How is track diameter determined from the various track vendors

they are all close enough its not going to matter......atlas increases 9" at a time ...you will have 4 1/2"between track no matter how you check it.....jim

That might not necessarily be true.  Now, I'm basing my info off what I've found using SCARM.  In that program, the Gargraves 072 is different from the Lionel 072 which is also different from the Ross 072. 

From what that program shows, assuming it to be accurate, Lionel looks like outside rail to outside rail, Gargraves is middle to middle, and Ross is inside rail to inside rail.  Haven't checked to see what Atlas shows up as. 

Dom,

That is exactly the reason for my question.  When I put O-72 in RR track and draw a circle of Ross, Gar Graves and Atlas, It looks like O-72 for Atlas and Ross is measured from center rail to center rail, where as Gar graves looks to be inside rail to inside rail.  Looking to confirm this in reality.  

This would helpful to know when mixing the track types, which I assume most do for ross and gargraves

Mke

Most use center-to-center.

Ross and Gargraves use radius. Atlas, Lionel and MTH use diameter, except for ScaleTrax(check that one).

The other variation is from the geometry design. 4.5 5.5 or 6 inch center-to-center spacing or some in betweens when connecting two switches for a crossover and set the spacing using required extensions(if any).

So, an 036 radius is the same as an 072 diameter track.

Note: In SCARM, the curve extensions for Ross switches are not in the Library yet. RR-Track has them.

Comparing Gargraves track to Lionel tubular track I can say that Gargraves has a slightly larger track diameter then Lionel. The Gargraves 042 track is closer to 43 inches then it is 42 and the Gargraves 072 might be closer to 73.25 inches when compared to Lionel track.

Not sure about the Ross switch extensions but the Gargraves switch extensions for the curved piece are about half of a regular curve section.

FYI, Gargrvaes switches are not the best for use with MTH engines as I have trouble with Gargraves switches and derailments with MTH engines.

I can use Lionel post war 022 switches and K-Line 042 switches with my MTH engines and not have problems but I don't like the Lionel switches because of their current poor quality.

Lee Fritz

Mike one thing you will find about O-gauge toy trains, there is no standard across manufacturers.  The one exception is that the dimension between the outside rails is 1.25-inches which at 1:48 equals 5 feet not 4' 8 1/2".

Now as I recall in my days using Lionel tubular track they measured across OD.  

Now GarGraves publishes their spec.  And GarGraves in fact specifies in diameter not radius.  Listed are the DIAMETERs center rail to center rail for the GarGrave I use most.

72   72.59"

80   79.76"

89   89.31"

96   96.47"

I also use Ross curve sections to mirror image where I use Ross switches.  As I recall Ross curves are generally tighter than GarGraves.

And it has been so long since I used Atlas I forget my dimensional findings.

Best thing is the contact each manufacturer for their info. GarGraves is available on their website.

Ron

Along this thread-

Does anybody have an "O-72" Lionel fastrack layout and can they tell me whether the 72 inches is from center rail to center rail or from the outside of the railbed to outside of railbed?

I have a 6x8 table and before I buy a bunch of 0-72 fastrack, I would like to know whether I can make a O-72 circle fit on the table or whether the track and/or trackbed will be hanging off of the sides.

Thanks.

- mark

FasTrack is center rail to center rail.

DrTrainDad,

It doesn't fit. You need a 7 x 8. 72" center to center + (1 3/4" x 2) for roadbed=75 1/2". 060 will fit. (click on the pic)