Lionel Southern Crescent, Blue Comet, Alton - How tight radius?

0-54 is 54" Diameter. The radius would be 27". I don't think they would run on smaller curves.

Fairly often Lionel steam engines can be run successfully on one size smaller than what they specify for a given engine. So I was wondering if anyone has successfully run these Pacifics on O-48 track.

Yes, that's one of the curiousities of O gauge railroading - everyone refers to radius curves, although in truth it's the diameter that is being referred to. Talk to someone about your O-54 diameter track, and he may not know what you're talking about. Talk about 0-54 radius curves, and he'll know what that is.

Yep, ya gotta watch that "radius" vs. "diameter" thing.  Those coming to 3-rail from other scales really have to be especially careful with it because all the other scales describe track curvature in radius.  There's quite a difference between O54 (diameter) and 54" radius (108" diameter).

I believe the catalog says 0-36 for these engines and 0-54 for the passenger cars.

Mine definitely runs nicely on 0-36 Fastrack: including through switches that form switchbacks and all.  No problems. 

 

I have no idea if it runs on O-31, but it does not run on my O-27 tubular - comes close (I imagine if you "spread" the track as wide as you could when setting it up, it would - its very close).  

 

The passenger cars listed for these locos, on the same page in the 2012 catalog, are labeled O-54 only, and probably will not run on even O-48 

I have the Erie K5 USRA Heavy Pacific that was in Vol 1 of the 2001 Lionel catalogue. It was supposed to need O54 curves and when I lost access to wide diameter curves 8 years ago it has been sitting in the closet. Reading comments on this forum about the SRR Ps4 going around O31 tubular track gave me the idea to try it in my O31 layout. Guess what - it runs fine but only in clockwise direction on my layout. So my advice - try a loco on the curves you have - might be surprised on what they can handle.

I have Lionel's previous version of the Southern Crescent and have run it on O31 curves with no problems.

-Ryan

This is a little odd. The 2006 Vol. 1 catalog, showing the Southern PS-4 (same engine as the Crescent), says O-54 for the engine. The new catalog, though, says O-36 for the Southern Crescent PS-4. That's quite a difference.

 

The 2006 catalog also shows separate sale heavyweight cars on the same page, which cars are listed as O-54. It may be that they carried over the car specs to the engine. The 2003 catalog for the previous Crescent says O-54, too, but that was a spec for the set, which would have including the cars. 

 

The new catalog has the engines listed separately from the cars, so I guess they did the specifications apart from the cars.

The old listing says O54 because it canes with the 4 cars. It is the cars that require the wider curves.

I hate it when my phone corrects "comes" to "canes". Also just realized the iPhone app doesn't seem to allow you to correct your own post!

Correct the cars are what require the wider diameter curves. The 2006 engine I have will run on O31 without any problems.

-Ryan