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A  basic "think about it" for any newby planning  to build.

One of the biggest concerns in building a layout is sharp curves and short tangents. 

It is an undisputable fact that any island style platform layout will have shorter straight-a-ways, sharper curves and occupy a greater portion of any train room than what else could be built in the same area with an around the wall style layout.

If at all possible or practical, an around the room layout will also  provide a larger congregating central area.

Just consider it.........especially if your interest is large locomotives, long passenger cars, long freight trains.

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@Tom Tee posted:

HO or N

Bite your tongue!   

You're right of course.  In all seriousness I've struggled with this issue first-hand.  I've come to believe that in many ways the size of your room (along with your operating preferences) dictates what your max curve should be.

For years I collected "scale" (hi-rail) trains, with hopes of building a "big layout."  When I went to buy a house, reality hit me hard.  (I live in the Land of No Basements.)  My train room is 11 x 18, and living in the Sun Belt I doubt I'll ever have more than that.  Yes, I could do concentric ovals of O72 and O81.  This would allow me to run anything, but it leaves only 10' for straightaways.  That's not much when you consider that a Big Boy, A-B-A set, etc. are over 3 feet long, it doesn't leave much for the train!  Some people would be thrilled with a setup like this, because all they really want is a stage to display their locos in motion, with a bit of scenery along the right-of-way to provide some context.  But I stopped building that layout because I was afraid I would be bored with it before the paint was dry.

I want my railroad to be a highly-functional integrated system, not only a stage to display my locos in motion.  So it's tough for me to justify "a loop of O72 around the outside" just to occasionally run the Big Boy in circles.  I kept thinking of how that space would be better used to create alternate routes, sidings, yard, etc.  The only solution, a radical one, was to move away from scale and back into "traditional" O gauge.  Maybe Lionel was onto something when they re-emerged into the postwar world of 1946?  I hope the sharper curves will give me the operating variety that I crave.  Thankfully, with smaller Legacy locos, RailKing, and LionChief Plus, sharp curves and smooth operation at slow speeds are no longer mutually exclusive!  And the smaller locos will look just as good on O42 as the larger ones would have on O72.

During this time of soul-searching I also realized that I'm not a scale modeler.  I've never weathered, or ballasted, or painted anything in my life!  So with more room the trains might be scale-sized, but the overall result wouldn't be any more realistic than Postwar running through Plasticville.  Like many of you, I grew up with that, and it inspires my imagination to this day.

There's no one best way to enjoy this hobby.  But geometry is a cruel master.  Wider curves mean shorter straights, and I do believe that the size of your room strongly suggests your max curve, train length, etc.  My $.02, worthy subject!

Last edited by Ted S

There's a secondary benefit of going around-the-walls vs. the island-in-the-middle. The physics of running the train. With the island, you see the entire layout (assuming no view block in the middle). It makes the layout look smaller. Additionally, you see equipment rounding the curve from the outside which exaggerates the "coupling gap", plus you see the rails bowing out underneath the cars.

With an around-the-walls, you can't see the entire layout (unless like some moms you also have eyes in the back of your head). This forces you to follow the train's motion. You also see the equipment from the inside of the curve which reduces the coupler gap. With longer cars, you don't see the rails bowing out from underneath which hides the sharpness of the curves.

Speaking of sharpness, the island will require sharper curves. In a 12'x12' room, you're pretty much limited to an 8'x8' island (or 8'x10' peninsula) for 2-foot aisles. This limits your curves to 44" radius (O-88) and 48" of straight between them maximum fir 96" of straight total. Using 2-foot shelves on around-the-walls, using that same 44" radius (O-88), you can have twice as much straight track (192") using a square layout with a lift-out corner. In the example below (42" radius/O-84 with 4" extension of straights, plus a beveled corner for a lift-out), the straight trackage totals 175" (some loss of straight because of the bevel). It allows for placement of a passing/run-around siding.



