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Measuring curved track radius.

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  • Member since
    May 2009
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Measuring curved track radius.
Posted by allen93644 on Tuesday, May 19, 2009 8:23 PM

I hope this is not to dumb a question for you guys. I am a complete novice to Garden Railroading and want to try building some of my layout with earth and stone before laying track. My question is about using curved track. I am not ready to bend my own curves yet so I am going to bite the bullet and buy sectional curved track. The question is how is curved track measured? Is the raidus measured from the inside track, the outside track or in between the tracks? This might be answered somewhere but I could not find it. My prior layout experence was with "N" scale But I can't see that any more so I am giving a shot at this large stuff, at least if my wallet dosn't explode first. Thanks for any input.

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Posted by ttrigg on Tuesday, May 19, 2009 8:49 PM

The answer to your question is "all of the above" (depending upon brand name), at least from what I have experienced. There is also the factor that most rails are produced in "Metric" countries, and they slap a label of the nearest inch/foot size on it. Depending upon the manufacturer, a four-foot radius can come in somewhere between 46.5 and 49.5 inches.

I am a firm believer in bending my own rails. There are several advantages to rail bending. 1) Bend the size curve you need, not stuck with the 2, 3, or 4 curvatures the vendor produces. 2) Fewer rail joints make for fewer possibilities of the wheels "picking" a slightly off joint and derailing. 3) Reduced need for "feeder wires" if running track power. When I started out, I too, filled the back of the truck with sectional curves and straights which now fill boxes in the shed until such time as I need a quick siding realignment or such.

If you do go ahead with sectional, I would advise purchase the rails and build the subroadbed to fit. If you build the subroadbed first, then sectional may not fit. In that case get one complete circle of each size you intend to use and use it as a template while building the right of way.

Tom Trigg

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Posted by Independent Operator on Wednesday, May 20, 2009 12:25 AM

allen93644

I hope this is not to dumb a question for you guys. I am a complete novice to Garden Railroading and want to try building some of my layout with earth and stone before laying track. My question is about using curved track. I am not ready to bend my own curves yet so I am going to bite the bullet and buy sectional curved track. The question is how is curved track measured? Is the raidus measured from the inside track, the outside track or in between the tracks? This might be answered somewhere but I could not find it. My prior layout experence was with "N" scale But I can't see that any more so I am giving a shot at this large stuff, at least if my wallet dosn't explode first. Thanks for any input.

 I had problems with this when I first got into Backyard Railroading.  My major problem was that I ignored the question.  I bought some engines thagt would not make the turns on my backyard railroad because of it's four foot diameter curves.  Thats what a circle of track put together would measure to in diameter.  LGB starter sets had four foot diameter curves.  I had to build another layout in the sideyard to accomodate those engines and it works fine as it has curved track that has eight foot diameter curves.  I have seen a scale on some of the web sites that reference the curved track with R numbers for the curves that ties into what the diameter is.  WWW.onlytrains.com has that scale online I beleive.

RUDY JAGER, CEO OF THE LONE WOLF RAILROAD 

TRUST ME--I USED TO WORK FOR THE GOVERNMENT!

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Posted by gbbari on Monday, June 1, 2009 8:16 PM
Allen - Aristo-craft uses the centerline (between the rails) for their curved track radius dimension. You can see all of their track dimensions in their online catalog on their website (the catalog is a PDF document). Since their ties are 3 1/2 inches wide, you can then add half of that to the centerline to calculate the outer arc, and subtract 1 3/4 in. to calculate the inner arc.

LGB track is built to metric dimensions, but they also are centerline dimensions. They also have ties that are 3 1/2 inches across. Their current catalog (2008/2009) shows on p.119 the four sectional curved track diameters - both centerline and outer edge dimensions as measured across a full circle of each radius.

LGB R1= 1200mm diameter centerline, or 1286mm dia (outer edge of the ties)

LGB R2= 1560mm dia centerline, or 1646mm dia outer edge

LGB R3= 2390mm dia centerline, or 2476mm dia outer edge

LGB R5= 4640mm dia centerline, or 4726mm dia outer edge

I'm not sure. but it appears that USA Trains' sectional curved track is also measured using the centerline.

Hope that helps

Al

  • Member since
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  • From: Shire Counties UK
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Posted by two tone on Friday, June 5, 2009 11:02 AM

Hi Welcome to a great hobby,     I use R3 curves that gives me 8 feet diamiter any loco that is g gauge IE 2-6-0   2-8-0 wil run with no problems.  Also make sure your switches are the same.   Hope this helpsBow

                Age is only a state of mind, keep the mind active and enjoy life

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Posted by g. gage on Saturday, June 6, 2009 1:02 AM

Howdy Allen, welcome aboard; answering your question has been troubling me for sometime. Theoretically track is measured from the centerline. However consider that most of it is manufactured in countries using the metric system. Then we put it together with gaps and those gaps readjust with heat expansion and cold contraction. The world is not static, I live in California, believe me everything moves. Also the tighter the curve the more overhang on rolling stock, both outside and inside of curves, not to speak of rolling stock limitations. Most equipment will run on 8’ dia curves, however my longest piece of equipment (Aristo RDC) has a 3 ¾” overhang on each side. I use 10’ minimum up to 20’ where possible it’s much better looking. I would allow liberal track clearance.

 

I hope this helps, Rob

 

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