Gargraves Track Diameter and Spacing

There is a method to their madness.  As the diameter gets larger the necessary spacing between tracks get smaller.  The larger the diameter the less overhang you'll see; as the diameter approaches infinity (i.e. straight track) the overhang will disappear.  Ross and Gargraves decrease the spacing with increasing diameter while Atlas, MTH, and Lionel chose to keep their spacings constant.

Jan

@Jan posted:

There is a method to their madness.  As the diameter gets larger the necessary spacing between tracks get smaller.  The larger the diameter the less overhang you'll see; as the diameter approaches infinity (i.e. straight track) the overhang will disappear.  Ross and Gargraves decrease the spacing with increasing diameter while Atlas, MTH, and Lionel chose to keep their spacings constant.

Jan

I currently use Fastrack in my temporary layout but have played with Ross/Gargraves in design software (dreaming about someday building a permanent layout) and wondered about this. Does this hold true even for scale Big Boys, DD35/DD40/Veranda type diesels, etc? I'm imagining a "worst case" scenario where a large loco is on an inner track and a string of 20" or 21" passenger cars are on the next track out

Larger than O-72 can be done with flex track.    4 1/2" center to center track spacing, pictured.

@Mike0289 posted:

I currently use Fastrack in my temporary layout but have played with Ross/Gargraves in design software (dreaming about someday building a permanent layout) and wondered about this. Does this hold true even for scale Big Boys, DD35/DD40/Veranda type diesels, etc? I'm imagining a "worst case" scenario where a large loco is on an inner track and a string of 20" or 21" passenger cars are on the next track out

Anyone have experience with this situation? Is the 4"/4.5" center-to-center enough with 063/072+ radius curves even for large locos and long passenger cars?

With 063/072 you are likely going to be disappointed if you ever want to run two scale big boys in opposite directions.  It will really depend on the size of your engines and rolling stock.  On our club layout we needed wider spacing with min 072 with flex track as the next larger loop.

The overall size of your layout will be a factor.  Suggest using wider spacing from the beginning to avoid future issues.

@Mike0289 posted:

Anyone have experience with this situation? Is the 4"/4.5" center-to-center enough with 063/072+ radius curves even for large locos and long passenger cars?

I try to stick to NMRA RP-7.2.

rp-7.2_curved_track_centers_july_2017.pdf (nmra.org)

Here are some photos using O-72 inner/O-81 outer;

Y3 and GGD 21" car.  Keep in mind the Y3 is a smaller articulated engine.  A Big Boy would hit.

Here are Lionel Centipedes with the 21" cars.  They hit.

Here are the Lionel Centipedes with an 18" car.  Good to go.

I'm using mostly 4.5" on my layout with O-80 as minimum mainline curve, using various Ross/Atlas/Gargraves curves to keep that distance.  I am using flex more.

Even at 4.5" I do not think I can run a Big Boy on the inside track with those 21" cars.  However, my transition era PRR long engines can (just barely) including my scale Centipedes, Passenger Shark, T1, Q1/2, and J1.   I do not have an S1, and my S2 has not arrived yet, so I don't know about them.

Hope this helps.

4.5" is tight, I  have 5.5 with O72 and O84.  I don't have anything hitting, but some come close.

Thanks for all the great responses, everyone. Great info and experience here! I'm years away from having an opportunity to build a permanent layout but I enjoy messing around with track plans in RailModeller Pro, so this is useful information all the same. Hopefully it helps some other folks too!