What is the recommended spacing, C/L - C/L, on straight sections of Lionel tubular, "O" track ?

15 to 16 feet seems to be true railroading. I would try 3-1/2 or 4” centers. That should also cover anything coming out of a curve with overhang.

@romiller49 posted:

15 to 16 feet seems to be true railroading. I would try 3-1/2 or 4” centers. That should also cover anything coming out of a curve with overhang.

Thank you Rod. Sounds good.

Jeff

4” C-C (16 ft) looks good but as said above curves less that 072 will cause interference. I assume you are using PW 022 switches too? If so you will find that crossovers will put the parallel tracks at about 8” C-C. You can reduce this to 5” C-C by cutting the 022’s down to a 30 degree arc instead of the standard 45 degree. This will also make the S curve much less tortuous. Same for a yard, if you use 30 degree switches for the ladder track the siding spacings are 5”; not 8”, looks way better.

To cut the switches down do a search for “cutting down 022 switches” and you should find a topic done a few years back that shows you how to do it. Written by a fellow O gauge track user!

Rod

Thanks, appreciate the additional info about the switches.

Jeff

The answer also depends on whether you want to be able to get 1:1 human fingers in there for uncoupling, re-railing, etc.

Two factors determine CTC: clearance for locos and rolling stock, and CTC for switches used for a crossover.

When the RailKing Big Boy with its big overhangs came out, I determined that 5.5" CTC was a minimum spacing for tubular curves O31 and O42 for clearance with my gear.  YMMV with long passenger cars underhanging on a curve passing the engine.

Lionel FasTrack uses a 6" spacing for O72 crossover switches.

Lionel's tubular O22 switches mate for an 8.5" CTC spacing.

My modular club originally used the 8.5" spacing but later added a third track so now 4.25" CTC is  current.  Our corners are O72 minimum.  When we first added the third track, we ran traditional-sized trains on the middle rail.  We found that by staggering the position of the first curve track (a crude easement), a bit extra clearance is provided so most scale locos and rolling stock can run on the inner and middle tracks.

Ross and Gargrave switches allow closer CTC spacing.  This thread discusses Ross #4 yard track spacing (3.5" CTC).  3.5" is fine for yards, anything less is tight for 0-5-0 switching.

Download an evaluation copy of track planning software (Scarm, Anyrail, RailModeller) to see what CTC stock switches require.

I asked the same question a while ago.  The consensus answer is that you'll be able to run most stuff with 5.5" centers.  I don't have any articulateds, and I don't have a lot of space either.  So a related question that never got answered is, which POSTWAR pieces have the most overhang and underhang respectively (and would thus govern the track spacing?)

My guess is that the cab corners of a 773 Hudson would have the most overhang.  The 16-wheel "super flat car" might have the most underhang.  But excepting that oddball, perhaps a 2625 Madison car would be second?  Or an FM TrainMaster?  EP-5 "Little Joe" Electric??

Underhang is important, because the worst case scenario comes with concentric curves.   A piece having overhang running on the inner loop will gouge the piece having underhang sitting on the outer one.  Of course you can stagger the start of your curves a bit and still bring the mainlines closer together for realism on the straights.  Good subject for discussion!