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HO track radius

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  • Member since
    December 2008
  • 84 posts
HO track radius
Posted by Georgia Flash on Saturday, December 13, 2008 9:21 AM

 Hey guys:

I am a newbie to this forum; please bear with me. I have a 10ft X 23ft room built in my new house that is dedicated to my soon-to-be-constructed HO guage model railroad. 

I would like to have continuous running capability; therefore, "return" loops are required - yes? I also want to be able to walk/roll around the layout. My preliminary plans include a 12 to 18inch wide "shelf" along both of the 23 foot sides, ending in "return" loops. My first question has to do with curve radii - specifically, minimum radius that either reduces or eliminates that toy train, unrealistic 'swing-out/hangover' look as locomotives and equipment negotiate the curve in the 'return' loop. I prefer not to cover these curves with tunnel scenery.

Any tips will be appreciated. Thanks,

 

Georgia Flash (williams172166@bellsouth.net)

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Posted by mobilman44 on Saturday, December 13, 2008 10:08 AM

Hi!

Welcome to the Forum!!!  I think you will find it an invaluable resource and you will also enjoy the opportunity to help others as well.  I am currently in the process of designing the rebuild of my 11x15 HO room filling layout, so I can somewhat identify with your situation.

The layout you described sounds like it will be a "dog bone", which can be really fun to operate and can give a very realistic impression.  Regarding the radius question, the answer most will give you is to use the widest radius you can fit into the space allowed. 

Another factor is the type of trains / era you are modeling.  If you are running small steam and 8 wheel diesels, then a 24 radius would probably look fine.  Yes, many trains will handle an 18 inch radius, but the effect is toylike.  If you are running large steam / diesels or full size passenger cars, then I would consider nothing less than 26 inch radius - but would recommend 30 as a minimum.  Again, most of the larger locos / cars may handle 24 inch radius, but they are going to look toylike and the propensity for derailments will be ever present.

In any case, make sure you put in easements (from straight tangent track to the curved track).

Of course you could build an around the room layout, which would require a "duck under", but the radius recommendations still would apply.

ENJOY, and make yourself a regular here - you won't be disappointed!

Mobilman44

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

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  • From: Mount Vernon WA
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Posted by skagitrailbird on Saturday, December 13, 2008 11:50 AM

 Georgia Flash,

 Welcome from me, also a relative newbie to this forum.

I am somewhat confused by your description of two shelves along each of the long sides.  May I assume that there will also be a shelf along one of the short sides connecting the two long shelves?

With regard to your questions about radii, I agree that 24" is the practical (and aesthetic) minimum for shorter equipment (four axle diesels, smaller steam power and 40" or 50" cars).  Larger motive power and/or full scale passenger or modern freight cars ups the minimum to at least 30".  On my HO scale layout I run 86" passenger cars on 31" radius curves--they operate well but there is still considerable swing out/hangover.

In any event I would urge you to consider an around the room layout, even though that will require a duck under or lift out/up.  With minimum 24" radii, if you have a U shaped layout, each reverse/return loop would require a minimum of 50" for a total of 100" of your room width of 120", leaving only a 20" space to enter the center of the U.

In a room of your size you could easily build a very nice around the room layout.  I have operated on two such layouts (both in shorter rooms than yours) and they work very well with pretty wide curves in the corners.  Both of them are "twice arounds" giving very nice mainline runs.

 

Roger Johnson
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  • From: Southwest US
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Posted by tomikawaTT on Saturday, December 13, 2008 12:36 PM

Welcome aboard. Sign - Welcome 

In HO (or any other scale) track radius is driven by the rolling stock to be used.  If you want Big Boy, a brass NYC Niagara, 89 foot humonguboxes or 85 foot Pullmans you will have to allow for the 30 inch (or better) radii they demand.  OTOH, if you're modeling a mining route that moves 24 foot ore jimmies with SW diesels or small tank locomotives, 15 inch radii are not unreasonable - until the day you succumb to temptation and buy that (fillintheblank) that just doesn't fit.

I agree with the others that a true 'around the walls' design with a moveable entrance (not, for any reason, a duck-under - unless you're planning the benchwork to be somewhere near your standing eye level!) will probably be easier to live with than a true dogbone.  With 10 feet to work with, two reverse loops side by side will only leave about 20" for an aisleway, and no elbow room.  My personal preference for a moveable entrance is a swinging gate or Dutch door arrangement.  Several good designs have appeared in the Forums and the modeling press.

For future planning, you might think about how you could incorporate a second level of shelves, either higher or lower than your first, for later development.  Model railroads have a tendency to expand!

Chuck (Modeling Central Japan in September, 1964)

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  • From: Martinez, CA
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Posted by markpierce on Saturday, December 13, 2008 12:39 PM

George,

These two sites will tell you what you need to know about track radii:

http://www.macrodyn.com/ldsig/wiki/index.php?title=Curve_radius_rule-of-thumb

http://www.nmra.com/standards/sandrp/rp-11.html

The Layout Design Special Interest Group and the National Model Railroad sites have lots more of useful trackplanning information such as turnouts (which also have curves.)

