Track Spacing

My Layout is a minima of 4 inches on the center rail, for parallel straight track.

I have used 4 inch spacing on side by side straight tracks. Spacing on curves can get a bit critical as the engine overhang(steam engines[big boys-4-8-8-4] have larger overhang, cab and/or tender steps) will need to be factored in as well. If you have an 031 curve the next size should be either 036 or 042 and be spaced at least 5 and a half inches maybe even 6 inches center to center.

Lee Fritz

Salvaging,

For straight track you could get by with as little as 3 1/2", 4" is common on layouts I've seen.

For curves, there are just too many variables to answer your question without a lot more information.  You need to determine:

- the minimum curve you plan to use on the inside track Of your double track loop.

- the largest/longest engine you ever expect to run on your layout; specifically what is it's outside overhang for the track radius you plan to use?  Let's call this overhang "X".

- the longest car you ever expect to use on your layout; specifically what is its inside underhang for the track radius you plan to use?  Let's call the underhand "Y". 

Once you have this info you can determine the minimum track center-to-center you will need for your layout by adding X + Y.

For example, the minimum inside track radius on my double track loop is O81.  On that radius, my longest engine has 3" overhang and my longest passenger car has 1 1/2" underhang.  That requires a 4 1/2" minimum center rail to center rail distance.  So my outside track radius needs to be O90 so that the engine on the inside track and the car on the outside track don't hit.

Your layout needs will be different depending on your curve size and engines/cars you plan to use.

@ Salvagni  The minimum distance of double track centers is 3-1/2" and 4-1/2" on curves as per The Model Railroader Cyclopedia, Fifth Edition, 1948.

Paul,

For 2-rail O scale models that makes sense for curves if you have large diameter curves.  For 3-rail models, especially engines with blind drivers and cars with truck mounted couplers,I don't think that rule is applicable.  Does it work on layouts with O36 curves and large Lionmaster or RailKing articulated engines?

Truthfully Ron I don't know. We don't have .036 curves on our layout at NJ Hirailers.

However, the measurements I mentioned work very well on well on the larger curves we use that the Lionel Vision Line Big Boys run on. 

The plan I'm working on for our club will have 6" center to center or better. Ross has the right sizes starting with 72 inch. This will allow clearance with all the large items. If youre dealing with 036, then it seems the standard manufacturers separation would work because you wont be able to run the big stuff anyway.

As far as Scarm tape measure. Its very accurate because it has a pinpoint to place on the center line or endpoint of track or wherever.  Just remember to use your scroll wheel to enlarge the plan to get the accuracy you need for placement.