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How is the radius of Atlas sectional track measured

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How is the radius of Atlas sectional track measured
Posted by John-NYBW on Saturday, March 4, 2023 9:17 AM

Is it to the inside rail, outside rail, or track center? I'd like to use some in a switching area but it's a tight fit and I need to be precise if everything is going to fit.

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Posted by Water Level Route on Saturday, March 4, 2023 9:26 AM

John, my last 4X8 layout was built with Atlas 22" radius track at the ends.  Made a nice turnback curve with track centers 2" from each edge when done.  Has to be a centerline measurement.

Mike

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Posted by dbduck on Saturday, March 4, 2023 9:36 AM

the radius is  measured to the centerline of the track

have you considered using flex track?

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Posted by jjdamnit on Saturday, March 4, 2023 1:53 PM

Hello All,

dbduck
(T)he radius is measured to the centerline of the track have you considered using flex track?

Check out this thread for "tricky track" situations...

DIY Flex Track

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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Posted by John-NYBW on Saturday, March 4, 2023 3:01 PM

dbduck

the radius is  measured to the centerline of the track

have you considered using flex track?

 

Bending flex track to tight radii can be done but it is hard to get it to stay where you want. It's simpler to use fixed radius track if you can get it to fit. With 22" radius to the center, I think I can get it to fit the space I have. If the radius was to inside rail, that would make the curve just a bit wide and would have forced me to tweak something to get it to fit. 

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Posted by doctorwayne on Saturday, March 4, 2023 6:28 PM

John-NYBW
Bending flex track to tight radii can be done but it is hard to get it to stay where you want.

I can't see why it can't be bent to suit...simply use a nail, some string, and a pencil to draw the curve that you want, then put a few finishing nails at various places on the drawn curve, then bend the flex track to-suit, with a few more temporary nails on the inside of the track's curve.  It should stay inplace while you add Atlas track nails to the appropriate ties.

Wayne

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Posted by selector on Saturday, March 4, 2023 6:33 PM

I do what Wayne sez.  Draw out an arc representing the centerline of the curve, which will be the radius of the curve.  Fasten the track length of flex at one end with the center hole of one of the ties pegged/pinned/nailed to the substrate surface, and then proceed to nail the center holes where you find them along the centerline.  Works like a charm.  If you don't like nails showing, you can ballast and when it is hard, remove the nails. Or, like many of us do, use a thin sheen of acrylic latex caulking along the centerline and affix the tie bottoms to the caulking.  When it dries, remove the nails, and your rails are fixed where you want them.

However, sectional track is a lot quicker, and if laid carefully, can serve you very well.

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Posted by mbinsewi on Sunday, March 5, 2023 7:20 AM

I've also "adjusted" fixed radius track sections, for switching areas, but cutting the plastic strip under the track that connects the ties.

Mike.

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Posted by SeeYou190 on Sunday, March 5, 2023 8:25 AM

John-NYBW
I'd like to use some in a switching area but it's a tight fit and I need to be precise if everything is going to fit.

John, This is exactly what I do. Any curve 24" or below is done with sectional Atlas track. I have found it too easy to get something out-of-adjustment with flex track and have a short curve that is too tight. Atlas sectional track prevents this.

I have a supply of 24, 22, and 18 inch radius pieces for use in my industrial and switching areas.

I did this same practice on all previous HO scale layouts, and I had no problems with it.

Oh, as for your original question, as was already stated, the curve radius is the center line of the ties.

-Kevin

 

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Posted by ATLANTIC CENTRAL on Sunday, March 5, 2023 9:05 AM

SeeYou190

 

 
John-NYBW
I'd like to use some in a switching area but it's a tight fit and I need to be precise if everything is going to fit.

 

John, This is exactly what I do. Any curve 24" or below is done with sectional Atlas track. I have found it too easy to get something out-of-adjustment with flex track and have a short curve that is too tight. Atlas sectional track prevents this.

I have a supply of 24, 22, and 18 inch radius pieces for use in my industrial and switching areas.

