parallel track clearance

I'd personally go for around 5" center to center.

4.0 or 4.5 on straight,  5.0 on curve.

Are your O54 and O72 curves equal spaced (some say parallel)?  If they are then your parallel straight tracks would be 9" apart.  That is plenty of room to allow you to run most anything that can run on O54 track, as well as everything that is available on the O72 track.

My layout has O-54 and O-72 radius track and I have no issues with it, as they are generally not parallel through the curves.  Here is a photo of the layout.  Note the outer loop is Standard Gauge 72 radius, then O-72, O-54, and then regular O for the dogbone loop.

I guess it is a matter of how close you want to space the tracks.  My Standard Gauge loop has 1 straight section at the middle of the curve, where the O-72 loop does not and the O-54 loop also does not have any straights in the curves.

NWL

I think the OP wants to know how close they can be without a collision as he's putting up a ceiling track.  Having that kind of spacing is not in the card I suspect.

@OTS posted:

...what is a minimum distance between parallel tracks on curves of O54 - O72 ?   I'm considering a shelf layout and I want to be a narrow as possible to lessen the leverage weight of the outside track or when two pass each other.

@gunrunnerjohn posted:

I think the OP wants to know how close they can be without a collision as he's putting up a ceiling track.  Having that kind of spacing is not in the card I suspect.

Then maybe he should consider using the same radius track on both loops and having a straight section (either full or partial) at the middle of the outer loop to space the outer loop a bit wider for the inner loop.

Most, if not all, folks on the forum will tell you 6" center to center is safe for pretty much any loco and rolling stock ever made. Anything tighter than that, especially for curves less than 072, will have to be tested to make sure the spacing accommodates what you're running.

With most track systems, a double mainline with 6" center to center will take up about 10" of width.

Also if you research this topic on the forum research tab, there are numerous posts and pictorials to help you make your own decision.

If you have the track, put it on the floor and experiment.

@gunrunnerjohn posted:

I think the OP wants to know how close they can be without a collision as he's putting up a ceiling track.  Having that kind of spacing is not in the card I suspect.

Concur with that

OTS, if you are going to do something like below, then with these size curves I think John is correct in that 5" is good.  If you use smaller curves, you will need to go to 6".  As Mike mentioned, you may want to test your trains first on a floor test layout to make sure.

Based on my MTH K4 you are good with 4" center to center spacing on curves as long as you don't run longer than 18" passenger cars, 50' boxcars, or a schnabel car, or a crane car.

-Greg

Greg, thank you for the reply.. on my AnyRail plan it appears that I am 4 3/4" center to center on the straight section and it opens up a bit into the curve.

Thank you CAPPilot.. what I've done different than the image you provided ..I used identical curve sections and made adjustments in the straights to have a nice flow. The straights are 4 3/4" on center but, they do open up into the curve using the same curve. Great idea about setting up some track on the floor and checking out for sure what two locos do on the approach. Thanks again.

CAPPilot.. I'm using O63 on the curves.. and adjusting the separation on the straight section..which ( the straight section ) seem to be 4 3/4 center to center.

Gunrunner John.. Here's what's happened. Going into "O" for the first time I created a plan to take up my 19'x13' footprint. I really liked it. But, I couldn't pull the trigger on dismantling my HO shelf layout.. So, I decided to go around the ceiling and come off the shelf into a 13'x6' descending mountain using loops and figure 8's down to about 42" from the floor. My local hobby shop advised me to go multiple loops instead of just one track giving more action and attraction. Never having done this scale..feeling the weight of the two locomotives I have now.. I'm concerned going too wide on the shelf for two reasons.. the leverage put on the wall anchors and if I go two tracks I will probably elevate the one closest to the wall so you can see that track better. That's the plan.. SMH..lol.

Atlas track curves are 9" Diameters. O27, 36, 45, 54, 63, 72, 81, etc.   Center to Center track spacing, 4.5 inches.

@OTS posted:

Never having done this scale..feeling the weight of the two locomotives I have now.. I'm concerned going too wide on the shelf for two reasons.. the leverage put on the wall anchors and if I go two tracks I will probably elevate the one closest to the wall so you can see that track better. That's the plan.. SMH..lol.

I think you'll find that any decently supported one foot wide shelf will easily support two good sized O-gauge trains comfortably.  Even decent drywall anchors will support 50-60 pounds.  I don't recommend that, I'd make sure I was connected thoroughly to the studs, that should alleviate any issues with weight, assuming the actual shelf and supports themselves were up to the task.  I wouldn't be that concerned about the weight handling of the shelves providing good construction practices are used in their creation.

I went around the room with a pretty decent stud finder and put tape on the wall showing the edges and center of the studs..  Thanks again for all of your help.

the way I do this is tape a marking pen to the front and mid-pt  on your largest car or engine so that the pen points hit the track mounting surface. Move the car around the layout marking the clearances for the track as a pen line.

do this on adjacent tracks. Where the pen marks overlap you have a clearance issue. So at those overlap parts move the track at that point and re-mark the track surface until there are no overlaps.

using pens taped to the car has the advantage that the actual clearance is increased due to the diameter of the pen and that the point sits 1/2 that diameter distance away from the car. the smaller the pen diameter the closer the clearance.