# Track Radius



## daveroesler (Jul 25, 2009)

New guy question: How is track radius measured? Is it to the mid point between the two rails? Or between one of the rails (inside or outside)?


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## Gary Armitstead (Jan 2, 2008)

Track in the large scale hobby, is measured in both radius AND diameter. Because I was a tool and die maker, I always measure as radius to the CENTER of the track section between the two rails. Somebody will jump in here with a different answer I'm sure.


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## rreiffer (Jan 14, 2009)

I suspect that in the end the final "fine tuning" of the radius as measured really does not make an impact, in fact if it does I can tell you now that your radius is too small!









I would attempt to build as large of radius as you have space and can afford. 

Rich


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## Greg Elmassian (Jan 3, 2008)

I've always used the centerline, most of the track planning software, and manufacturer's diagrams seem to do this also. 

Regards, Greg


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## RimfireJim (Mar 25, 2009)

I'm with Gary & Greg - centerline is the only logical reference for me. And I'm a radius guy, not diameter. (Does that make me less than well-rounded?







)
You might want to read this thread, where there's some discussion of stated dimensions versus actual dimensions for certain brands of track: track lengths and radii


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## Randy Stone (Jan 2, 2008)

Radius or Diameter? 

It really makes little difference which is used so long as it is used correctly. 

2 ft radius equals 4 ft dia. and so on. 

The problem occurs when someone says they have 4 ft diameter curves when they actually have 4 ft radius curves or vise versus. 

But to your question, the measurement is to the center of the two rails on a paticular section of track. So if you have a circle of track made of 2 ft radius / 4 ft dia curve sections, you can expect the distance from outside tie to out side tie accross the center of the circle being approx 51 1/2 inches. This means you cannot put a 2ft radius / 4 ft dia circle on a 4' x 8' sheet of plywood without the track hanging over the edge of the 4' side of the plywood. 

Hope this helps 

Randy


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## stanman (Jan 4, 2008)

I got the data for LGB track from Dave Buffington when he was representing LGB. It states that the measurements are "Center of track to center of track".


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## Voyageur (Oct 31, 2011)

Question from a novice : I have laid out all of the straight stretches in my garden so that I have the largest radius possible when I change direction. Is there a Garden Rail formula or method for determining the exact radius I will have at each turn ?


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## chuck n (Jan 2, 2008)

Voyageur:


What are the overall dimensions of the space you are planning to use: 10'x20', 8x40? Before you do any thing you need to know what space you have to use.


If you have one segment of track going west and the return track going east, measure the distance between the two segments of track and divide by 2. Another way would be to make a scale drawing of your space with your straight parts laid out on the drawing and start drawing arcs. A third way would be to take a piece of string and a stake. Pound the stake in where you think the center of your curve might, then measure the distance to the nearest straight piece of track. Measure the length of the string. Keep moving the stake until you are happy with the curve that you have. 


Some us have done it through trial and error, with what was commercially available at the time. At the time I built my current layout (1994) the largest radius of curve was the Aristo wide radius 5'. So I built it with 5' radius curves. I wasn't planning to get a rail bender and make my own curves. Had 10' radius been available then, I would have used it and I wish I had.




Chuck


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## Voyageur (Oct 31, 2011)

Thanks Chuck
#3 suggestion is so simple it escaped me.


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## Axel Tillmann (Jan 10, 2008)

Here is my opinion:

1. Coming from geometry and using a compass I only understand in my head radius







. So of course in discussions I only use radius because this give me a direct correlation to what it is. It's probably the same thing for me I can still visualize 1mm, 1cm, 1m... 0.25mm ..... but what is 1/8" of an inch









2. Very often I find missed opportunities in the garden layouts. becasue of the radius thinking poeple very often go from straight into a radius (regardless if they are using sectional track or straight track with a railbender). Nowhere in mother nature (prototype) do you actually see that they transition instantaneously into the radius curve, nor have I ever seen a curve with a constant radius. The transitioning "problem" can be potentially solved even with sectional by unscrewing the rails from the tie bed and then slightly applying pressure on a sectional rail piece until it straightens out on one end. Long term you train operations will thank you for that. Of course the more convenient way is bending you own track and make it as realistic as possible, and avoid curves with constant radius. It looks more natural.


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## VictorSpear (Oct 19, 2011)

I second this opinion. Time is well worth spent on planning easements and then transitions before laying track curves. For a good article on 'easing' into a 'transition' with some hints on anti-derailing :


http://www.trackplanning.com/easements.htm

I noticed the LGB track calculator provides the radius and angle but did not provide for the length of the arc. Knowing this length is useful if you are ordering flexible track for curves (like Flexgleis) and you have to 'Prepay on Ebay'

How much should I really order ($$$) if I know the planned radius and angle = (2 x Pi x Radius x Angle)/360 ...or use this link to get an idea: http://www.mathopenref.com/arclength.html 

* "Measure Thrice....Cut Once"*

Cheers
Victor.


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## Voyageur (Oct 31, 2011)

Victor and Axel - Thanks so much. I plan to construct my own rail bed so this business of easements and rail heights is very timely. 
I have saved the links and as a consequence will redraw the layout to ensure these issues are incorporated.


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## Gary Armitstead (Jan 2, 2008)

I use MasterCam software to layout my railroad. This software is not meant for this purpose. But I used it for so many years in manufacturing, I was just comfortable with it. But as Victor noted, it's nice to have the centerline to measure for buying lengths of flex track.


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## Voyageur (Oct 31, 2011)

Gary -- we have it too, so thanks for the prompt.


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