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Author Topic: Prototype Minimum Radius Equivalent in N Scale?  (Read 3691 times)

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Kisatchie

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Prototype Minimum Radius Equivalent in N Scale?
« on: January 08, 2014, 05:38:08 PM »
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What is the (more or less) minimum radius for prototype railroad mainlines, and what does that equal in N scale? I'm finally working on a track plan for my dream layout, and I want to see how far off I'll be.


Hmm... my guess is, way
off...

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ryan_wilkerson

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #1 on: January 08, 2014, 05:43:49 PM »
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Just as a ballpark estimate...Cantara Loop near Dunsmuir, CA is about 800 feet in diameter. In N that would be 5 feet or 60 inches in diameter. So a 30" radius is what I'm using. I read somewhere that Cantara is the sharpest mainline curvature in California so most mainlines are broader than that.
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garethashenden

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #2 on: January 08, 2014, 05:59:31 PM »
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Prototype curves tend to be measured in degrees instead of radius. This website may be helpful: http://www.steamlocomotive.com/model/curve.shtml
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Kisatchie

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #3 on: January 08, 2014, 06:24:27 PM »
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Quote from: garethashenden on January 08, 2014, 05:59:31 PM
Prototype curves tend to be measured in degrees instead of radius. This website may be helpful: http://www.steamlocomotive.com/model/curve.shtml

Ahhhhhh, trigonometry, ahhhhhh...


Hmm... I prefer termite-
ology...

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ryan_wilkerson

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #4 on: January 08, 2014, 06:27:59 PM »
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Quote from: garethashenden on January 08, 2014, 05:59:31 PM
Prototype curves tend to be measured in degrees instead of radius. This website may be helpful: http://www.steamlocomotive.com/model/curve.shtml

Thanks for that link. Cantara Loop is listed as 14 degrees.
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GimpLizard

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #5 on: January 08, 2014, 06:44:20 PM »
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Quote from: garethashenden on January 08, 2014, 05:59:31 PM
Prototype curves tend to be measured in degrees instead of radius. This website may be helpful: http://www.steamlocomotive.com/model/curve.shtml

Trigomometry... cool!  :P
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ednadolski

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #6 on: January 08, 2014, 07:21:18 PM »
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Tehachapi Loop was built with 10-degree curves, which works out to 43" radius in N scale (79" radius in HO, FWIW).   So a scale model of the Loop in N would be over 7' in diameter.  (Very tempting, but I simply do not have the space :D)

BTW, 10 degrees is considered pretty sharp for the prototype.

Ed
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ednadolski

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #7 on: January 08, 2014, 07:27:35 PM »
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SDSONS has a conversion chart  (no trig required!):  http://www.urbaneagle.com/data/deg-curve.txt

Ed
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ryan_wilkerson

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #8 on: January 08, 2014, 08:03:30 PM »
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Quote from: ednadolski on January 08, 2014, 07:27:35 PM
SDSONS has a conversion chart  (no trig required!):  http://www.urbaneagle.com/data/deg-curve.txt

Ed

Nice, even better.
My 30" radius was very close!

Degree:     14.0
Proto Rad (ft): 410.28
N scale Rad (in): 30.77

I think WIlliams Loop in the Feather River Canyon is also pretty tight. Looks like about 1300 diameter from google maps.
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Kisatchie

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #9 on: January 08, 2014, 08:13:47 PM »
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Quote from: ednadolski on January 08, 2014, 07:27:35 PM
SDSONS has a conversion chart  (no trig required!):  http://www.urbaneagle.com/data/deg-curve.txt

Thanks! I bookmarked the site.


Hmm... what's on TV
tonight...?

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Two scientists create a teleportation ray, and they try it out on a cricket. They put the cricket on one of the two teleportation pads in the room, and they turn the ray on.
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jagged ben

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #10 on: January 08, 2014, 08:27:50 PM »
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The Cantara Loop is probably one of the tightest on a Class 1 mainline.  It's worth mentioning that that location had one of the worst string-lining accidents in railroad history.

Another way to chew on the question is to look at the datasheet for something like the MultiMax Autorack.
http://www.gbrx.com/files/files/NAR/Multi_Max/Multi_Max.pdf

"Curve Negotiability Radius"
...
"Coupled to 40’ Base Car: 345'"

(That translates to 25.5" in N scale). 

That sort of thing is going to set an absolute minimum for any general use track on a Class 1.  The only tracks that could be tighter would be industrial spurs that have rules that do NOT allow autoracks or similar length cars.   Mainlines, especially those on grades, have to be considerably above it due to string-lining concerns with long or heavy trains. 
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Chris333

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #11 on: January 08, 2014, 09:48:10 PM »
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I know you say mainline, but the freight terminals in NYC had tons of 50' radius curves. And in all the maps I've seen they are measured in radius not degrees  :P
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jmlaboda

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #12 on: January 08, 2014, 10:04:21 PM »
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There was one passenger terminal that the Kansas City Southern ran out of that had a 150' radius leading to it.  All of the KCS cars were able to negotiate it but had to do so close to a crawl.
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brokemoto

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #13 on: January 08, 2014, 11:38:00 PM »
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Quote from: Chris333 on January 08, 2014, 09:48:10 PM
I know you say mainline, but the freight terminals in NYC had tons of 50' radius curves. And in all the maps I've seen they are measured in radius not degrees  :P

If you look at the locomotive specification charts/sheets for NYCS, they do state 'locomotive designed to operate on ________radius curve.'
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Chris333

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Re: Prototype Minimum Radius Equivalent in N Scale?
« Reply #14 on: January 09, 2014, 12:18:03 AM »
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Quote from: brokemoto on January 08, 2014, 11:38:00 PM
If you look at the locomotive specification charts/sheets for NYCS, they do state 'locomotive designed to operate on ________radius curve.'
Now that you mention it, so do Erie loco sheets.
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