear to understand.
But now in digital operation even Marklin systems supply DC power to the tracks, or so I am told.
So is the retention of AC locos running on 3-rail tracks which carry DC power really a legacy issue to ensure that the huge installed base of 3-rail track from earlier analog and infant digital days remains usable?
In other words, would Marklin, if starting from scratch and without multi-decades of 3-rail AC production behind it, just go for a 2-rail DC system in the digital age?
Or is there still some basic technical advantage in 3-rail AC operation?

Loop two rail track back around on itself and you have your answer. The three rail system eliminates the polarity issues when doing layouts that are more than simple loops.

What you were told is half false and half right. AC and DC uses both the Pulse-width modulation (PWM). You may say that it is a kind of "rectangular current".

For more detail information have a look here, please:
https://en.wikipedia.org...i/Pulse-width_modulation

You are from Belgium, here it is in French too:
https://fr.wikipedia.org...de_largeur_d%27impulsion

Because plenty of Belgium people do also speak German (yes, the Belgian people are very good in languages) here are a movie tutorial for a digital controlling of a MRR by a computer. Unfortunately these movies (or tubes???) are only in German. These 16 movies are provided by Modellbahnshop-Lippe (MSL).

Modellbahnshop-Lippe tutorial for a digital MRR

Especially "Teil 1 analog Modellbahn" and "Teil 2 Modellbahn digital" shows the main differences.

midwestbls explains in post #4 in short words the practical advantage between the tracks without and with "bumps in the middle of the rail ties".

Another very big difference between two line-tracks (without bumps = DC) and the three line-tracks (with bumps = AC) are the needed isolated axles for DC rolling material versus the not isolated axles for AC rolling material. To alter this on AC and/or DC layouts, indeed it would be a very expensive matter.

That's not correct AFAIK.

Digital control supplies constant power to the track with the power being switched many times a second to provide the "bits" of data (0 and 1) necessary for control (such digital power is neither DC nor AC). The waveform is more square wave than anything else. However try putting a Marklin AC analog loco on track that is powered by a digital controller and see what happens.

OK. DC digital systems do the same thing, send square wave form signals along with power through the track. Why is AC better?
I repeat, I ain't an agent provocateur, I just want to know why.

With digital operation, "DC" just means "two-rail" and "AC" just means "three-rail" - the track current is the same.
No PWM used on the track with digital operation - PWM is sometimes used for analogue DC operation.

Two-rail looks better, three-rail makes reversing loops more easy.
Three-rail has a huge installed base. Conversion from three-rail to two-rail is complicated.


OS/2 was the successor of Windows with a clean, newly designed API. The better system does not always win against an older system with a huge installed base or a huge loyal fan population.


It would be better if real trains would use 50 Hertz instead of 16.6 Hertz AC.
In the ’70s there were plans to introduce automatic couplers in Europe. It never went into wide-spread use.

So we still have obsolete systems in 1:1 and in 1:87 (three-rail).

Hi all,

For me the major advantages with 3 rail is the additional current pick up and return. On 2 rail you only have 2 tracks to provide this. With 3 rail you should in theory have a better system. Even if one wheel is dirty or a pice of track is dirty there is a good chance the current return can find a way home

I don't have much experience with 2 rail but my impression is that it is less forgiven than the old 3 rail system.

And when you are less dependent on the wheels to provide all the current, you can afford making heavier locomotive with more traction tires, than you could with 2 rail locos.

I also like the simplicity of isolating one outer rail for feedback control.

Brgds Lasse

I did used Märklin digital K tracks and now i use two rail DCC.
There is big difference by use the system and in fact does Märklin track system not tell better than two rail.
Märklins tracks(with thin metal and "edelstahl") oxid much worse and faster than two rail made of nickle silver.
I was planning to build up an new Märklin layout,but decides to keep on with two rail.
I have seen Märklin layouts sometimes with bad contact.
Why Märklin keeps on with the three rail is about tradition with the pick up shoe.
Today two rail is even better than for 20 years ago thanks for technology to support better way of the contact.
Even Märklins locomotive do needs help to push the train past over the dirt on the tracks.
I like two rail better for the looking after prototype as possible.
You need more work by use Märklins tracks instead of two rail.
It´s my fact and results after tested and use trains.

