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Jeff,

R1 is 2 foot radius, R2 2.5 foot radius, R3 is 4 foot, R4 ? R5 is about 7.5 foot radius. These are close but not exact. I'm sure some one will correct it.
 

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To add to what has been said, the R term is one that was used by LGB for their track radius measurements. R's 1,2 and 3 correspond pretty much to Aristocraft and USA track radius measurements but LGB actually measures in metric whereas Aristo/USA is measured in feet. Since this pretty much only applies to sectional track we only have to look at six or seven different curvatures. R1, R2 and R3 are the most common. It is also prudent to know that the wide radius turnouts from LGB have a different curvature than the ones from Aristo/USA.
 

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Note that Piko also uses "R1, etc., " but they are not the same as LGB's. As a rule, just forget about any cutesie nomenclature, and go by the actual measurements. Each manufacturer states what their curves are on their web site. Be careful to note whether the number is the radius or diameter, though. That varies depending on manufacturer.

Later,

K
 

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The 2 foot radius is not accurate as the LGB radius is really metric and is 600 mm which is a little less than 2 feet.

1200mm is about 47 and 1/4 inches.

Close for most, but when you get to larger measurements, you can be off over an inch.

PS the USA big switch is a real 3 feet (36 inches) long.
 

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Yep, Dan, you're absolutely correct about the metric part but how do you get "larger" measurements from a 2ft. radius curve? This is why we interchange R1 with 2ft. and R2 with 2.5 and so on. Note that I use the term "correspond" rather than saying they are the same. In my opinion, when talking about such a tight radius, any difference is so negligible as to be irrelevant. As we go larger though, the differences are magnified and then it does matter! :)
 

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Another point is that the radius measurement is to the track centerline... The R-1 (2 foot, 600m, or whatever you want to call it) WON'T fit on a 4' wide sheet of plywood.
 

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Searched for this but couldn't find it - what is the average minimum radius necessary for new cars and locos these days?

I have a whole bunch of 600mm track that I don't want to toss (I picture it being the scenic route, or something like that). But would I be considered safe with an 8 foot diameter? 10 foot?
 

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10' diameter (5' radius) is a good, solid minimum that will easily accommodate 95% of what's available today. You could go down to 8' diameter (4' radius) and run probably 70% of what's available, but the large stuff will look funny doing so. You can go smaller without too much difficulty, but you begin to limit yourself to what will run reliably over the track. Much of the new stuff--especially in the 1:20 realm--requires an 8' minimum diameter (4' radius).

Later,

K
 

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Also take note that AristoCraft track has similar dimensions as LGB track with a metric origin except the radius is marked on the box to the nearest foot size but is completely inaccurate information.

Andrew
 
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