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Re: NYC Minimum Curve Radius

Posted by Jeff H. on Sun Oct 2 00:23:29 2005, in response to Re: NYC Minimum Curve Radius, posted by JayZeeBMT on Sat Oct 1 07:40:57 2005.

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Curves can be measured either in terms of radius or "degree".
The latter method refers to how many degrees are turned when
traversing 100 feet of the curve. For up to moderate curves of
about 20 degrees, the formula R=5730/D, where R is the radius and
D is the degree of curvature, is reasonably accurate. For sharper
curves commonly encountered in transit or street railway work,
specifying the radius is more accurate.

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Re: NYC Minimum Curve Radius

Posted by stephenk on Sun Oct 2 04:25:41 2005, in response to Re: NYC Minimum Curve Radius, posted by Broadway Lion on Sat Oct 1 22:50:33 2005.

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"Sorry, this is a *real* railroad, not HO scale.

Curves are measured in degrees, not radius."

Must be a North American thing, as over here in Europe, we use the radius.



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Re: NYC Minimum Curve Radius QUIZ - Answer

Posted by Rail Blue on Sun Oct 2 07:28:10 2005, in response to NYC Minimum Curve Radius QUIZ - Answer, posted by Train Dude on Sat Oct 1 21:44:03 2005.

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Thanks! Very interesting.

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Re: NYC Minimum Curve Radius

Posted by Train Dude on Sun Oct 2 11:03:33 2005, in response to Re: NYC Minimum Curve Radius, posted by Broadway Lion on Sat Oct 1 22:50:33 2005.

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Sorry but you are incorrect. Curves on NYCT are measured in both radius and angle. You might, for example, have a 15 degree curve on a 4 track mainline. All 4 tracks will curve 15 degrees but the radius will vary from teack to track.

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Re: NYC Minimum Curve Radius

Posted by Jeff H. on Mon Oct 3 03:22:15 2005, in response to Re: NYC Minimum Curve Radius, posted by Broadway Lion on Sat Oct 1 22:50:33 2005.

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Curves are measured in degrees, not radius.

Elsewhere in this thread, I explained how degree of curvature and radius of
curvature are different ways of expressing the same thing, and
the reasons why degree is more useful in mainline RR applications
where curves are slight, and radius is more often used in transit
and street railway applications.

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Re: NYC Minimum Curve Radius

Posted by Jeff H. on Mon Oct 3 03:24:56 2005, in response to Re: NYC Minimum Curve Radius, posted by Train Dude on Sun Oct 2 11:03:33 2005.

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You might, for example,
have a 15 degree curve on a 4 track mainline. All 4 tracks will curve 15 degrees but the radius will vary from
teack to track.


That is not what most railway engineers would understand to be
the meaning when you say "15 degree curve". What you are really
talking about is a curve with "15 degrees of included angle"
or "15 degrees total angle".

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Re: NYC Minimum Curve Radius

Posted by RonInBayside on Mon Oct 3 08:41:11 2005, in response to Re: NYC Minimum Curve Radius, posted by Jeff H. on Mon Oct 3 03:22:15 2005.

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Basically, it's looking at the same basic principle from 2 different perspectives 90 degrees apart (or should I use a radius to express that 8-) )

Great explanations. I learned a lot. Thank you.

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Re: NYC Minimum Curve Radius

Posted by Wayne-MrSlantR40 on Mon Oct 3 23:29:33 2005, in response to Re: NYC Minimum Curve Radius, posted by Bronx Danny on Sat Oct 1 08:38:04 2005.

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Technically the #7 south of Queensboro Plaza is single tracked in effect because the two tracks are one above the other. For a multi-tracked RoW - likely #2/#3 west of Park Place could be the sharpest.

wayne

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Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by Ed Alfonsin on Tue Oct 4 00:23:08 2005, in response to NYC Minimum Curve Radius, posted by stephenk on Fri Sep 30 20:22:58 2005.

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I may have missed it, but what do the various radii convert to for model use to be prototypical? I'd be interested in O, HO, maybe N and G as well.

The MTH R-1 specs say that it should be used on minimum 42" diameter track. What would that convert to in the 12" to the foot world?

Thanks much,

Ed Alfonsin

(trained as a medievalist, when we didn't have the zero)

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Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by Jeff H. on Tue Oct 4 02:01:38 2005, in response to Modeling Curves (Was: Re: NYC Minimum Curve Radius, posted by Ed Alfonsin on Tue Oct 4 00:23:08 2005.

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Model RR equipment often has curves that would be unrealistically
tight if scaled out. This is especially true of 3-rail O scale.
Go to the nmra web site to learn more about scales and radii.

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Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by BIE on Tue Oct 4 05:36:47 2005, in response to Modeling Curves (Was: Re: NYC Minimum Curve Radius, posted by Ed Alfonsin on Tue Oct 4 00:23:08 2005.

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42"/12=3.5 feet x 48 (Scale Ratio) =168 feet (circle diameter)/2=84feet (Prototype radius of "O42" Track)

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Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by Steve B-8AVEXP on Tue Oct 4 14:17:54 2005, in response to Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius, posted by Jeff H. on Tue Oct 4 02:01:38 2005.