Goofy,

Your're right both systems need clean tracks.

It's funny the question has still not been answered..............


All I know is I love Marklin!

Michel

One more thing:

When it comes to maintenance, I found 2 rail to need LESS than Marklin and less of a need to clean tracks.

However, I am comparing digital Marklin to analogue DC.

I have only a tad of experience with DCC, but my Ice 2 train in DCC has not been a great experience - at least with a test run on my MS2 (something inside it shortens the MS2) - it was fine with the Multimaus a year or two ago. It still runs great in standard DC.

Overall, in North America I think if one should only choose ONE system, I would be hard pressed to suggest Marklin to a newcomer with no nostalgic reasons to pick Marklin.

To begin with, I would recommend standard DC in 2 rail to most parents - this way they can have a choice of US, Can and European trains. If then they really like it, then they can choose DCC and the higher costs and headaches DCC entails.

Again, my 2 cents' worth.

Have a good weekend everyone.

I chose Marklin because 1) it's what I grew up with and 2) I've never had any problems that would push me to consider other brands.

IMO 3-rail still exists not because it's "better" (that's debatable) but rather because of those loyal to Marklin. Unless we stop buying and demand a change, why would Marklin switch? And for me, I like manufacturers of both systems but I don't see a reason to switch. Some don't like the center contacts. They don't bother me. It all comes down to what's most important to you in your model railroads.

Stop, stop, stop. I never wrote or suggested this. Also I do not think that your question is a dumb one, as you wrote by yourself. I think it is a good question and while I started my relaunch in MRR I asked myself the same question. And for myself I found an answer. An answer which may not satisfy you. I agree this, but then let us write more about from that point onwards and do not think in any case that I believe you are a provocateur. For me absolutely not.

What you are quoting here was only a direct answer with an explanation to michlvr. Telling him, that Maerklin knows the answer to his question already. It has nothing to do with your question.

"... simply explaining why Maerklin 3-rail AC is best." Again, I never said this, that AC is better than DC. It is a philosophy. Because the electric power does not care, if it is transported by a alternating or direct power tension. Current is just current. AC or DC each of them has advantages and disadvantages.

By the way, this was already a dispute between Edison and Westinghouse, known as the “War of Current”. Please read more about it here: https://en.wikipedia.org/wiki/War_of_Currents.

Perhaps I should have it more explained to you, instead just sending you links, which of course you could not have seen yet all of them. OK, links are easier to handle than to write a full thesis.

I decided to use AC, because it is easier to handle for kids and myself with the polarity of the current. Using AC, I do not have to take care about it, because by the definition of the system I cannot produce a short circuit building a layout.

Another reason was and is the trackbed of Maerklin. I like the prior metal and now plastic bed under the tracks more than without it. That is also the reason I use C-tracks and not K-tracks from Maerklin. And as midwestbls has it so wonderful formulated "Real RRs don't have bumps in the middle of the rail ties" I do not care. So what? Having bumps in the tracks then I am not a real RR? It is a good joke, nothing else.

A third reason is the mfx and mfx+ functionality of the Maerklin decoders. This forces me to use Maerklin digital system. Even knowing railcom tries to develop a feedback system like mfx for DCC too. I do not know very much about it. I think that our community member H0 is much better informed about this system. But then with DCC you even do not have the capability of mfx+. These are good marketing arguments from Maerklin. Well and that is the reason, why they developed mfx+. Wait till all patent protection has gone from mfx+, all the other MRR manufacturers develop a similar system. Because mfx+ makes your MRR to a real train simulator.

This is my individual decision for using AC. Very well aware what Maerklin is writing itself, that within the locos they change the AC to DC or - as by the Swiss “Eidgenössischen Technischen Hochschule Zürich” (ETHZ) defined - digital current. Have a look here:
http://www.itwissen.info...exikon/Digitalstrom.html

If you want to know more and there you are able to understand German (apologize to all the others who do not) I send you 2 links to the

http://www.modellbau-wik...hienen-Zweileiter-System
http://www.modellbau-wik...hienen-Zweileiter-System

The “Modellbau-Wiki”
http://www.modellbau-wiki.de

is established and managed by the MiWuLa owners in Hamburg. Unfortunately it is only in German available – sorry again to all community members here. But it describes plenty of MRR questions in an easy and understandable way. So I want to list it here just for acknowledgement.