Your question is asked constantly on this forum.  The moderators would be doing everyone a favor if they kept the above information as a "sticky."

Mark

  • Member since
    April 2003
  • From: Martinez, CA
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Posted by markpierce on Saturday, December 13, 2008 2:45 PM

Georgia Flash

My first question has to do with curve radii - specifically, minimum radius that either reduces or eliminates that toy train, unrealistic 'swing-out/hangover' look as locomotives and equipment negotiate the curve in the 'return' loop. I prefer not to cover these curves with tunnel scenery.

If you have an around-the-walls configuration where the curves are viewed from the inside and not too far from eye level,, train appearance will improve because you won't be seeing an enlarged gap between cars when they go around the curves.

Mark

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    March 2003
  • From: Scottsdale, AZ
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Posted by BigRusty on Saturday, December 13, 2008 3:43 PM

The dogbone is my favorite track scheme. I have used it in my last three layouts. It can provide a two track mainline in the center with staging in the return loops. In your case, the return loops should not be placed opposite to one another. Just place one as far as possible along one of the 23 foot walls and then on the opposite wall locate it farther back to provide at least a three foot access to the center without need for a duck under, You can gain additional track mileage by gradually increasing the grade before the second loop and run a high line around to a loop staggered over the first loop.

I always used 30 inch minimum radius which results in a 32 inch outer track in a loop and about a total 66 inches in diameter.

I would place my center of interest on the 10 foot wall so that trains leaving to the East, eventually arrive back  from the East rather than the West as they do in roundy round type layouts.

Modeling the New Haven Railroad in the transition era
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Posted by dstarr on Sunday, December 14, 2008 2:44 PM

 It's like this.  18" is so tight that long cars and locomotives derail going around them.  They limit you to 40 foot freights and smaller engines.  30 inches will run anything and look good, but a 30 inch radius means a 60 inch (5 foot) diameter for the return loop.  Since your room is only ten feet wide, a pair of five foot return loops may be hard to fit in.  Large radius curves are worth having, so you ought to try and fit in the biggest curves you can.  Compromise radii are things like 22, 24, and 28 inch.  Larger is better.  

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Posted by lvanhen on Sunday, December 14, 2008 3:33 PM

Absolute minimum 24" - even in a hidden area!  Better yet 36" min to make the cars look less "toy-like", and larger for an even better appearance.Smile

Lou V H Photo by John
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  • From: Omaha, NE
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Posted by dehusman on Sunday, December 14, 2008 3:37 PM

Georgia Flash
I would like to have continuous running capability; therefore, "return" loops are required - yes? I also want to be able to walk/roll around the layout. My preliminary plans include a 12 to 18inch wide "shelf" along both of the 23 foot sides, ending in "return" loops. My

Return loops aren't required.  You can just go all the way around the room and have a lift out or duckunder across the door.  If you use return loops than you will have two main lines through each scene, which for 12 in wide brenchwork is a lot of track in a narrow space.

Rather than decide what radius, why don't you see what radius you can use?  that depends if you are using the return loops because you have to (you MUST have walk in access)  or if you are just including them because you think you have to have them.)  If you for some reason HAVE to include return loops, can you stack them?

The room is 10 feet wide so that makes about 56" radius your absolute max.  Assuming a minimum aisle width of 30" and bench width of 18" that makes one aisle and bench 4 feet wide.  In a 10 ft wide room that gives you 6 feet of room for a return loop.  So you have the ability to fit 32" radius return loops easily.  If you stack you return loops you will only have 1 "footprint" for the return loops.  but if you do that, why have return loops at all, just make the benchwork 24-30' wide and go twice around the room. Way simpler to operate and wire.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by BigRusty on Sunday, December 14, 2008 4:12 PM

In any event I would urge you to consider an around the room layout, even though that will require a duck under or lift out/up.  With minimum 24" radii, if you have a U shaped layout, each reverse/return loop would require a minimum of 50" for a total of 100" of your room width of 120", leaving only a 20" space to enter the center of the U.

Think out of the box. A 36" min radius double track loop would be less than 84 inches wide leaving a 36 inch wide access.This is accomplished by just setting the opposing return a few feet back along the other 20 foot wall.

Modeling the New Haven Railroad in the transition era
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  • From: Suffolk, VA
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Posted by ken_23434 on Monday, December 15, 2008 9:16 AM

I assume the door must be in one of the 10 foot walls since the shelf will be on the 2 23 foot walls.  A lot of people have talked about the loop backs taking up so much room and not leaving much room between them to walk.  To me, it sounds like those loops will end up being on the last 10 foot wall, the one with the door.  The five foot wide loops people have recommended will not allow room for the door.

If the door is centered on that wall, you would need to make at least one loop back more towards the center of one of the 23 foot walls.  The edge of the loop would need to be maybe 7 or 8 feet from the wall with the door, so the two loop backs are staggered to allow room to walk between then and room for the door.  If the door is in the corner, then there is no question which of the 23 foot walls will have the shorter one.

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