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Offline Martti Mäntylä  
#1 Posted : 13 February 2019 19:03:53(UTC)
Martti Mäntylä

Finland   
Joined: 15/11/2018(UTC)
Posts: 396
Location: Uusimaa, Helsinki
Last autumn I got in my hands a few Märklin universal relays (7245 Universalfernschalter) and have since been trying to figure out how far they can be pushed.

An article in Märklin Digital Newsletter Sept-Oct 2016 showed the setup of an automatic passing track in digital. This gave me the inspiration to turn the design to analog with the universal relays. I thought some of you may be interested to see the result.

The design takes the following parts:

- Five signals, denoted S0 ... S4 in the switching plan below (S0 and S4 not shown for brevity, they operate according to usual block control)
- Seven circuit tracks c1 ... c7
- Three universal relays u1 ... u3.

And this is the switching plan:



With contact tracks, I am sure the design could be simplified.

The setup works by sensing the relative speeds of the two trains approaching the passing track through the circuit tracks c3 and c1. They turn the universal relay u1 to red and green, respectively. When a train passes c4, the status of u1 is examined to reveal in which order these events took place. If u1 turns out to be red, it signifies that a second train has reached c3 before the first train got to c4; hence, the first train is switched to the side track and the second is allowed to pass. Hence the speeds are sensed through the ratio of the track lengths S0-c3 and c1-c4.

Universal relay u2 stores the information whether the side track is occupied or not. This is used to modify the block control taking place at the exit signal S2.

The tricky part is to make sure that signals do not propagate to cause unexpected results. In this case, the circuit from c5 to S1 needs to be cut when a train is on the side track. This is the sole purpose of u3. The switches of u2 are used to cut the contact from c3 to u1 if the side track is already occupied to make sure that just one train is switched to the side track at a time.

Here's a short video showing the operation with three locomotives:



On the video, the locomotives run in digital mode so that I could set their relative speeds to show the behaviour of the design in a short test track. Basically, BR89 represents the slow train, BR211 the medium speed train, and E40 the fast train. On the video, E40 passes both of BR89 and BR211; if I run BR211 a little faster, it will take turns to pass BR89 with E40. (More varied behaviour is likely to be impossible on a deterministic track.)
- Martti M.
Era III analog & digital (Rocrail, CAN Digital Bahn, Gleisbox/MS2, K83/K84), C & M tracks, some Spur 1
thanks 9 users liked this useful post by Martti Mäntylä
Offline Danlake  
#2 Posted : 13 February 2019 21:14:17(UTC)
Danlake

New Zealand   
Joined: 03/08/2011(UTC)
Posts: 1,571
Hi Martii,

That looks impressive - great work!

I have never used the universal relays and didn’t even know exactly how they works. But after reading your post I got a better idea now.

Thanks for sharing.

Best Regards
Lasse
Digital 11m2 layout / C (M&K) tracks / Era IV / CS3 60226 / Train Controller Gold 9 with 4D sound. Mainly Danish and German Locomotives.
thanks 1 user liked this useful post by Danlake
Offline asp1880  
#3 Posted : 20 February 2019 21:05:43(UTC)
asp1880

Denmark   
Joined: 04/09/2017(UTC)
Posts: 15
Location: Lyngby
Originally Posted by: Martti Mäntylä Go to Quoted Post
Last autumn I got in my hands a few Märklin universal relays (7245 Universalfernschalter) and have since been trying to figure out how far they can be pushed.


Fernschalters are fun. Your side track control seems to work very robustly, well done. And 3 trains simultaneously, nice.

Here’s a similar trifle I put together a while ago. It uses one UFS in the same role as your u1 to “arm” the overtaking system when a faster train approaches from behind.


It’s simpler because it’s only for two trains, but it uses all 3 states of the 2 wing 7041 signal and two trafos for speed reduction when entering the side track.

Regards,
— Anders.
thanks 6 users liked this useful post by asp1880
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