[tkruger]

Just curious as to what O27 means. I know that in HO 18r means the turn has a radius of 18 inches. Last O27 set I saw looked like it had a turning radius tighter than that of the average HO train.

 

[Big Ed]

Just curious as to what O27 means. I know that in HO 18r means the turn has a radius of 18 inches. Last O27 set I saw looked like it had a turning radius tighter than that of the average HO train.

8 pieces of O27 curves make a circle 27 inches in diameter, hence the name O27.

 

[tkruger]

8 pieces of O27 curves make a circle 27 inches in diameter, hence the name O27.

Thanks, so in HO that would be an 13.5r turn.

 

[T-Man]

For 027 the diameter is 27 inches from the outer rails, a 13.5 radius.
O gage track starts at a 31 inch diameter.
You caught me with my tape measure out, ED.

 

[Big Ed]

For 027 the diameter is 27 inches from the outer rails, a 13.5 radius.
O gage track starts at a 31 inch diameter.
You caught me with my tape measure out, ED.

I thought whatever the number is that's the inches of the circle.

Example O/54 is 54" O/72 is 72"
The only difference is the amount of track it takes to make the circle.

16 for O/54 and O/72 is I think 16 too.

 

[swavk]

diameter

One additional note. The actual diameter varies by manufacturer. The actual measurement is somewhere just outside the outer rail to somewhere around the center rail.

Go figure.

 

[tjcruiser]

Tkruger,

A couple of other points ...

O track is sometimes referenced to center of rails, sometimes to outer rail. O27 is 27" diameter to outer rail. O72 is 72" diameter to center of rails. Also, remember that the rail cross-section of O27 and true O track is different ... smaller "tube height" for O27, larger "tube height" for O.

You might want to read this thread, too ... O vs. O27 ...

http://www.modeltrainforum.com/showthread.php?t=3566

Regards,

TJ

 

[tkruger]

Thanks for all of the comments. I was just curious about how other gauges worked. I have always used HO and had little knowledge of O27. Altho I do not have the room for an O27 layout at this time I still want to learn about it. If I ever get a chance to make a track around the ceiling of my train room that will be O27.