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Last edited by AGHRMatt

Another option to around the room or an island shapes is an L shaped layout against two walls.  The two legs can be 12 ft long and each 5 ft or 6 ft wide.  An outside loop can have larger that 027 curves. 

An average reach from an edge is at least 4 ft, maybe 5 ft if tall.  Grabbers can be used to reach farther or one length can be shortened to 11 ft to help access. 

My 40 year old layout is near the sizes mentioned above but the layout was on the floor for 30 years and strong enough to walk on.  It is full of 027 track with 31 switches where as your talking about a simpler single track plan with bigger diameter curves which will allow access panels to be used to reach along the walls.

The choice is limited track with large curves or sharper curves and more track with multi loops and switching an option.  How do want to operate or watch your trains?

Train Overhead views 9-21-016 2016-09-21 014


Last edited by Choo Choo Charlie

These are all good and insightful comments.

Just to be complete, the island arrangement offers access around 360 degrees, or if one side is against a wall, 270 degrees.   Around the walls is perfect in access and reach, but from one direction only.

Around the walls generally allows more space and opportunities for industries and passing sidings and a yard, so one can operate the trains realistically, making a run servicing industries.

Viewing angles are sharply limited with around the walls, you can only see the layout and trains from one vantage point, that is, the side that is not against the walls.  I appreciate being able to see and watch trains from many angles as they do their thing.

Arround-the-walls requires at least one door and access into the layout, requiring a lift-out bridge or some such solution.

So perhaps the "ideal" arrangement is around the walls for wide diameter and smooth running, with a peninsula in the middle with (perhaps) a tighter diameter to make the curve-back.  For instance O72 around the walls, but O54 in the peninsula.  The two make a connection (various arrangements are possible).  If both feature a loop, then two trains can loop/circle without intervention for train watching, or for letting the trains run while you are working on structures or details.

I tend to like a double-track main around the walls, so I can see trains running in both directions.  Then as part of the peninsula or its connection to the around the walls, design at least one reverse connection to turn trains around.  This also facilitates the out and back running scheme: from a yard out and around, turning direction, and return back to the yard.

Last edited by Ken-Oscale

The "if at all possible or practical" is far more limiting than you might think.  An around the wall layout for me would have meant dealing with two separate doorways.  Even though I could design around that I still was faced with a second limitation that the room had to remain useable for other purposes.  That included being able to open and close windows on the exterior walls.  For the right modeler with the right space an around the wall layout may be the best option.  For different modelers with different spaces around the all with a peninsula, an island or a traditional or dogbone L shaped layout may prove to be better options.

Which brings us to the "should larger curves be a goal" issue.  Larger curves look more realistic and they open up operational possibilities.  They also chew up a great deal of space.  Moving from O-42 to O-72 is going to chew up a lot of ground that could have been used for longer tangents or other purposes, even with an around the room layout.  It creates more dead space in the corners.   When it comes to curves the rule shouldn't be "bigger is better".  The rule should be "big as they need to be" with need being determined by aesthetics and operational requirements as well as the size of the room.

Access to the trains is a big one for me.....if the trains are "work" to change out.....then I tend to run less varieties of engines and rolling stock.......I am getting a 22x30 attic room next spring. I have 3 doors that I will need to deal with (which would make around the room tough, anyway). However, what I really want is the wall to have multiple shelves to display  the trains and give me easy access to them. 

Here are a few tentative plans (you will easily see that I get a lot of great ideas from reading the threads of Ken OScale....)


All feature wide curves and leave room to get around on all sides (this is a 30x20 ft space, so I have 2 more feet on the bottom of all the plans to widen the lower aisle).

My desk  and computer will also be up there is the lower L corner.

I have a long time to plan.....what I am doing is sitting on the plans and thinking them through....the last one, with the Y, is my favorite (the Y is an idea from oner of Ken's recent and wonderful plans).

The large L's use a Mianne lift bridge to get in the center.

The shaded area (on the 3rd one) is a proposed rolling city scene



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