At last count, I have some thirty analog locomotives that I have no intent of converting to digital, except perhaps one or two I have two copies of.

Every now and then, I'd like to run them around just like my modern locos. I also have quite a few cars for which I only possess a matching analog loco, and they need to get on tracks once in a while too.

Having gotten used to the convenience and expressiveness of digital control - in particular Rocrail - I have been contemplating a setup that would allow me to run trains conventionally while enjoying some of the benefits of digital operation, such as simplified cabling, automatic handling of accessories, and automatic block control.

In particular, even though I think I understand fairly well how to build analog automation using contact tracks, signals, and universal relays, this approach is tedious, error-prone, and only really feasible for a few fixed routes through the layout. Instead of all that, I'd like to enjoy some of the flexibility of true central control such as that provided by Rocrail.

Therefore, I have browsed the net for "analog fahren, digital schalten" mainly to find opinions that it is a bad idea to start with, and it is better to go for full digital. So, I have to go on my own.

To test the idea, I laid a few analog tracks in my otherwise digital Teppichbahn:



In the middle of the layout you can see three blocks named "Analog 1", "Analog 2" and "Analog 3". "Analog 1", in particular, is occupied by the locomotive "BR V 60". As the names suggest, all these blocks are powered by conventional analog track power. Moreover, "BR V 60" is a regular analog locomotive, in fact a BR V60 1009, Variante 3065.01. On the other hand, the six sensors "fb47" to "fb52" (acting as "enter" and "in" sensors of the blocks) as well as the switch "sw15" are managed digitally by Rocrail just like ones appearing in the digital tracks, giving Rocrail a limited degree of control to the analog tracks.

What setup allows me to do is to run the V60 in half-automatic mode with help from Rocrail. In particular, Rocrail takes care of the switch as needed and uses the sensors to keep track of the location of the loco. What I have to do is to run the loco with my white 6647 trafo, i.e., change the direction of the loco at the end of the analog tracks and stop it once it fires the "in" sensor. I can also use drag-and-drop routing just like on the digital tracks. The demo is actually quite fun, giving a new kind of analog driving experience.

I think the demo shows the feasibility of the basic concept of a digital overlay on top of an analog layout. I can see no reasons why it could not be scaled up to handle more complex analog layouts.

Next, I plan to study how I can establish digital block control on the analog tracks by switching the track power of individual blocks on and off using k84 boxes.

I am sure that others have tried similar ideas as well. Please let me know of your experiences!

Hi,
maybe you could use stationary decoders, I don't know if rocrail supports them, this is a decoder assigned instead of a locomotive to a section of track, this way when your analog locomotive would reach the end of the track the software would automatically stop it, the change of direction is something else. Railroad & Co's software supports this functionality.

Best regards

This is quite interessting, and could be useful to me, should I once decide to digitize part of my layout.

I suppose slider-rockers will be needed so that analog power never comes into contact with digital power ?

Also, I wonder if this setup is truly compatible with modern read-back functions as f.x. mfx ? (Given that the analog ground will have to be connected to the digital ground...)

By bad design or being serendipitously broken, one of my old blue transformers (6514 Transformator 16 VA) can deliver continuously 24 volts to the tracks - its control knob remains in the direction change position, unlike other transformers that have some kind of a spring that returns to knob to zero voltage position.

While this characteristic makes the device ill suited for driving trains, it enabled me to continue this storyline one step further.



For this experiment, just two blocks next to each other were sufficient. Like before, their track power is controlled by a K84, shown as the buttons "Track Pow" below each block. The new element are the two new K84 buttons in the middle that control the source of the power, labeled "10V" and "24V". That is, the tracks are connected to two transformers, one providing a mid-range voltage - say, 10 volts - for moving a locomotive nicely along the tracks, and the other (the 6514) providing 24 volts for swapping its direction.

What remains is to set up Rocrail so that these voltages are applied properly to create useful behaviour. I ended up writing an XML macro that applies 24 volts to the track for 500 milliseconds, and after a pause switches to 10 volts. Of course, it is critical that the two sources are never ever connected to tracks at the same time, and I felt it safer to do this in a single macro.



The end result is shown in the video above, which probably is the dullest Märklin Youtube video ever - a single loco moving back and forth along straight tracks. For your pleasure, I at least enabled station announcements in British English, although I doubt they fail to add much entertainment value. Still, the video shows that this thing can be made to work (sort of).

As always, the devil is in the details. As it turned out, the voltage output of 6514 fell somewhat short of 24V. Thus locomotives who switch perfectly with the 6647 white transformer may fail do the same with the 6514. Adjusting the direction changer unit to make them work with lower voltage is possible, but then one runs the risk that the loco will start changing its direction also when run at full speed. The V160 shown on the video, for instance, works perfectly with the 6647 but is jumpy with the 6514.

I have now built a simple analog layout that utilises the ideas described earlier. I nevertheless left automatic direction change out; it was difficult to get it work robustly. I don't mind changing the direction myself.



The Rocrail screen for the layout is shown above. The setup is powered by two transformers. One provides voltage to the main loop controlled by the four signals; the loop runs fully in automatic mode. The second transformer is used to run the inner tracks. Two K84 units switch the power of the eight inner blocks on and off on the basis of route activation.

Although I built the track in my study - a smallish room - I think I should be able to run about 140 cm long trains on it. So the track should offer welcome physical exercise to my 30-some analog locomotives that have stayed in rest too long already.