Wiring help, 2 trolleys sharing one line

So looking for some electrical help with some wiring reccomendations on our new layout.  I would like to have two trolley cars run on the same out and back line. These are both bump and go trolleys.  


My thought was to put a switch at one end and be able to park one trolley on each side. Looking for a circuit that will only power one trolley at a time. So when trolley a pulls past the switch, power is cut and then transferred to trolley b.  Also would like to be able to control it with a 3 position switch to run A/B on their own or both. 


Anyone have any thoughts?  My googling and searching the forum hasn’t been much luck. 

-Nothing runs like a Deere!-

Original Post

Some might suggest this is a great Arduino (microcontroller) project but I figure if you're knowledgeable about that method you would have already done it and wouldn't be asking!

The "classic" inner-outer loop with two engines comes up every few years on OGR.  Here's a video of manually controlled operation from this thread

In your case, you just draw a vertical line and "cut" this layout in half for out-and-back.


I know I posted a video on a thread on the automated alternating version but I can't seem to find it just now - probably was from before OGR changed to new host so the video and thread are gone. 

The "trick" with the automated version is getting a reliable momentary trigger.   Specifically, after an engine triggers the other side, the trigger must vanish by having that engine mechanically coast past the trigger sensor as power is cut.

Because of bump-and-go reversal, I believe the easiest way to effect a reliable momentary trigger is with timer modules to let a particular trolley exit the siding and go onto the mainline.  In other words, you want the trolley to enter the mainline before "enabling" the trigger that will fire when that trolley returns to the siding...and while one could dream up logic-circuits to do so I think the easiest is to give the trolley 10 or 20 seconds (or whatever) to power up, leave the siding, and enter the mainline.  After this delay, the trigger is enabled so that when the trolley returns it will effect the power switching to the other siding.

As illustrated in the video you can use anti-derailing of the turnout which handles the mechanical steering for "free".

I'd say it can be done for, say, $10 in eBay modules...maybe even without soldering.  No problem to insert a mechanical switch to disable alternating A/B action to operate just A or just B.  It all comes down to your DIY skill/interest.  To pursue further, I'd be interested in your exact configuration - transformer, track type, dimensions, trolley models.  Is this even 3-rail (so that insulated-rail triggering can be used)?  And so on.


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Thanks Stan, sorry I didn't include more in the post as I was posting from my phone.  A couple additional comments:

  • Am running the layout on an old lionel ZW.  Need to get the whistle rectifier upgraded but appears everything else is in working order.
  • Running Lionel tubular track
  • Trolley line is an out and back, it is about 16 feet long, and uses 2 trestle sets to run up and over the mainline for the rest of the track.
  • Will be running a Lionel 060 trolley that my nephew is getting for Christmas, and a 6-8690 that my grandfather bought me 20 years ago.


I'll read through the other thread and see where I can go.  I'm not at all afraid of wiring and trying things.  I spend most my days working on DC systems on Agricultural equipment, but for some reason AC really throws me for a loop doing these things because I'm not as familiar with the components.

-Nothing runs like a Deere!-

JD_Reith posted:

.. I'm not at all afraid of wiring and trying things.  I spend most my days working on DC systems on Agricultural equipment, but for some reason AC really throws me for a loop doing these things because I'm not as familiar with the components.

Not to worry.  What I'm imagining is a DC system (12V) with all the logic, timing, etc. being performed with off-the-shelf 12V DC relay and timer modules.  I was making some chicken-scratches on the proverbial back-of-an-envelope and I'm thinking maybe $10 (free shipping) in eBay modules and parts. 

I'm imagining 6 wires from the track/layout as shown below.  ZW "hot" power would be switched to the A or B sidings which means you would need to isolate power to the two sidings using insulating/fiber pins to create power blocks.  Additionally, within each siding, you would create a section of insulated-outer-rail which would be used for occupancy detection which triggers the swapping of center-rail power to the other side.  A 3-position switch selects A-only, B-only, or alternating A/B operation.  The relay modules would be powered by a 12V DC wall-wart.  I think it can be done with minimal soldering (perhaps just 3 solder connections to the 3-terminal switch).  

alternating out-back trolley

The relay modules have screw-terminal inputs and outputs so no soldering required there.  The trick of course is defining the inter-connections between the modules.

The basic idea for automatic alternating operation is as follows.  The mainline is always powered.  Suppose siding A is powered.  Trolley A leaves the siding enters the mainline and when it returns to siding A it trips the A-side isolated-rail and power is swapped from siding A to siding B.  Trolley A stops.  Trolley B starts up.  Trolley B has to run to its bumper, reverse, and then leaving siding B.  This takes, say, 10 seconds.  The "trick" is to disable the siding B occupancy sensor until trolley B has left the siding and has entered the mainline.  That's the purpose of the time delay relay modules which waits, say, 15 seconds before enabling the occupancy sensor on side B.  Non-derailing in the turnout switch will automatically set the turnout direction as trolley B enters the mainline.  When trolley B returns to siding B, the occupancy sensor has now turned on and power is swapped from siding B back to A.  Lather, rinse, repeat.

I figure about $10 out of pocket.  Anyway, does this make any sense at all?  It is somewhat involved and as suggested earlier, is DIY rather than plug-and-play.  I can provide additional details if your eyes haven't glazed over.

Of course if someone else has a simpler solution, let's hear it! 


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I think this makes sense to me actually, not sure why I didn’t think about doing it in DC.  The timing relays should work as we intend to always run the trolley line at a fixed voltage  

Im gonna have to try and draw this out tomorrow. One question though, how long of a section of insulated track do you think should be used? Wasn’t sure if it mattered or not. 

