# How is the radius on track measured?

Discussion in 'FAQs' started by Fusion, Jan 6, 2006.

1. ### FusionNew Member

I'm planning out my layout and would like to know how to measure the track. For example on Atlas track packaging it says 12.5" Radius/Full Curve. What does this mean exactly? And on that note, if I use Atlas Flex Track should there be a minimum radius curve that has to be followed?
2. ### 60103Pooh Bah

Fusion:
Radius is measured from the centre of the circle to the centerline of the track. This makes it easier to draw track plans, but you have to remember to add space for the bits of track on the outside.
"full curve" is a marketing term. Someone decides that a certain number of sections will make a circle -- usually 12 or 8, sometimes 6, 4, or 2! That size becomes a "full" curve. Half that size becomes a "half" curve, then other fractions. Often wider curves than minimum will be allowed to take more than 12 sections to a circle -- usually this keeps them about the length of the first full curve, and keeps tha packaging the same size. (Did they tell you I'm cynical?)
Minimum radius is an artistic decision. Well, it depends on what type of lcomotives and cars you plan to run and how much space you can occupy. 12" in N gauge should allow you to run up to middling sized diesels and steam locomotives with 6 drivers, possibly 8. (will depend; some highly detailed locos may need much wider curves.) I ran full length passenger cars around 12", but if they were spaced closer together it would have required wider.

Atlas flex track should curve down to something much sharper than you could possibly want. When Peco Streamline first came out, they showed the track twisted into spirals and tied into knots.
3. ### FusionNew Member

Thanks 60103. Now it's making sense.

Now on a curve how far appart will multiple tracks in N scale have to be? I've read some posts on this but didn't find a definitive answer. I think someone said 1 1/4" or was it 1 1/2" from centre to centre of the track.
4. ### ezdaysOut AZ way

1 1/2" is OK on straight runs, but you might want more on curves dependent on what you're going to run. You've got to make sure you have enough clearance for any overhang so that one car doesn't touch anything on the adjacent track. The length of the longest car or loco you're going to run will also determine what the minimum radius should be.
5. ### 60103Pooh Bah

How far apart depends also on curve radius. Things stick out more as curves get sharper. You can get an idea by putting down a curve and taking your longest car. Run the car around the curve with a pencil on the outer corner and again in the middle of the inner side and marking where it runs. (a pencil lead might be better if it doesn't keep breaking.) This shows how much overhand there will be. Try with a few other cars as truck pivot points affect things. If you have big articulated steam locos, the front ends do interesting things on curves.