Radius Question

[quakers1]

Hello,

In the past month, a new oppurtunity for a model railroad has opened for me: I found out that i can have a 12'x30' room for layout usage! This has opened up the possibility of HO Scale for me, which makes me thrilled, but I have one question. Since the room is not too wide, I am a bit limited on how wide of curves I can make.

As far as equipment, the largest I will be running is big six-axle diesels such as the SD75M, C44-9W, and the C40-8W. A large amount of the fleet will be 4-axle, since I plan on modelling the Santa Fe in the 1990's. Largest freight cars will be 89' TOFC Cars and 89' Auto Carriers. Since said cars will be in abundance (I am going to model a section of the Transcon), what would be a good turn radius to ensure smooth operation?

If general benchwork plans help out with this, I plan on having around the walls, with a large peninsula down the center. The layout will also likely be two levels (depends on what Transcon section i finally select...I am deciding between Amarillo-Clovis, or Clovis-Belen). The helix and the staging will be in an adjacent room.

So, as I asked earlier. What is a good radius that will allow smooth operation for trains with larger equipment (C44-9Ws, 89' TOFC Cars, etc)? Thanks for any and all help!

Cheers,

-Skylar

 

[zoegraf]

Hello,

In the past month, a new oppurtunity for a model railroad has opened for me: I found out that i can have a 12'x30' room for layout usage! This has opened up the possibility of HO Scale for me, which makes me thrilled, but I have one question. Since the room is not too wide, I am a bit limited on how wide of curves I can make.

As far as equipment, the largest I will be running is big six-axle diesels such as the SD75M, C44-9W, and the C40-8W. A large amount of the fleet will be 4-axle, since I plan on modelling the Santa Fe in the 1990's. Largest freight cars will be 89' TOFC Cars and 89' Auto Carriers. Since said cars will be in abundance (I am going to model a section of the Transcon), what would be a good turn radius to ensure smooth operation?

If general benchwork plans help out with this, I plan on having around the walls, with a large peninsula down the center. The layout will also likely be two levels (depends on what Transcon section i finally select...I am deciding between Amarillo-Clovis, or Clovis-Belen). The helix and the staging will be in an adjacent room.

So, as I asked earlier. What is a good radius that will allow smooth operation for trains with larger equipment (C44-9Ws, 89' TOFC Cars, etc)? Thanks for any and all help!

Cheers,

-Skylar

If I had that space I wouldn't go less than a 48 inch radius on the mainline. For me, passenger equipment looks better on a larger radius than 48 inches though. For freight, I'd go no less than 36 inches.

 

[Selector]

Your question will have answers based on the wise attribution of weighting to the responses of still more questions.

What I mean is, no one should design a layout based solely on the widest possible curves. To get to the point of being ludicrous, one only needs the circle with the widest possible diameter...which would soon be horribly boring. At the other extreme lies switching layouts on one wall where the only curves are those provided by long turnouts in the order of #10 and up. Lots of interesting operations, but not a lot of photo fun unless one is willing to do a ton of work toward industrial realism.

You have a generous space, but how do you propose to use it? What framework will you build to support it, and then how much of a reach into the space will it afford you at all points where you will need access?

If you wish to use the space effectively, curves are a driving force, no doubt, but how about visual and operating appeal? What will the terrain be like...research the railroad(s) using the area. What industries do you contemplate? Will they be partway up hillsides? If it is all flatland running, then you can run a wide shelf all around the room with a slide-out to free doorways. In that case, you are likely to be able to run a main as wide as 36" curves, depending on the width and depth. But, I only ask those questions because you used the term 'modeling', suggesting to me that you will make an attempt at realism in the two districts you mentioned in your post.

If photography and looks are likely, even in a couple of years or more, to be something that could interest you, look to get the widest curves you can, but place them in places where you can image them for maximum wow factor. Also, make some effort to superelevate the curves just a wee bit.

 

[quakers1]

Your question will have answers based on the wise attribution of weighting to the responses of still more questions.

What I mean is, no one should design a layout based solely on the widest possible curves. To get to the point of being ludicrous, one only needs the circle with the widest possible diameter...which would soon be horribly boring. At the other extreme lies switching layouts on one wall where the only curves are those provided by long turnouts in the order of #10 and up. Lots of interesting operations, but not a lot of photo fun unless one is willing to do a ton of work toward industrial realism.

You have a generous space, but how do you propose to use it? What framework will you build to support it, and then how much of a reach into the space will it afford you at all points where you will need access?

If you wish to use the space effectively, curves are a driving force, no doubt, but how about visual and operating appeal? What will the terrain be like...research the railroad(s) using the area. What industries do you contemplate? Will they be partway up hillsides? If it is all flatland running, then you can run a wide shelf all around the room with a slide-out to free doorways. In that case, you are likely to be able to run a main as wide as 36" curves, depending on the width and depth. But, I only ask those questions because you used the term 'modeling', suggesting to me that you will make an attempt at realism in the two districts you mentioned in your post.

If photography and looks are likely, even in a couple of years or more, to be something that could interest you, look to get the widest curves you can, but place them in places where you can image them for maximum wow factor. Also, make some effort to superelevate the curves just a wee bit.

Hello there,

First off, thanks to everyone who left me a response.

The two different Transcon areas I have in mind have greatly different terrain. The Amarillo-Clovis route is virtually ALL flatlands, with the exception of the Red River bridge, where the terrain gets a little more variable. Bout the only industries here would be some grain facilities.