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A. C. Gilbert's Pike Master track, introduced when the company started its downward spiral, has extremely tight curves. A 4-8-4 American Flyer Northern for example cannot negotiate the curve while the earlier GP-7 trucks won't swing out far enough because of the long end steps. These steps had to be shortened later. The front coupler had to be removed from Alco PA units as well. The track looked realistic, but was cheaply made.

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Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by Ed Alfonsin on Tue Oct 4 14:18:08 2005, in response to Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius, posted by BIE on Tue Oct 4 05:36:47 2005.

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Thanks.

It looks like O-42 track would represent sharp curves for ordinary railroads, but would be reasonable for model subway trains and maybe even for yards and stations where longer commuter or regular passenger cars would be operating at slow speeds.

Ed Alfonsin
Potsdam, New York

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Re: NYC Minimum Curve Radius

Posted by R36 #9346 on Tue Oct 4 15:41:55 2005, in response to Re: NYC Minimum Curve Radius, posted by AcelaExpress2005 on Sat Oct 1 10:57:19 2005.

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Tighter than City Hall loop.

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Re: NYC Minimum Curve Radius

Posted by R36 #9346 on Tue Oct 4 15:56:53 2005, in response to Re: NYC Minimum Curve Radius, posted by Wayne-MrSlantR40 on Fri Sep 30 21:37:14 2005.

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I'll look through my data and come up with a comprehensive list of these curves and their radii. I'm pretty sure that the tightest is on the Manhattan-bound J line just outside Crescent Street.

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Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius

Posted by Jeff H. on Wed Oct 5 00:08:09 2005, in response to Re: Modeling Curves (Was: Re: NYC Minimum Curve Radius, posted by Ed Alfonsin on Tue Oct 4 14:18:08 2005.

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IF it scales to 84' radius, then it is tighter than anything
on the NYC subway system.

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NYC Minimum Curve Radius--That table I promised you.

Posted by R36 #9346 on Wed Oct 5 16:20:35 2005, in response to Re: NYC Minimum Curve Radius, posted by Wayne-MrSlantR40 on Fri Sep 30 21:37:14 2005.

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Here's that table I mentioned earlier. Please note that I have only considered IRT and BMT lines in this table, since my data for the IND lines does not show curve radii.

CurveRadius (Ft) 
City Hall Loop147.25 
East of Crescent St147.5CL
D4 at portal north of 36 St/4 Av165 
South Ferry Station (inner)178 
West Farms Junction (North of E. Tremont)180 
North of Park Place190 
149 St Loop190 
South Ferry Station (outer)191 
North of Fulton St/William St195 
West of Marcy Av197 
South of Queensboro Plaza200 
North and South of Grand Central (4)(5)(6)200 
West of Cypress Hills200CL
North of Fulton St/Broadway200 
Malbone St (O1-264)200 
South of 45 Rd Station215 
Southbound N north of Queensboro Plaza218 
North of Simpson Street240 
Malbone St (O1-261)240 
South of Wall/William250 
South of Graham Avenue254CL
South of Clark Street272 
Compass-North of Wyckoff Av275CL
Northbound 1 north of Times Sq276 
North of Saratoga Av286 
West of Bowery295CL
South of E. 180 St300 
North of 9th Avenue/West End300CL
North of Brighton Beach300CL


CL indicates that a non-track centerline of survey was used to determine this radius. This means that the inside track of curves so marked has a radius smaller than that shown.


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Re: NYC Minimum Curve Radius--That table I promised you.

Posted by stephenk on Wed Oct 5 17:38:58 2005, in response to NYC Minimum Curve Radius--That table I promised you., posted by R36 #9346 on Wed Oct 5 16:20:35 2005.

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Very interesting, thanks!

Just for comparison, some approx London Underground minimum curve radii

Caxton Curve (Central) 200ft/66m (16mph)
Kennington Loop (Northern) 75m (15mph)
South Kensington, Holborn (Piccadilly) 600ft/100m (20mph)
Various curves at locations on Bakerloo 600ft/100m (20mph)



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Re: NYC Minimum Curve Radius--That table I promised you.

Posted by Wayne-MrSlantR40 on Wed Oct 5 19:30:43 2005, in response to NYC Minimum Curve Radius--That table I promised you., posted by R36 #9346 on Wed Oct 5 16:20:35 2005.

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Thank you kindly, duly noted and recorded.

It's my guesstimate based on the above that NO IND curve, not even those at 90 degrees, have a radius less than 300 feet. The sharpest one I've been able to suss out is on the A/C between Chambers and Bway-Nassau.

Once again, thanks for the information.

wayne

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Re: NYC Minimum Curve Radius--That table I promised you.

Posted by EMSR7000 on Wed Oct 5 21:49:48 2005, in response to NYC Minimum Curve Radius--That table I promised you., posted by R36 #9346 on Wed Oct 5 16:20:35 2005.

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Hmmm...South Ferry inner and outer tracks vary by only 13 feet, and that with a row of columns in between. What's the normal track centers on former IRT tangent track - 12 feet?

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