# Diameter of curves

Discussion in 'FAQs' started by CSX, Sep 22, 2005.

1. ### CSXMember

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For my outdoor railway I am getting an Aristo-Craft CSX SD-45 locomotive. It needs 8 foot diameter curves. What is the degree of curve for that?

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180 degrees?
3. ### ezdaysOut AZ way

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Not sure what you're asking here. jetrock is right, 180° for the semicircle, regardless of the diameter or radius. If that's not what you mean, then please be a bit more specific so you can get the answer you need.
4. ### MasonJarIt's not rocket surgery

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See http://www.du.edu/~jcalvert/railway/degcurv.htm

Degree of curvature as an alternate measurement for such small circles (i.e. your 8 foot diameter / 4 foot radius) is almost meaningless in railroad terms. The degree of curvature is/was based on a 100' section of the curve called a chord. It is much easier to refer to radius. However, you can do the math for a smaller circle if needed.

For example, a 1 degree curve (based on the 100' chord) has a radius of about 1 mile. Even a relatively sharp real world railroad curve of 6 degrees has a radius of about 1000 feet.

Andrew
5. ### CSXMember

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Here, maybe this will help a bit. What does it mean when it says the train needs 8 foot diameter curves? I don't want to buy the wrong track for my outdoor railway.
6. ### ezdaysOut AZ way

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OK, it means just that. If you put a peg into the ground and tie a 4' string to it, and trace out the circle the end of the string makes around the peg, that's an 8' diameter. Now if you were working in HO or N scale, you could just go out and buy flextrack and form it to fit the curve. In G scale, I don't know if there is flextrack, if not, you should be able to buy curved sections that would conform to a 4' radius. Someone into G scale would have to tell you how they are marked. That's the best I can do.
7. ### CSXMember

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That would mean buying the track first though?
8. ### Gary PfeilActive Member

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LGB and Aristocraft curved track come in radius's named in diameter, not radius. You need 8' minimum, next size is 10'

Gary
9. ### CSXMember

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I am doing a layout, so how many peices of track come in a diameter?
10. ### 60103Pooh Bah

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You mean in a circle? The number of pieces varies depending on the radius/diameter and the manufacurer. Also, some provide double or larger pieces, and half and shorter pieces.
A full circle of 8 foot diameter requires 8 x 3.1416 feet of track. (The arithemtic is left as an exercise for the student.)
11. ### SLUSSERSNew Member

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How many pieces of track is dependent upon the degree of the section of track not the radius. Some sectional track of the same radius may be made in 15deg., 30 deg., or 45 deg. sections. If the track sections are 15degs., 30degs. or 45 degs., it would take 180 degrees (for one half of a circle)divided by the degree of the track sections.
Examples: 180/15 = 12 sections of track to make a half circle
180/30 = 6 " " " " " " " "
180/45 = 4 " " " " " " " "

Hope this helps. :thumb: :thumb:

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