# Switch Radius



## dslinick (Nov 7, 2018)

Every time I think that I understand track and switch radius, I find myself confused. Currently building my first steamer- Aster/Accucraft BR-5 and designing a simple loop in the back to run it. I got a bunch of very large radius Aristocraft track... 10 ft radius and I want to add a small siding with w switch. Aster specs a 2 meter minimum turn radius. Does that mean that only an LGB R5 or Aristocraft R6 (so much for standardization) will work?


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## armorsmith (Jun 1, 2008)

2 Meter is = 6.5 feet approximately


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## dslinick (Nov 7, 2018)

Understood, but still....will an LGB R3 22.5 deg switch be adequate for a loco that specs a 2meter min turn radius?


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## ferroequinologist (May 8, 2016)

Hi Dslinik, I assume the loco is the British 5MT 4-6-0 (a nice loco) my advice would be to stick to 10 foot Radius minimum or greater whatever the brand especially in turnouts for two reasons. 
Firstly while the loco could negotiate 6.5 foot radius it will not "be happy" as curve friction will drop running speed and pulling power on a live steamer like this where you have to put more throttle on for the curves and take it off for the straights. On a short track this can become tiresome even with radio control. Also on tight reverse curves, like negotiating left then right through two turnouts, can cause derailments as the wheels want to rise over the rail given half a chance especially on 'toy train spec' frogs of some brands. I have a few Aster 1/32 loco's than can run on 7 foot radius curves but they do not like it at all and often refuse to negotiate less than 8 foot radius turnouts.
The other reason is that with most 1/32 scale models the rolling stock usually does not negotiate tight curves well especially going from a turnout to another (reverse curve). So for this British model if you want correct passenger carriages they are quite long with extreme 'overhang' on tight curves the 'buffers' will move out away from each other and then often lock together causing derailments. If you only wanted 4 wheel freight wagons then this is not a big problem.
In my experience staying with 10 foot radius curves especially in turnouts will solve many potential running problems and you will have great running trains that not only look more realistic on wider curves but very enjoyable to run in steam and you can run visiting loco's and trains as well.
Russell


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## Gary Woolard (Jan 2, 2008)

I'm going to stick my oar in here, although that oar is shaped more like a question mark!

Let's assume the 10-foot radius to be safe (although in my experience with N.G. Accucraft, 8-foot radius has seemed adequate). I am as confused as dslinick, or more, about how to interpret the 
" R5" and "R6" nomenclature. I was looking at the dealer's room at the recent Portland N.S.S., and I couldn't find anything larger than an R6 in code 320. (Pete Comley at Sunset Valley seemed to have some wider switches, but all his stuff is code 250.)

Has anybody seen a table, or a data sheet, that actually answers that question?

Thanks,


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## Pete Thornton (Jan 2, 2008)

> will an LGB R3 22.5 deg switch be adequate for a loco that specs a 2meter min turn radius?


As you can see from the following (from the LGB website) the R5 is >2m (=2,000mm). R3 is just over 1m so the answer is no, it won't.


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## Pete Thornton (Jan 2, 2008)

> Has anybody seen a table, or a data sheet, that actually answers that question?


There are many threads on MLS and elsewhere that answer that question. Just google "lgb track radius" and do some reading.


To confuse things, Train-Li, who make switches, decided to simplify (!) things and use the radius in the name, so their R6 is 6' radius. You need an R7 for that 2m minimum.
And scale switches don't even use radius - they use the frog angle expressed as an incline ratio. So a #6 switch has a frog that diverges 1 unit for every 5 units. That's about a 9 1/2" radius. You need a #5.


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## krs (Feb 29, 2008)

Some general things to note:


As far as the "R" numbers are concerned, only R1 at 600 mm radius is the same for all manufacturers (afaik). The US manufacturers show R1 as 4 ft diameter curve, but in reality it's really 600mm
http://www.gbdb.info/details.php?image_id=6316


Second point is that US manufacturers use "diameter" to indicate the size, European ones use "radius" - people sometimes get that confused


And finally, the switch designation, ie #6 switch for instance that Pete mentioned above, is used only by US manufacturers, European manufacturers use the "R" designation of the radius of the curved section of the turnout, so an LGB R5 turnout for instance.


