# HO Mainline Size Question



## grpaine (Jun 18, 2016)

I want to build an HO layout and I’ve been looking at a lot of people’s layouts for ideas. I don’t want a rectangle, duck-under, lift-out, swinging gate or access hatches. I’ll have all around access; it will be free standing. I guess that leaves me with some sort of walk-through; L U or walk-in.

One of my requirements is a main line (or two) where I can just let a train run. I would like passenger cars on the main but also be able to ‘park’ those passenger cars elsewhere on the layout (a yard or passing track). The planning book I have says for HO use 30” radii turns for mains with passenger cars; 24” radii with easements is acceptable for passenger cars (in most cases). 

Using SCARM, I created a layout, in an L design, with 30” (blue and green) and 27” (red) radii mains, just to see what it looks like. The smallest layout I could make with those requirements consumes almost 12’ x 12’, with the track right up to the edges. I do not have straight pieces between the S curves, which would make it larger.

Before I proceed any further with the layout, am I correct or am I doing something wrong? I expected there to be more straight track for 12’x12’.


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## Mark VerMurlen (Aug 15, 2015)

Your drawing looks correct to me. A 30" radius results in a circle that's 5 ft across. You have a lot of partial circles in your design, so you'd need 15 ft to get 3 complete side-by-side circles that are tangent to one another.

You're experiencing the feeling that we all have when we realize how hard its going to be to get the broad curves that we'd all really like to have.

Mark


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## fcwilt (Sep 27, 2013)

Hi,

Broad curves take up space.

On my layout I was able to get 30" curves as a minimum on the mainline.

The layout is about 21' by 13'.

Because of limited space I had to put the staging yards on a lower level.

See attached.


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## Genetk44 (Feb 26, 2016)

The other thing is those interior curves and the S-curves leading into them can be come problematic.


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## DonR (Oct 18, 2012)

If you intend using long passenger coaches you might
want to insert short straight sections to break
the S curves in the blue tracks. The ends of the
cars protrude away from the track and they would
be fighting each other on the S.

If you will be running DCC add passing sidings to
your single track main so you can run trains going in opposite
directions.

You definitely would want a yard and some spur
tracks for switching sessions.

Don


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## CTValleyRR (Jul 26, 2014)

grpaine said:


> I want to build an HO layout and I’ve been looking at a lot of people’s layouts for ideas. I don’t want a rectangle, duck-under, lift-out, swinging gate or access hatches. I’ll have all around access; it will be free standing. I guess that leaves me with some sort of walk-through; L U or walk-in.


If you're putting that condition on your layout, then you're stuck with what you have: big lobes for the loops where the train goes around the end.

The only solution is to use sharper curves -- which comes with it's own set of problems. Long passenger cars require broad curves, and don't like S curves either. 

My advice would be either suck up the space requirement, or, if not an option, then accept a gate, lift-out, or duck under.


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## grpaine (Jun 18, 2016)

Thanks for confirming the amount of space consumed by looping a broad mainline around. I was surprised when I saw it in SCARM and hoped I was doing something wrong. Time to think about this some more. 

Thanks again.


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## fcwilt (Sep 27, 2013)

grpaine said:


> Thanks for confirming the amount of space consumed by looping a broad mainline around. I was surprised when I saw it in SCARM and hoped I was doing something wrong. Time to think about this some more.
> 
> Thanks again.


My layout (posted) was an exercise in compromise after compromise.

It took me a long time to come up with a plan that did the things that were most important, none of the things I really didn't want and yet was something I could actually have a hope of building before I'm dead and gone.


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## Cycleops (Dec 6, 2014)

If you'll be running this from the rh side of the layout you won't have much room for a yard to assemble trains plus they'll be on the edge where they can be knocked off. It looks like a multi level mountain setting with trains going in and out of tunnels. Is that correct? If so you'll need to think about access to the track.


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## wvgca (Jan 21, 2013)

If you intend modern era with passenger service, larger radius not only looks better, but also works better ... the older the era, the shorter the cars [and loco's] can be with a corresponding smaller workable radius ..
I model 1890, short cars and loco's, 18" minimum radius, most are 20"


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## grpaine (Jun 18, 2016)

fcwilt said:


> Hi,
> 
> Broad curves take up space.
> 
> ...


The 3D image looks like it is a 3 level layout? The next design I want to try is similar to yours. Change the L to a U and extend one leg and loop past the shorter leg and loop. Would you be interested in sharing your SCARM file so I can look at your layout in more detail?


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## grpaine (Jun 18, 2016)

Cycleops said:


> If you'll be running this from the rh side of the layout you won't have much room for a yard to assemble trains plus they'll be on the edge where they can be knocked off. It looks like a multi level mountain setting with trains going in and out of tunnels. Is that correct? If so you'll need to think about access to the track.


At this point I am just experimenting to determine how much real estate would be required for my main. Then I'll have to add borders to get the track away from the edge, yards, passing tracks, etc.


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## grpaine (Jun 18, 2016)

wvgca said:


> If you intend modern era with passenger service, larger radius not only looks better, but also works better ... the older the era, the shorter the cars [and loco's] can be with a corresponding smaller workable radius ..
> I model 1890, short cars and loco's, 18" minimum radius, most are 20"


I just looked at the photos of your layout; nice job !!!!


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