-Nothing runs like a Deere!-

You could do it with a lone 2 pos. e unit + 2 isolated rails. You can use what you like really.

  You know some agricultural equip? Relays, saftey loops, etc.. Your general "switching & wiring knowledge" is still pretty applicable.  Mostly; wiring is wiring, (and switches included....: isolated rails are just a funny switch ))

 Staggered movents, but they just sort of "catch up" to the original starting position and continue the cycle from there

  It requires a powered block beyound the stopping block that is long enough for the trolley to reach bump speed from a dead stop; and the isolated rail needs to be centered along each stop block.

A delay is only needed at stops where there is one trolley/siding !

   Where there are two trolleys/2siding at a station, one has been sitting waiting, loading.

  Here's your story, keeping in mind the flow of people is greatest on exit and a good station flows well....      Insufficient funds forbids upgrading the amperage  capability to your traction line and it is only designed to run one trolley at a time, but for station efficiency they use two! For a P.R. spin it is also billed as a conveince and saftey protocal only one trolley moves so a wreck can never happen and you can wait for your departure sitting in the windfree shelter of the trolley cabin.

T-1 arrirves back and t2 leaves immediately. T1 waits for its next departure. t2 come back; unloads. While the platform is full of #2 arrivals, t1 bumps and stops; now staged for departure but waiting breifly for stragglers while t2 bumps and stops now ready to load, so t1 leaves........

With two, 2-siding stations and two 2-position e units, you can run three and they will "juggle" platform postions. 

You might even be able to work this out via the anti derail features on the turnouts.... I'm not awake enough yet..... maybe later...

"Still trying to not shoot my eye out"


"Nursing insomnia one railcar at a time"

My aroma therapy? Smoke Pellets.


JD_Reith posted:

.. One question though, how long of a section of insulated track do you think should be used? Wasn’t sure if it mattered or not. 

alternating out-back trolley definitions

I may be misunderstanding your question, but in my scheme there are two types of insulation.  First, the center-rails of each siding must be isolated into blocks.  So as shown above, the orange center-rail (A-siding) can be powered/unpowered.  Likewise, the pink center-rail (B siding) can be powered/unpowered.  The mainline red center-rail is always powered.

Additionally, you have the insulated-rail triggers.  There is a lot of flexibility here.  In general, the yellow section only needs to be shorter than the orange section.  It can be just a few inches long or basically long enough so that when the trolley reaches it, the trolley wheel axles will "reliably" short the outer rails to generate the electrical trigger.  As the trolley enters the siding from the mainline, as soon as it hits the insulated rail section (yellow or light blue), it will lose power and coast to a stop...probably in just a few inches but depends of course on initial trolley speed.

In my scheme, when a siding powers up, the trolley must continue to the right, hit the bumper, reverse, start going left and enter the mainline within some number of seconds (say, 10 seconds).  This is where the time-delay comes into play.  The time-delay disables the insulated-rail trigger giving the trolley time to startup, bump-n-reverse, and exit the siding.  You cannot place the leading-edge (left-side) of insulated-rail trigger too close to the bumper or else when you power up a trolley it will not have enough acceleration zone to get up to a fast enough speed to reliably hit the bumper and reverse.  This is probably only about a foot or so but again depends on how much fixed AC track voltage you use.


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alternating out-back trolley Rev 1

So here's one way to wire up the contraption using about 10 bucks in eBay relay modules and minimal soldering required.

alternating out-back trolley using eBay modules 10 bucks

6 relays are used to perform the logic, sequencing, and power switching.  2 of the 6 relays have time-delay capability. 

As proof of concept, here's a short video showing the automatic switching operation to the shared mainline.  I don't have bump-n-go trolleys so you'll have to use your imagination.  I also don't have the exact relay modules recommended so used 6 relays of an 8-relay module I had.  I also don't have the time-delay relay modules as recommended so there's a bit of circuitry sitting on top of the 8-relay module to add time-delay to 2 of the 8 relays.

I don't know how much "theory of operation" is appropriate but the "trick" if there is one is relays #1 and #2 are wired up to be a latching relay.  One trigger "sets" the relay, a second trigger "resets" the relay.  Yes, one can indeed buy a 12V DC latching relay on eBay with screw-terminals (no soldering required) but it's over $10.  Likewise, one could cobble together latching and timing circuits using digital IC chips which could actually save a couple bucks in out-of-pocket cost, but then this would require wiring up and soldering tiny electronic components.

The other technical tidbit is the positive +12V DC power is tied to the AC outer-rail common.  In other words, when the axle reaches a trigger zone, it provides a +12V DC trigger to the relay circuitry.  This active-high or positive logic makes it easier to work through how the circuit works.

If you locate the trigger zones close enough to the siding bumpers, one could replace the $1.78 60-sec delay relays with 99 cent 10-sec delay relays.

delay relay up to 10 sec

If a trolley can power up, start going toward the bumper, bump-n-reverse, and clear the trigger zone within 10 seconds, then this less expensive delay-relay module could be used.  This goes to the previous comments about where in the siding to locate the insulated-rail trigger zone.


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Traditional O22 style switches have this capability built in!

1) Assemble your track. The key here is to add an additional insulating pin on the center rails leaving the straight and curved paths from the switch (but not the base of the "Y").

2) Run track power (say a lockon) to the line at the base of the "Y".

3) On the switch motor, there are 3 terminals - take an end terminal form the switch machine and run it to the center rail of one of the paths leaving the switch. Then do the same for the other terminal and other path leaving the switch.

4) Wire up the O22C switch controller as normal. This can be used to control which trolley line is active.

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