BTW, I never heard of an Aristocraft R6 curved track section. Not a designation Aristocraft themselves used. They always used the diameter in feet closest to the real diameter. Also keep in mind that Diameter and radius is measured centre-line to centre-line when it comes to track geometry.


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## armorsmith (Jun 1, 2008)

Pete, sorry to contradict you, but a #6 switch diverges 1 unit of width for every 6 units of run. A #8 is 1 unit of width for every 8 units of run, and so on.


Here is how the big boys do it https://www.wabtec.com/uploads/outlinedrawings/Turnout-Components-Section.pdf


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## Pete Thornton (Jan 2, 2008)

armorsmith said:


> Pete, sorry to contradict you, but a #6 switch diverges 1 unit of width for every 6 units of run. A #8 is 1 unit of width for every 8 units of run, and so on.
> 
> Here is how the big boys do it https://www.wabtec.com/uploads/outlinedrawings/Turnout-Components-Section.pdf


 Oops - sorry, typo.


Nice document - I saved it.


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## dslinick (Nov 7, 2018)

Thanks. I appreciate the detailed explanation. So either LGB R5 or Aristocraft R6 it shall be. (so much for standardization)


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## krs (Feb 29, 2008)

dslinick said:


> Thanks. I appreciate the detailed explanation. So either LGB R5 or Aristocraft R6 it shall be. (so much for standardization)



I asked this before - where do you see reference to an Aristocraft R6 switch?
There is no such thing.
There is an Aristocraft #6 switch, but as Pete explained, at least I think he did, that a #...switch designation relates to the angle of the frog expressed as a ratio of divergence of the rails at that point - that is how prototype turnouts are described in North-America.
The LGB R5 turnout designation relates to the radius of the curved section of the turnout which also relates to the way turnouts are designated in Central Europe.


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## Totalwrecker (Feb 26, 2009)

armorsmith said:


> Pete, sorry to contradict you, but a #6 switch diverges 1 unit of width for every 6 units of run. A #8 is 1 unit of width for every 8 units of run, and so on.
> 
> 
> Here is how the big boys do it https://www.wabtec.com/uploads/outlinedrawings/Turnout-Components-Section.pdf


Thank you, that is an excellent educational link.


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## armorsmith (Jun 1, 2008)

I do wish that people would speak in terms that the rest of the world understands. LGB's gibberish of R1, R3, etc. means nothing to the rest of the world that is not part of the Red Box Brigade. Please use either Radius or Diameter when discussing circles of track.


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## Chris Scott (Jan 2, 2008)

dslinick:

You need a Swiss Army Knife of Model Railroading. Enter "Handy Converter" Below are screen captures of the Handy Converter "Large Scale Track." One shows data and dimensions for Aristocraft and the other for LGB. Look closely at the Manufacturing heading and the options available. Handy Converter literally has every bit of information you will ever want or need in Model Railroading.

You will love this tool. IT's available from Stan Silverman's web site:
www.StansTrains.com

Anyone here who has and has used this tool will confirm what I've written

All the best.


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## krs (Feb 29, 2008)

armorsmith said:


> I do wish that people would speak in terms that the rest of the world understands. LGB's gibberish of R1, R3, etc. means nothing to the rest of the world that is not part of the Red Box Brigade. Please use either Radius or Diameter when discussing circles of track.



Ironically it was actually the US market that drove LGB to come up with these "R" designators.
If you look at the early LGB catalogs, from 1968 to 1981, the curved track is defined by the diameter. 120, 155 and 235 cm in the 1981 catalog.
Al Lenz started the US LGB club in late 1977, with less than a dozen people; by the early 80's LGB sales in the US started to boom and the R1, R2 and R3 designators were introduced to simplify any discussion about LGB curved track sections in the US.
The confusion only arose when Piko introduced their track system around 2007 and for some reason (which I would love to understand), they used the R1, R3 and R5 designators, where R1 has a radius of 600 mm, same as LGB, but R3 has a radius of 921.54 mm and R5 a radius of 1243.04.
So Piko R5 curved track is just a little bit bigger than LGB R3 curved track at 1175 mm.