The Clovis-Belen route is longer, so it would be two decks (helix will be in an adjacent room. The terrain is generally flat in some areas, but places such as the Abo Canyon offer some grades. No real industries on this route (its high-speed railroading at it's best), except for an area near Belen that has several, which is a relatively flat region.

Framework for the railroad is not 100% decided just yet. I will probably wind up using the old-fashioned open-grid.

And yes, I was thinking superelevation should help. I had plans to do that anyway because not only does it seem to help operations, it looks plain amazing!

Thanks for all the help!

-Skylar

 

[cuyama]

John Armstrong noted that choosing a radius that is too large for the room can be just as bad as choosing one that is too small. 48" is indeed enviable, but it will significantly limit what one can do in the space versus smaller radii.

This is especially true in a space that is significantly narrower than it is long, as it makes it harder or impossible to put a turnback "blob" on the center peninsula while still maintaining walk-around aisles.

If your desire is to optimize appearance and you are willing to sacrifice the amount of layout in the space and its arrangement, then the broadest possible radius may be a good choice. But if you wish to balance the amount of layout, appearance, and reliable performance, a smaller minimum radius may be a better overall choice.

Model railroad physics (which are entirely different than the prototype) determine that super-elevation does not help model trains go around tighter curves. It's great for suggesting the appearance of a high-speed mainline, but does not help performance in the model.

Handy rules-of-thumb for determining minimum radius from the Layout Design SIG.

As a point of reference, my multi-deck design for the Amarillo Railroad Museum occupies a space of about 50'X75' for their layout of Canadian, TX to Farwell, TX, including Amarillo's Junior Yard. Their space is significantly larger than yours, yet they chose a minimum radius of 48". And there were many times during the design that I wished it were 36" or so.

48" radius minimum in your space seems very constraining to me, but it all depends on what you want from your layout.

Best of luck.

Byron

 

[Outback]

Handy rules-of-thumb for determining minimum radius from the Layout Design SIG.

TY sir for that link. Some great info there that I wish I had when I was laying track. As it stands now I am a couple inches out of the rule of thumb and my track works but could be better in the curves if I had gone 2 inches wider. I'm running 20" radius where a 22-24 would have worked better. Problem is, the desired placement of the mainline dictated how tight the curves were to end up as fitting all other componants into workable space limitations would have become quite the connundrum with larger curves.

 

[Cjcrescent]

Bryon;

Went to the site and read your explanation of the plan. I wish that more folks on here would describe their layouts like this. It would really make it easier to help them.

I've never been to that area of Texas, but because of your description I could see those SF trains working that line.

Fantastic description!

 

[cuyama]

Bryon;

Went to the site and read your explanation of the plan. I wish that more folks on here would describe their layouts like this. It would really make it easier to help them.

I've never been to that area of Texas, but because of your description I could see those SF trains working that line.

Fantastic description!

Thanks! It turns out there's a lot more to layout design than just drawing a mess of lines with CAD.

Most people can't describe their layouts in this way because they haven't put much thought into the story they are trying to tell or the experience that the viewers and operators will have.

Byron

 

[D94R]

12' x 30' sounds like a lot of room, till you start forming curves like the many people above me has mentioned.

Broad curves look great, and the wider they are the better they tend to perform as the cars you use get longer.

But you said you are doing around the walls with a center peninsula. I assume you would be doing the peninsula down the middle of the room length wise. This makes your 12' wide room start to seem small once you realize how much room curves are going to consume.

Let's say for instance you want 36" minimum radius curves. To go along the wall and turn 180* to enter the peninsula that will eat up 72", or 6 feet of your 12' wall. Now, go out the peninsula and turn another 180* to come back and you will be consuming 6' in the center of the room at the widest spot, leaving at most 3 feet on either side of the peninsula for the "around the walls" portion. This doesn't even take into account the 3-4" you should leave on the outside of the track work to allow for derailment room. Doing this wide of a curve means that you are going to overlap the entering curves of the peninsula. A grade will help keep the track seperated. But this makes you consider two options. Either force yourself to switch aisles everytime you enter the peninsula for maximum track work and run time, or eat up valuable real estate with more curve trying to get your track back on the correct side of the peninsula. Neither produce a viable (to me) solution if I'm wanting a fun running layout. Wide curves also create the problem with adequate aisle space. Anymore than one or two people and you will run into issues. If the wall layout width is only 1', this leaves you with less than 2' of aisle space at the narrowest point.
See the below diagram as I assume you propose it with broad 36" radius curves on the left. Compare this to the same design using 24" radius curves on the right and see how much you gain by sacrificing radius. 24" may be considered these days to be too little to look perfect with long cars, but you can hide overhang around the curves with scenery and such.

You can see, with the smaller radius you can get longer "straight" runs which allow more options of turnout locations if you oppose curved turnouts. It also gives you wider aisles at the narrowest points between benchwork. This also allows you to run really wide curves on the bottom of the layout if you so wish for those beautiful sweeping curves. The top radius curves can even go up to 30" radi without interfering with eachother.


This is not to tell you how to do it, just to show you how you will be effected by large radi in what seems like a generous width of a room.

 

[Cjcrescent]

Thanks! It turns out there's a lot more to layout design than just drawing a mess of lines with CAD.

Most people can't describe their layouts in this way because they haven't put much thought into the story they are trying to tell or the experience that the viewers and operators will have.

Byron

I do some custom layout design on the side, and I have found that the layout has to be "described" a minimum of twice. Once by the client in filling out a trackplanning form I use, which describes era, area, RR, traffic type, industries etc and then described by me when I start sending versions of the plan to the client for their approval. I have found that the plans that turn out the best are the plans that are described the best.