Mixing O and O-27?

The #1 cause of the issue you're describing is a loss of good electrical conductivity between apparently connected track sections.

Assuming you're using 3 rail O track, the 2 outer rails are typically Common (negative if you prefer) and the center rail is Hot.  So unlike 2 rail systems, there's no electrical polarity concern with loops that return back on themselves.

Solutions are to first:

1. Tighten the rail connections around track joiner pins. This can be done with a pair of pliers.
2. Then add more electrical drops along the track.  Typically using a distribution block to split each of the Hot and Common wires coming off the transformer so that wire pairs attach to the track roughly every 6 track sections.

Okay. That is good news. Thank you.

You probably have already observed this...  if you're inserting O27 pins into O gauge rail, they won't make good contact because O27 pins are smaller.

I'm not sure whether Lionel ever made a "transition section" to facilitate connecting the two.  But you should generally shim up the O27 track to the height of the O gauge.  Make sure the alignment is spot-on, and use at least one track screw to anchor each of the opposing sections.  Ensure good electrical conductivity by adding jumper wires-- at least one for ground and one for the center rail.  If this is a temporary holiday layout, you could use two lockons instead of soldering.  My $.02.

I've inserted a short  piece of bare copper wire under the insulator paper on the center rails of problem joints.

Jan

You show 2 transformers.  Have you split the track into blocks, at least 2 electrically separate sections where only one transformer at a time is in control of each section?  Is your drawing depicting a double track layout with 2 independent tracks?  You solved the pin size issue, the other is that O is taller than 027 and might need a shim at the meeting point.

Wait, sailing season is over?

You can force O gauge pins into O-27 track, but can't use O-27 pins to mate with O-Gauge track. I mix the two successfully on my layout.

My Lionel Bascule bridge has O gauge track on it, but the layout Uses O27 gauge track (O42, O54 and O72 curves).

I use O pins with half of their length ground down to O27 pin diameter. Great for transition.

If you are using O27 height track with O height track, the O27 will also need to be shimmed to the O height

@CALNNC posted:

You show 2 transformers.  Have you split the track into blocks, at least 2 electrically separate sections where only one transformer at a time is in control of each section?  Is your drawing depicting a double track layout with 2 independent tracks?  You solved the pin size issue, the other is that O is taller than 027 and might need a shim at the meeting point.

No, They are not split.

@Jan posted:

I've inserted a short  piece of bare copper wire under the insulator paper on the center rails of problem joints.

Jan

Insulator paper?

via GIPHY

You are all great, thanks for the feedback.

@Kellllly posted:

Insulator paper?

Insulator paper is wrapped around the center rail; the black/brown ties are crimped around it.  One piece at each tie to electrically insulate the center rail from the outside rails.

@Kellllly posted:

No, They are not split.

Now I am confused, unless on your drawing you just drew 2 transformers.  If you actually have 2 connected all the time feeding one track not divided into separate blocks where you are back feeding one transformer into the other, that can be a big problem.  Maybe you just drew 2 on your drawing.