The other thing to note is even though Aristocraft and other North-American manufacturers show their curved track as 4 ft diamer, 8 ft diameter etc., not a single of the 12 different curved track section that Aristocraft offered was actually exactly that diameter.


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## krs (Feb 29, 2008)

Chris Scott said:


> dslinick:
> 
> You need a Swiss Army Knife of Model Railroading. Enter "Handy Converter" Below are screen captures of the Handy Converter "Large Scale Track." One shows data and dimensions for Aristocraft and the other for LGB. Look closely at the Manufacturing heading and the options available. Handy Converter literally has every bit of information you will ever want or need in Model Railroading.
> 
> ...


There is an extra "d" in the url, it should be
https://stanstrains.com/


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## Chris Scott (Jan 2, 2008)

krs said:


> There is an extra "d" in the url, it should be
> https://stanstrains.com/


Corrected. Thanks.


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## armorsmith (Jun 1, 2008)

krs said:


> Ironically it was actually the US market that drove LGB to come up with these "R" designators.
> If you look at the early LGB catalogs, from 1968 to 1981, the curved track is defined by the diameter. 120, 155 and 235 cm in the 1981 catalog.
> Al Lenz started the US LGB club in late 1977, with less than a dozen people; by the early 80's LGB sales in the US started to boom and the R1, R2 and R3 designators were introduced to simplify any discussion about LGB curved track sections in the US.
> The confusion only arose when Piko introduced their track system around 2007 and for some reason (which I would love to understand), they used the R1, R3 and R5 designators, where R1 has a radius of 600 mm, same as LGB, but R3 has a radius of 921.54 mm and R5 a radius of 1243.04.
> ...



All you have convinced me is that R numbers are gibberish, confusing, and non-productive. Clearly stating a radius/diameter in either Imperial (inches) or metric (millimeters) is clear as glass.


Here is a web site that has their stuff togehter. http://www.gbdb.info/details.php?image_id=6316&sessionid=ab908f5742ba73bf3e799bda251baad7&l=english


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## Chris Scott (Jan 2, 2008)

dslinick:


*This is another invaluable MRR & RR data website:*
http://www.urbaneagle.com/data/index.html









Website has more data than you will ever want or use, but when you want a piece of data you'll be really glad you know where you might find it. And then you won't know whether what you're looking for is there it's still aa place you'll always remember to check - at least that's how it has worked for me over 20 years.

*Sample of the website data Table of Contents:*


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## Chris Scott (Jan 2, 2008)

krs said:


> Ironically it was actually the US market that drove LGB to come up with these "R" designators.
> If you look at the early LGB catalogs, from 1968 to 1981, the curved track is defined by the diameter. 120, 155 and 235 cm in the 1981 catalog.
> Al Lenz started the US LGB club in late 1977, with less than a dozen people; by the early 80's LGB sales in the US started to boom and the R1, R2 and R3 designators were introduced to simplify any discussion about LGB curved track sections in the US.
> The confusion only arose when Piko introduced their track system around 2007 and for some reason (which I would love to understand), they used the R1, R3 and R5 designators, where R1 has a radius of 600 mm, same as LGB, but R3 has a radius of 921.54 mm and R5 a radius of 1243.04.
> ...



All this is why and an excellent reason to use only FLEX track, from any manufacturer, rather than go anywhere near sectional track. And use only turnouts, mistakenly called switches, that are spec'd in "degrees (of curvature)" and use the Handy Converter to translate degrees to "radius."

Ultimately the only way to know if sectional track of X Radius or Turnout X Radius works successfully (fits) a particular real radius (your) layout is to build your layout and see if it WORKS (sectional track or specific turnout) as advertised. 

