Replace Lionel contactors

I have six Azatrax MRAPR 12v DPDT 8a relays on my layout rebuild (not MPAPR...maybe a typo?).  

Four of the relays control two crossovers, and the other two relays allow me to run two trains on a single outside loop.  

All the relays are powered from the accessory terminal on my VW, and everything is done using homemade insulated outside and center rails on tubular track.  153 block signals are tied to all six relays.  

Using the relays to allow for multiple trains on the single outside track was relatively easy, and only the relays and insulated rails were needed to make everything (including the 153 signals) work.  The Azatrax website has the wiring diagram for this.  

The crossovers were a little hairier.  It took some trial and error to get things working (mostly) correctly and there were several unfortunate collisions.  Most of the headaches were caused by the coasting distance of the engines running past the "dead" block, then powering up and charging into the occupied crossing.  I increased the stopping block distance which solved the collision problem, but resulted in occasional gridlocks where both trains would encounter a "red" signal and stop.  I needed to install two SPST (momentary on) switches as overrides across the relays to allow one train to "ignore" the stop signal, and proceed through.  I only allow the trains to run in a single direction on the crossover loops.

Overall, I've been very happy using the same process and equipment that you've described above.  It's fun watching trains (and block signals) operate like a ballet.  

Good luck.  

The relay, and a little extra wire, is the only thing you need. If you have the center rail powered by the U post and the outside rail connected to the A post, then connect the relay coil between the insulated rail and the transformer’s C post. This will cause the relay to operate when the train’s wheels are on the insulated rail. On the signal, connect the A post on the transformer to the center terminal on the signal.  Then connect the C terminal on the transformer to the 1C terminal on the relay.  Connect the red lamp terminal on the signal to the 1NO terminal on the relay. Connect the green lamp terminal on the signal to the 1NC terminal on the relay.   The #2 contacts on the relay are extra.  You could use them to stop and start a following train.

Thanks for the replay. Sounds like a nice layout, has given me some ideas.

Great info, will help a lot. Rookie question, what size wire should I use to hook this all up. Thanks

@rph posted:

...This relay seems to be an economical and easy to install alternative to the contactors...

There is another way, using the insulated rail and no relay, just an extra bulb(hidden beneath platform or painted black).

Here is how to do it w/o relays or modules as posted in 2011.