Realtrax O-31 and Fastrack O-31 - same size? Apparently NOT!

I always thought Fastrack was only O-36. That's all I've seen available at least. 

more 0-31 talk here;

https://ogrforum.com/d...ent/4527055129434049

The Fastrack 031 curves are wider than the MTH 031 curves. RRTrack has them available for their program.

Right now, I have an O31 Realtrax loop inside a Fastrack O31 reversing loop and it works fine.  I'm trying to determine if a Fastrack O31 loop will fit in the same spot.  The plastic ballast is about 1/4" apart with the current combo.

Can somebody with rr track put an O31 Fastrack loop inside a Fastrack O36 loop andpost a pic?   I use xtrackcad and it does not have a Fastrack O31 piece to play with.

Ed

Here you go. 031 will not quite fit inside 036 due to width of ballast.

Thanks Mike,

Last night I measured some track.

Fastrack is 3 3/8" wide, Realtrax is 3" wide.

I misspoke, The plastic ballast is about 1/2" apart with the current combo.

Mathwise, using all Fastrack, the gap between tracks should narrow from 1/2" to 5/16" (1/2"- 3/16" = 5/16"), which would seem to fit.  Any idea how accurate the RR track ballast dimensions are?

I run "traditional" size trains and with the current arrangement, cars don't hit (and I usually just have a trolley, plymouth switcher, or handcar on the O31 loop.

I wonder if Realtrax or Fastrack doesn't use center rail to center rail to measure loop diameter... time to break out the ruler again.

Maybe, with a crowbar

Ed

Egads!

I just measured my loops !

Fastrack O36 is 36" from center rail to center rail.

Realtrax O31 is 31" from outside ballast to outside ballast, 28" from center rail to center rail.  That's why it fits inside the Fastrack loop, and verifies that FT O31 probably won't fit inside FT O36.

Hoping my tape measure is wrong,

Ed

ps. that might explain why some MTH locos spec'ed for O42 run on FT O36 - because Realtrax O42 is really O39 center to center... am I missing something?

O-gauge needs standards so bad! It's ridiculous that track circles do not have a common geometric datum.

I have never thought about that. Quite a huge difference in actual sizes. I have too many  Real Trax 031 curves in my layout. I guess in Lionel terms when they say engine can run on 031 curves there may have a problem on Real Trax because they don't measure the full 31. I have not had this problem but was just wondering. 

Fastrack 031 appears to be about 29.75" center rail to center rail. Regular tubular 031 curves match the MTH curves and are about 28.5 " center rail to center rail. Fastrack 031 is 30.5" outside rail to outside rail.

Mike, the math doesn't work for me...

If Fastrack O31 is 29 3/4" center rail to center rail, it need to be more than 30 1/2" outside rail to outside rail, no?

I could believe 31 1/4" tho...

Either way, it appears to be inconsistent with the way other Fastrack is measured.

Does anyone at Lionel have an actual piece of the stuff?.. and perhaps a ruler?

Ed

Lionel's tubular O-31 track makes a nominal 31in diameter circle measured from the outside of a tie to the outside of the opposite tie. Diameter measured center rail to center rail is 28.5in for practical purposes. MTH RealTrax is designed to match this geometry so it can be used in the same space as the O-31 tubular track shown in a lot of the old 3-rail layout books.

FasTrack and Atlas-O 3-rail track measure circle diameters from the center rail to the opposite center rail. So a circle of FasTrack or Atlas-O O-72 diameter track is actually closer to O-73.25. And a circle of Atlas-O O-27 track is closer to O-28.25, which is why a lot of "Minimum Curve: O-31" equipment will go around Atlas-O O-27 track, but not tubular O-27, with is actually around O-25.75 using a center rail to center rail measurement.

Unless Lionel decided to 'break the mold', and keep the tubular O-31 geometry with the FasTrack O-31 curves, I would expect them to be O-31 center rail to center rail

All we know right now is what RR-Track produces in its program for track design.

If the Fastrack O31 is as portrayed in the program, it does not conform to any previous O-31 metrics from any manufacturer.

We'll know more when it is delivered.  There may be a logical reason for this "oddball" curvature (per RR-Track), or it might not even be that size.

  --Joe

While RRTrack might be wrong, I have not found this to be the case in the past. What RRTrack shows is that MTH 031 curves match modern 031 tubular, and Fastrack 031 curves match the geometry of prewar 031 tubular curves. Prewar 031 curves had a larger diameter than modern 031 tubular.