Long story and I lost my track to answer your question. Please le me know, if I could give you a better answer or do you still have questions. And please forget it with this provocateur or antagonistic. I am always open for arguments.

I can only see a single "mechanical" advantage: The dreaded reverse loop polarity issue.

The latter is of interest for temporary layout and "Teppichbahning" reverse loops where one wants to do "quick and dirty" plug and play without elaborate reverse loop control automatisms and cabling (and for odd compulsive dogbone track design adepts as my humble being).

To be able to turn a train around so it can travel in the opposite direction on the same track without manual intervention.

There was neither a question in this regard, nor is that an "answer to a reverse loop".

The initial question was: Why does 3-rail AC still exist?
Thats very simple...because there are still people who don't use a digital system.
If hou mean: why does 3-rail still exist? That's another question wich is answered very wel above.
In a lot of cases it's historical. My dad started with Märklin before I was born and I followed in his footsteps
Later when the 2-rail marked was booming and a lot of Dutch models were made, I didn't want to sell all my 3-rail and start over.
In those days I bought a lot of 2-rail models because they ditn't exist in 3-rail. I'm still converting them to 3-raill...
Now I'm stil a '3-railer' using models of all the brands: Märklin, Roco, Mehano, Liliput, Piko etc. powered by the Uhlenbrock IB using DCC for most models and Motorola only for Märklin.

Would I start over in 3-rail when my house burned down and I lost everthing? I don't think so....

Roland: If the train isnt coming back in the opposite direction on the same track,you haven't actually reversed it.

--- That's my point - no reverse loop is needed to have the train come back on a separate track, PARALLEL to the first track, two inches away.

Roland: Think of a Terminus station. A train leaves engine first (pulling it's cars). If you want it to return engine first,you need a reverse loop.

--- The train comes back loco first - two inches over - no reverse loop needed.


I think the real point here is that people LIKE reverse loops and that is fine; but I do believe far too much emphasis is being put on this specific advantage of 3 rail over 2 rail to support the notion that 3 rail is better than 2 rail: beauty lies in the eyes of the beholder.

At risk of repetition: I like having both systems and I would not want to get rid of either.

Have a good Sunday, everyone.

Baggio, a better example that might help clarify... Imagine you have an oval layout. Your train travels clockwise and you now want to have it run counter clockwise. Are you going to double the size of your layout by adding a second parallel oval? A simple reverse loop will accomplish this for you.

Hi,

Yeah, there's nothing wrong in having two different systems. For me it's three-rail AC analogue and digital, though the latter is now limited to DSB locos and Nohab diesels. Some years ago, I thought I should convert all analogue locomotives, but then I realised there's no need to do that. There are still a lot of people who use three-rail in Germany as well as in some other European countries, although the MRR press is biased in favour of DC.

Best regards,
Mark

Hi to All !

Yet ! , There is another reason for choosing Maerklin. Practically all Maerklin' locos have minimum radius for operation ( 360 mm )

Little thing , but nice ...

Take ROCO BR 01, 03, 42, 44 , 50 ..etc. on 360' radius - what happens ?

I had Noch 81500 , it used 360 curves and switches . Using DC ROCO sistem I had the above disappointment .

Edited by user 06 February 2017 07:09:22(UTC)  | Reason: Not specified

Done:
https://www.marklin-user...Dogbone-et-al#post539419

Reverse loops in DC are a non-issue. These have been solved simply for ages using the following type of reverser. I have used them on previous layouts and they are less than 10$ as shown below

Atlas reverser

Thanks for the source.
:o)

I could agree to " neglectable", but for me it would only be a non-issue if none of these devices were needed. In my case, I have seven crossovers which were "polarity"-affected in an 2 rail environment, while currently my cabling consists of a red and a brown cable between the Central Station and the tracks with decoders mounted directly under turnouts and fed by the track. That cabling situation qualifies for me as a non-issue.
;o)

Edited by user 06 February 2017 10:47:20(UTC)  | Reason: Re-counted