I did this same practice on all previous HO scale layouts, and I had no problems with it.

Oh, as for your original question, as was already stated, the curve radius is the center line of the ties.

-Kevin

 

 

I also use sectional track for some tight industrial sidings, street trackage, etc.

Sheldon

    

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Posted by richhotrain on Sunday, March 5, 2023 9:10 AM

The Atlas terminology seems to have changed for its track that is shorter than flex track. At one time, its 22" radius curve and its 24" radius curve was referred to as "sectional track", and its 15" radius curve and its 18" radius curve was referred to as "snap track". More recently, all four radii curve track have been referred to as "sectional track".

Atlas sectional track does provide an accurate fixed radius curve in all four instances. That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale. I say this because most HO scale locomotives and rolling sttock are not designed to operate on curved track less than 22" radius. That's just my opinion from personal experience.

Rich

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Posted by ATLANTIC CENTRAL on Sunday, March 5, 2023 9:47 AM

richhotrain

The Atlas terminology seems to have changed for its track that is shorter than flex track. At one time, its 22" radius curve and its 24" radius curve was referred to as "sectional track", and its 15" radius curve and its 18" radius curve was referred to as "snap track". More recently, all four radii curve track have been referred to as "sectional track".

Atlas sectional track does provide an accurate fixed radius curve in all four instances. That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale. I say this because most HO scale locomotives and rolling sttock are not designed to operate on curved track less than 22" radius. That's just my opinion from personal experience.

Rich

 

Rich,

Do you know what locomotive I would be refering to if I said "B&O Docksider"?

These locos were used to switch industries and docks in southeast Baltimore. Most of the trackage was in the streets.

This was in an era when few freight cars were longer than 50' and the curves of this trackage were very sharp, even pushing 40' and 50' cars right to the edge.

Much of this trackage was built so far back most freight cars were 36', but this lasted well into the 1980's before most of it was abandoned. 

After the steam locos were gone, small diesels and later Trackmobiles supplied the motive power for this area.

Curves in the range of 175' radius (24" in HO) were very common in these kinds of locations.

So modeling these kinds of locations with curves as sharp as 18" radius is no different than any of our other selectively compressed trackage.

I remember this very intersection. When I sold MATCO TOOLS in the early 80's, a concrete plant in this neighborhood still received gravel, sand and Portland by rail on these tracks.

Sheldon

    

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Posted by John-NYBW on Sunday, March 5, 2023 10:18 AM

richhotrain

The Atlas terminology seems to have changed for its track that is shorter than flex track. At one time, its 22" radius curve and its 24" radius curve was referred to as "sectional track", and its 15" radius curve and its 18" radius curve was referred to as "snap track". More recently, all four radii curve track have been referred to as "sectional track".

Atlas sectional track does provide an accurate fixed radius curve in all four instances. That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale. I say this because most HO scale locomotives and rolling sttock are not designed to operate on curved track less than 22" radius. That's just my opinion from personal experience.

Rich

 

It's been a long time since I had a layout with 18" sectional track on the mainline but my experience is four-axle diesels and steamers as big as a Mikado could negotiate it without jumping the rails. I never had anything bigger than that in those days.

I have another switching area that uses a short section of 18" radius track and my BLI SW7 has no trouble handling that curve. It's the only loco that goes on that secion. The new switching area I'm building will be switched by a Ten Wheeler and would probably handle 18" radius but I have just enough room to put in 22" track so that's what I am going to go with. 

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Posted by SeeYou190 on Sunday, March 5, 2023 10:38 AM

John-NYBW
It's been a long time since I had a layout with 18" sectional track on the mainline.

18" radius is only used on industrial trackage. Hidden mainline curves drop to 22" radius. Visible mainline curves are at least 36". Visible branchline curves can be 24".

-Kevin

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Posted by John-NYBW on Sunday, March 5, 2023 11:05 AM

SeeYou190

 

 
John-NYBW
It's been a long time since I had a layout with 18" sectional track on the mainline.

 

18" radius is only used on industrial trackage. Hidden mainline curves drop to 22" radius. Visible mainline curves are at least 36". Visible branchline curves can be 24".

