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- Thread starter eerbaugh
- Start date

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

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 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,

Bill69

can you email me those pics. they are too small to see on here.

No, just click on them. They link to the full size versions.

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.

Cheers

VinnyBarb

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.

Cheers

VinnyBarb

Last edited:

Lo_Poly hes right actully they stay small.

Lo_Poly hes right actully they stay small.

Not for me.

http://rail3dwiki.markhodson.nl/index.php?n=Tutorials.LayingNiceCurves

This tutorial is for a different game but works just as well for Trainz. Take a look.

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