If you one day move beyond the world of defined radius sectional track and turnouts you will encounter a new world of having to use Flex tract and bend your curves and either build your own turnouts or buy turnouts designated as; #3, #4, #5, #6, #8, #10. When you get there the fun begins again, "what is?" You'll still come back to the same principle, "Ultimately the only way to know if a Turnout X Radius works successfully (fits) a particular real radius on (your) layout is to build your layout and see if it WORKS."

Word to the wise, everyone told me a #8 turnout was for 15' radius curves. So I bought a fairly large number of #8 turnouts. That was a total failure. I had to return, with quite some difficulty, most of the #8 turnouts exchanging them for #10 turnouts. Probably should have bought one turnout and tried it, but I didn't so a valuable lesson was had. Luckily I was going to have to spend more money for #10 turnouts so the thought of more money in my dealers pocket was good persuasion. 



$0.02 Best of luck.


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## armorsmith (Jun 1, 2008)

Chris,


I agree that Urban Eagle has some great information, however please understand that there is a caveat - there are several broken links, for starters the link to Stan's site. Your link is correct, Urban Eagle's needs to be updated. Sometimes they are the one I am looking for. Also, some of the material presented is dated and may or may not agree with current practices. An example is the letter scale for 1:29. Urban Eagle lists this as 'A'. NMRA Standard S-1.2 Standards for Scale Models has no such scale listed.



As to your comment about using flex track, that also has a caveat. First, you are assuming that the reader either owns or has access to, a high quality dual rail bender. Some clubs own one that they loan or the individual may know someone who owns one. Second, you are making the assumption that the user knows where he is trying to go. Based on the OP, it is my interpretation that the OP was not sure. He was searching for information on what his locomotive was capable of, or what is the minimum track curvature the locomotive can function on. What was attempted was to provide numbers the OP could understand and follow.


Referencing your comments on Aristo Craft track not being 'exactly what was stated', absolutely. Neither is USAT or Bachmann or any other track manufactured in China. It is all to Metric dimensions, and converted (rounded) to the nearest Imperial number. The result of moving our manufacturing overseas.


So, lets use real dimensions - regardless of rounded Imperial, exact Imperial or Metric. No more gibberish R this or that.


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## on30gn15 (May 23, 2009)

Scanning through the thread I didn't see this said:
Looking up the locomotive's absolute minimum radius and then building your layout with that as your standard radius is essentially guaranteeing nothing but trouble when running your trains.


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## Greg Elmassian (Jan 3, 2008)

dslinick said:


> Every time I think that I understand track and switch radius, I find myself confused. Currently building my first steamer- Aster/Accucraft BR-5 and designing a simple loop in the back to run it. I got a bunch of very large radius Aristocraft track... 10 ft radius and I want to add a small siding with w switch. Aster specs a 2 meter minimum turn radius. Does that mean that only an LGB R5 or Aristocraft R6 (so much for standardization) will work?



I've been watching this thread and while there is a lot of wisdom, there's what appears to be some misdirection.


Taking the OP's post above, he is looking for a loop with a switch. 



The loop part is simple, right, so Aster specs 2 meter (slightly over 6.5 feet) so, his choice to use 10 foot radius is great, a comfortable margin over the minimum radius. End of discussion there, he's doing well, and not trying to go to the tightest curve.


The other part seems to have thrown everyone off scent. if you want to make a siding, it's NOT just about the curvature of the switch, but you also need to ask if the track on the siding continues tangent (straight) from the switch, but if it follows normal practice and bends back parallel to the "main line".


If this is true, you wind up creating an "S" curve right past the switch where it's basically much "tighter" than the switch alone. Maybe the OP can come back and comment here, and thus get a better answer.


Finally, with locomotives that need broader curves, I find it is much easier to look at the frog number (diverging angle) to compare switches. It's not perfect, but it the frog number that really controls the "tightness" of the "curve" through the switch.


And in this scale, looking at anything less than a #6 frog is probably foolish, if you really want the loco to enter and leave trouble free.


There are places where people have determined the frog number for LGB and Piko and other "R type" switches, but in general I would not recommend any of thes switches in this case.


Best, Greg


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