Now how about curves.


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I know there is a way to apply a radius to a curve section of track, but how can I tell what radius to apply? I have a track chart that shows the curve as 2" and 1 degree 00'. How do I turn that in to a number to plug in to surveyor? Thanks for everyone's help with the straight track portion.
eerbaugh, Short this time I promise. Degree of curvature is a way to specify the radius of the arc. Used by surveyors as a way to mark out large radius curves. It specifies the angle deviation in degrees measured for a 100 ft arc length or chord length. Unfortunately they're not exactly equivalent but for Trainz it doesn't make much difference which one you use. RR's typically used the chord method and highway surveyors typically the arc method at least in the US I'm told but it varied.

1st the degrees of curvature are usually given in degrees and minutes of arc. Convert that to degrees and decimals:
D = d + m/60

2nd for the arc method:
R = 5729.58/D for R in feet
R = 1746.38/D for R in meters

or for the chord method:
R = 50/sin(D/2) for R in feet
R = 15.24/sin(D/2) for R in meters
be careful using the above since D is given in degrees - many calculators and programs may require degrees converted to radians before using in trig functions (D in radians = D/57.2978).

Now you're on your own because I don't know of any way to get Surveyor to create a constant radius curve for you. If you can locate the center of the arc you can swing a ruler and mark points along it as I mentioned before or you can calculate points along the arc like surveyors do from the point on the tangent track. Others might step in here and give you some other methods they use.

Good luck,
Bob Pearson
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Hi Bob,
Avery well written explanation, I will get back with a method of doing it. I have to make some diagrams.

well i usually use Fixed track curves Just to get the Curve looking pretty nice and Delete those Fixed track After adding the Track of Choice, this works pretty well for me :)
Smooth Curves

Hi eerbagh and Bob,

Here goes, hope I can get the screenshot links to work.

1. Start from a straight peice of rail, i.e. use the straighten track tool on it.

2. Next lay a ruler at 90 degrees from the straightened track on the side it is going to curve too. Then lay annother ruler at 90 degrees to the first ruler and a ruler at 45 degrees. I have used 200M radius in my example.

3. Lay annother peice of track at 90 degrees from the end of the second ruler and use the straighten track tool on it.

4. Now join the two peices of track by adding a third peice, all should be laid in the same direction. Do not put any joins in the third peice of track, go from the end of the first peice to the beginning of the second peice all in one movement.

5. Now go to the centre of the curve and insert one spline point where the track crosses the ruler.

6. Drag the new spline point outwards till it lines up with the end of the ruler.

That's all there is to it. you get a nice smooth curve at a predetermined radius.
Note the third ruler is always at half the total angle angle of the curve.
For smaller angle curves i.e. say ten or fifteen degrees you would want to use a much larger radius say about 5 or 6 hundred metres.

Hope this helps,
laying tangents first

I'm not aware of what's been posted outside of this thread, but I find it best to get a basemap or accurate to-scale diagram down. From there, I find it easiest to lay a couple of tangents by eye and measure the same distance along each one to find the required points for a constant radius curve. This youtube video demonstrates the process.

If you need to add intermediate points to aid with smoothness, you need to find the radius of the curve. If the curve is short, the radius tool in TRS should give you an accurate value, if not then this formula will (many thanks to my dad for working it out)


r is the radius of the curve
c is half of the chord of the circle formed by linking the two spline points already placed
t is the length from where the two tangents meet to where they meet the circle (To the spline points, in other words)

All we need now is an ACCURATE protractor for measuring. Last time I looked, the ones on the DLS look like they were good for nothing but show.
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Why go do all this trouble above, just paint a round ground cover that differentiates from the one already there with the right radius (which one can adjust till right) and place your track along its edge in equal distances. You can fine tune this by either shifting your spline points around or inserting any extra ones needed.

This gets me a nice round radius of my tracks anytime where and how I want them. Too easy :)

Come to think of it, I could also create some different templates as a scenery item which can be installed on the ground where needed. Around its edge the track could be build and the template can be deleted after creating the track. If someone could tell me some popular radii (radiuses to the uneducated ones :) ), I could whip some up in the next few days.


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I just posted about some track guides both straight and curved in the freeware forum, maybe they will be a help.
There are some curve templates avalable on the DLS. They are objects that are only visible in surveyor and allow track spline veritices to be locked onto points along them. But watch out - some sets use European curve designations.
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