Minimum Radius Question

When Gilbert switched to Pikemaster track with a smaller radius, they shortened the steps on the GP-7 so the coupler had clearance. The new FlyerChief GP-7 might be O.K. as the pilot steps turn with the trucks.

The smallest radius track made by Gilbert was the 15"R Pikemaster track. As mentioned above the Gilbert GP7 with the steps removed worked. All the engines sold as Pikemaster will work on 15"R. those are the F3's and a few steam engines. Don't know about 27" diameter, a few might. All the new production from Lionel is advertised for 36" diameter track.

I have almost all of the AM diesels down to the SW1. None of them will run on Pikemaster. It may be possible to hack them up to make them work at 27" diameter. I have a new GP7 with movable pilots but it would not run on 27" diameter. I do not have a new Baldwin.

AmFlyer posted:

 All the new production from Lionel is advertised for 36" diameter track.

That would be 20" radius (40" dia) or R20.  O36 is some weird catalogue thing that has been going on for a few years now.  They state O36 for minimum when that doesn't exist in S.  Not sure if their intention is 18" radius.  There are R20 and R27 curves.  Using the "O" nomenclature, that would be O40 and O54.  

Brendan

It is risky to say Gilbert 20”R track directly compares to O40. The reason is the O gauge diameters are center to center. Gilbert diameters are outside to outside. Modern S gauge sizes are sometimes center to center, sometimes not. Seems to depend on the brand and if it is high rail or scale. As Brendan says S36 does not exist despite the advertised numbers. Lionel means to say it works on modern S gauge FasTrack or original Gilbert track.

Yeah, probably a poor comparison.  I believe fast track is measured center to center and the tubular was outer? 

Brendan

The Gilbert and K-Line (later acquired by Lionel) are outside diameters. SHS stamped the boxes as 20"radius so they were outside as well. Lionel FasTrack is in the catalog as 20"R so that is also an outside dimension. American S Gauge is sold as 19"R so that is likely center to center diameter. I think AM is also centerline. I have no idea what the GarGraves 42" diameter track is since I do not own any. My conclusion with S gauge is the only way to be sure is to build a circle with the track and measure it.

The good news is 19" vs 20" radius rarely makes a difference when we build layouts.