-Kevin

 

Standards on my current layout are very similar to yours. My branchline minimum is 28". I know I could go lower with the equipment I run but I think a little broader curves just look better. Motive power is a Ten Wheeler and a 55' Doodlebug. 60' passenger cars and no freight cars over 40'.

My previous layout had a mainline minimum of 28". It handled my UP articulateds and the FEFs but full length passenger cars just didn't look right going around curves that tight so I upped my standards when I started the current layout. 

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Posted by richhotrain on Monday, March 6, 2023 4:01 AM

ATLANTIC CENTRAL
 
richhotrain

That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale.

Rich 

Rich,

Do you know what locomotive I would be refering to if I said "B&O Docksider"?

Looks like I raised somebody's eyebrows. Laugh

Sheldon, methinks you play devil's advocate here since you and I both lust for minimum 40" radius curves on our layouts. Of course, my comments were a broad generalization that if one is building a layout and is forced by space considerations to use 15" and 18" radius curves, he just might be better off modeling in N scale. Grumpy

Rich

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Posted by richhotrain on Monday, March 6, 2023 4:05 AM

John-NYBW

The new switching area I'm building will be switched by a Ten Wheeler and would probably handle 18" radius but I have just enough room to put in 22" track so that's what I am going to go with.  

And, you should be happy with that track configuration, John. It is when we are forced to use tighter minimums than we otherwise would want on curves due to space considerations that problems arise.

Rich

Alton Junction

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Posted by ATLANTIC CENTRAL on Monday, March 6, 2023 6:02 AM

richhotrain

 

 
ATLANTIC CENTRAL
 
richhotrain

That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale.

Rich 

Rich,

Do you know what locomotive I would be refering to if I said "B&O Docksider"?

 

 

Looks like I raised somebody's eyebrows. Laugh

 

Sheldon, methinks you play devil's advocate here since you and I both lust for minimum 40" radius curves on our layouts. Of course, my comments were a broad generalization that if one is building a layout and is forced by space considerations to use 15" and 18" radius curves, he just might be better off modeling in N scale. Grumpy

Rich

 

The point is simple, even on my layout with its 36" minimum curves on the mainline, and anywhere large locos or passenger cars travel, there are industrial tracks with sharp curves.

You really want to see sharp curves and crazy trackwork on the prototype - look up the Bronx terminal. 

http://www.bronx-terminal.com/

This car float - rail - truck terminal used an oval warehouse, with oval tracks around the outside to unload railcars and trucks loaded inside the oval. The radius of the oval was about 90', or about 13" in HO.

Obviously this kind of industrial trackage is the ONLY place I would use curves this sharp - other than a trolley line.

Sheldon 

 

    

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Posted by IRONROOSTER on Monday, March 6, 2023 1:11 PM

richhotrain
That said, and this may raise some eyebrows, if someone needs curved sectional track as tight as 15" radius or 18" radius, N scale ought to be considered instead of HO scale. I say this because most HO scale locomotives and rolling sttock are not designed to operate on curved track less than 22" radius.

If you want tight radius use O gauge Smile, Wink & Grin.  Atlas 3 rail looks pretty good and most trains will run on O36 track (36 is diameter, radius is half that) and many will run on O27 track.

Paul

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Posted by Doughless on Monday, March 6, 2023 1:30 PM

I agree with OP, it can be difficult to bend flex track into sharp radius curves....short sections of flex track.

Code 83? 

For industrial situations, consider the ATLAS 22 inch radius turnout Item #544 and #545.  It has a curved diverging route (like PECO code 100 turnouts) that are designed to fit into a 22 inch radius curve.

I used these on a previous layout.  I like the look of the car cut diverging at a consistent curve through the tracks, rather than the curve...straight...then sharp curve motion you get with a standard #4 turnout that has a straight diverging path.

It also help with tight spaces since the track is already more sharply angled right after the frog.   

Works well and looks better, what's not to like.

