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Main line on the diverging route of a turnout?

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Main line on the diverging route of a turnout?
Posted by JimInMichigan on Thursday, September 22, 2016 5:48 PM

Is it proto in any way to have the main line follow the diverging route of a turnout?

Also, do model trains run ok by doing so?

I'm running 6 axle HO scale. Turnout is a #8.

Photo example:

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Posted by floridaflyer on Thursday, September 22, 2016 6:10 PM

I have one #6 in the same configuration. Haven't had a problem in 9 years

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Posted by Bob Schuknecht on Thursday, September 22, 2016 6:25 PM

I don't know how prototypical it is, but my main line uses the diverging route of a turnout at the east end of my passing siding. The main is the thru route at the west end of the siding. 

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Posted by selector on Thursday, September 22, 2016 6:31 PM

Jim, if the prototype can avoid doing so, they prefer to diverge off the main and to let the main be the through route.  I suspect it's somewhat less prone to derailments statistically, particularly at track speed.  However, I did what you propose in two places on one of my layouts because I had the track geometry that favoured it. I used hand-laid #8 of the Fast Tracks type.  They worked really well. If you gotta, you gotta.

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Posted by peahrens on Thursday, September 22, 2016 6:35 PM

I imagine one might find various prototype arrangements but Im no authority.

I'd say if your turnout "turn" is of a similar or greater radius than your mainline curves, why not set it up that way if that arrangement makes sense.  From NMRA RP-12.9 (HO scale) the listed curve ("curved rail radius") within the turnout for numbers 4, 5, 6, 7 and 8 are (to nearest inch) 15, 25, 38, 49 and 66" radius, respectively.  So your 6-axle diesels should do fine on #5 or greater. 

Paul

Modeling HO with a transition era UP bent

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Posted by xdford on Thursday, September 22, 2016 6:35 PM

Hello Jim,

I can think of several examples here in Australia where a mainline takes a diverging turn... also a couple of areas where both lines are part of a Wye  turnout so go right ahead. My own layout is a 4x8 and I run an F45 with no problem around the curves  and my turnouts are the Peco small radius (around #4's) and after all... it is your railroad!

Cheers from Oz

Trevor

 

 

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Posted by NVSRR on Thursday, September 22, 2016 7:32 PM

Yes it is common for such a practice.  There are countless examples.  So have at it.

A pessimist sees a dark tunnel

An optimist sees the light at the end of the tunnel

A realist sees a frieght train

An engineer sees three idiots standing on the tracks stairing blankly in space

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Posted by BroadwayLion on Friday, September 23, 2016 10:58 AM

This is a common thing to see, BUT...

While you may call it the Main line as far as the track plant is concerned, it IS the diverging route. You can take the tangent route at speed any time you like, but the siverging speed is controled by the frog. (ribit ribit) The formula (rule of thumb) is 2 x the turn out number. A number 8 turnout has a 16 mph speed limit. A number 20 turnout has a 40 mph speed limit.

Anything faster than that requires movable frog points as well as movable switch points.

While on our model railroads, this probably does not bother a hill of beans. We have to make do with many liberties. NYCT has many locations such as you describe, but then the speed limits are as I have described them.

ROAR

The Route of the Broadway Lion The Largest Subway Layout in North Dakota.

Here there be cats.                                LIONS with CAMERAS

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Posted by carl425 on Friday, September 23, 2016 3:13 PM

I think the model railroad faux pas you are thinking about is the case where an industrial spur is on the through side of the turnout.  My belief is that this is not a prototypical practice although it is often very convenient for modelers.

What you have however with your route to staging is more like a case of a diverging main line, which would be a very common prototype practice.

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Posted by ckape on Friday, September 23, 2016 6:01 PM

In most cases, the route to staging would also be considered a mainline, and then you can't get away from having one of the mains taking the diverging route.

Even if that doesn't apply, prototype railroads also have to make compromises for space constraints, although usually not as often as model railroads do.

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Posted by NittanyLion on Saturday, September 24, 2016 12:24 AM

Think about how many junctions out there would have to route traffic through what is basically the diverging route.  Right outside my office, at CP Virginia in DC, Amtrak and VRE break off from the CSX main to head north to Union Station.  Technically, not a main, but it sees as much traffic as almost any main in the country.  Goes through the diverging route of a turnout.

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Posted by tomikawaTT on Saturday, September 24, 2016 1:59 PM

I recall reading about such a situation in Texas a few years back.  In a nutshell, the route south was straight, while the more heavily traveled east-west route took the diverging side of the turnout and suffered the speed limit problems mentioned.  The company reconfigured the right hand turnout into a left-hand, put the straight side on the preferred route and let the lesser number of southbound trains suffer the speed restriction while the westbounds could now blast through at track speed.

Of course, we model rails don't have the luxury of wide open spaces.  That little realignment probably involved a piece of territory as big as my main station between home signals.

My thought is that having the major route diverging isn't bad as long as the straight route leads to something more significant than a weed-grown spur.

Chuck (Modeling Central Japan in September, 1964)

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Posted by BroadwayLion on Saturday, September 24, 2016 2:29 PM

tomikawaTT
My thought is that having the major route diverging isn't bad as long as the straight route leads to something more significant than a weed-grown spur.

 

Even thata can be prototypical.

On previous layout of LION the tangent track was the siding, and the curved track went over a bridge into the town of Fornost.

The story wat that this tangent line was to go further north but the need for it never developed and the mountains proved to be onoerous. If it were easier, the railroad would undoubtedly have pushed on expecting development to follow. As it was, that never happened.

On NYST the tanget track heads right into a concrete wall... nothing was built beyoond it, but insted the line curves to the north to Follow Broadway. When the bridge line was built there was still a question as to if it would be awarded to the IRT or to the BMT. It went to the BMT and so it turned up broadway, had the line been assigned to the IRT, it would have continued forward to join the 7th Avenue Line.

When the BMT was awarded the bridge route, the Flatbush Avenue Extention was created so that the subway could run under it to the bridge, otherwise all BMT Fourth Avenue traffic would have been via the Tunnel.

 This also explains why the DeKalb Avenue station has six tracks. When built it was supposed to be a local stop on the 4th Avenue line before it turned west to enter the Tunnel. When the BMT got the route, they extended the Brighton Line (originally it went across Franklin Avenue tho the Fulton Street elevated) making the side platforms into island platforms. Thur 4th Avenue Express trains Skip Dekalb, While the local, now on the alignment that would have been an express alignment in other stations ducked under the rest of the tracks to head west through the tunnel, and the Brighton tracks (now an express service) came in along the wall where one would otherwise expect to find a local train.

Interesting, isn't it? You have to make up interesting stories to compliment the geography of your railroad.

 

ROAR

The Route of the Broadway Lion The Largest Subway Layout in North Dakota.

Here there be cats.                                LIONS with CAMERAS

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