How to determine the curve diameter

[walker]

I just received an old Lionel train from my daughter for Father's Day. The freight cars are longer than the ones I have on my current layout. How do I determine the curve diameter that would work for the longer cars? The distance between the center of the trucks varies from 7 to 8.25 inches.

[balidas]

What kind of track did you get?  Tubular or Fastrack? Normally  we get the minimum radius curves with the sets. So if you have the grey molded roadbed that would be 036 Fastrack. If you have tubular then there are two sizes, the low profile would be 027, the taller O gauge profile will give you 031.

[tomikawaTT]

If the cars are larger than those intended for O27, they will probably run on O31 (aka `O Gauge" in Lionelspeak.)  They will look better on O36 Fastrack - but will require more space.

'Way back when, Lionel produced track in sizes O60 and O72, meant for model railroaders who wanted something similar to what our HO brethren can build with 15 inch and 18 inch radius sectional track.  Of course, they require a LOT of room.  These days, folks use three rail flex track to duplicate those wide curves.  They work better on an around-the-wall layout than on a traditional table.

Chuck (Modeling Central Japan in September, 1964 - with 1:80 scale tinplate rolling stock)

[David1005]

If you are talking about freight cars built by Lionel after 1945, they all have couplers mounted to the trucks.  This arrangement handles sharp curves well.  The 27, 31 and 72 inch diameter requirements for equipment generally applied to locomotives and passenger cars only.  For the freight cars, the problem you may run into is with the 027 #1122 switches where the motor is on the inside of the curve.  Some cars may hang over on the inside of the curve enough to hit the switch motor cover.  I would try a car by its self first.  If that works try a train and see if they stay on the track or hits anything due to overhang.

[overlandflyer]

walker

I just received an old Lionel train from my daughter for Father's Day. ...

you could make this process a lot simpler if you would describe the set you received.  engine and car numbers at a minimum might be enough to identify what you have.

using the word 'old' i'll wager that O27/O31 track would be the minimum, but when there is room, always try to do a little better (larger radius) if you can.

[phillyreading]

For switches that better fit with O gauge 031 track, RMT is now selling the old K-Line snap track switches and these have a low profile at the switch, won't hit the motor housing, and fit right in with 031 track. The only modification is to cut the plastic tabs so it fits with regular 031 track.