- Douglas

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Posted by ATLANTIC CENTRAL on Monday, March 6, 2023 1:39 PM

Doughless

I agree with OP, it can be difficult to bend flex track into sharp radius curves....short sections of flex track.

Code 83? 

For industrial situations, consider the ATLAS 22 inch radius turnout Item #544 and #545.  It has a curved diverging route (like PECO code 100 turnouts) that are designed to fit into a 22 inch radius curve.

I used these on a previous layout.  I like the look of the car cut diverging at a consistent curve through the tracks, rather than the curve...straight...then sharp curve motion you get with a standard turnout that has a straight diverging path.

It also help with tight spaces since the track is already more sharply angled right after the frog.   

Works well and looks better, what's not to like.

 

I use the 22"R and 18"R Atlas "snap switch" for street trackage, they work fine for that sort of thing.

Sheldon

    

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Posted by jjdamnit on Monday, March 6, 2023 2:55 PM

Hello All,

John-NYBW
The new switching area I'm building will be switched by a Ten Wheeler...

By "Ten Wheeler" do you mean a 2-6-2, a 4-6-0, or a 2-8-0?

What size tender?

Type of fuel- -coal or oil?

That wheel configuration seems large for switching duties- -both in terms of length and fuel/water- -consumption.

On my HO 4'x8' pike the "mainline" consists of 180º asymmetrical curves at each end comprised of 15- and 18-inch sectional track, with 2-inch transitions between the differing radii.

My track plan allows for 0-4-0 and 0-6-0 locos along with four-axle diesels.

The upper and lower coal unloading/loading sidings are comprised of PECO #2 turnouts (ST-240 & ST-241). 

As is the wye made up of PECO #2 turnouts with two (2) 15-inch radius Atlas sectional track for the legs to an Atlas Mark IV wye turnout at the head end.

Rather than rethinking the track plan, I suggest you reconsider which locomotive can work this yard most efficiently.

Unfortunately, I've become adept at "shoehorning" track into small spaces.

This comes at the expense of smaller locomotives and shorter rolling stock with tighter curves.

In modeling, compromises need to be struck to achieve reliable running.

For this situation, I would err on the side of caution, using small radius sectional track and turnouts with smaller locomotives.

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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Posted by ATLANTIC CENTRAL on Monday, March 6, 2023 3:06 PM

jjdamnit

Hello All,

 

 
John-NYBW
The new switching area I'm building will be switched by a Ten Wheeler...

 

By "Ten Wheeler" do you mean a 2-6-2, a 4-6-0, or a 2-8-0?

What size tender?

Type of fuel- -coal or oil?

That wheel configuration seems large for switching duties- -both in terms of length and fuel/water- -consumption.

On my HO 4'x8' pike the "mainline" consists of 180º asymmetrical curves at each end comprised of 15- and 18-inch sectional track, with 2-inch transitions between the differing radii.

My track plan allows for 0-4-0 and 0-6-0 locos along with four-axle diesels.

The upper and lower coal unloading/loading sidings are comprised of PECO #2 turnouts (ST-240 & ST-241). 

As is the wye made up of PECO #2 turnouts with two (2) 15-inch radius Atlas sectional track for the legs to an Atlas Mark IV wye turnout at the head end.

Rather than rethinking the track plan, I suggest you reconsider which locomotive can work this yard most efficiently.

Unfortunately, I've become adept at "shoehorning" track into small spaces.

This comes at the expense of smaller locomotives and shorter rolling stock with tighter curves.

In modeling, compromises need to be struck to achieve reliable running.

For this situation, I would err on the side of caution, using small radius sectional track and turnouts with smaller locomotives.

Hope this helps.

 

A "ten Wheeler" is by definition a 4-6-0.

https://www.steamlocomotive.com/locobase.php?country=USA&wheel=4-6-0

Sheldon

    

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Posted by jjdamnit on Monday, March 6, 2023 3:19 PM

Hello All,

ATLANTIC CENTRAL
A "ten Wheeler" is by definition a 4-6-0.

I'm a diesel guy- -thank you for the clarification.

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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