couple of layout planning questions

[6axlepwr]

I have finished the first pass on the design of my layout. A few things I wanted to ask opinions on.

1. I understand I should use the largest radius possible for a smooth transition. What is your opinion of what the minimum radius should be?

2. The layout is based a a specific interchange. Basically the layout is built around this interchange. The shortest siding will hold about 23 to 26 cars. The longest siding will hold about 30 to 34 cars. The longest car is about 3". Using 70 ton and 55 ton coal hoppers. Other cars would be the PS-2 cement hoppers. So a mix of 55 ton and 70 ton hoppers will yield a lot of cars in this yard. The question I have here is In N-Scale, would that be considered a decent siding?

My tail track would hold about 15 cars with three locomotives if I needed to do a shoving operation. CPT&C cannot enter the MP main without a track warrant. With the current operation though there should not have to be any shoving. I used the track plan from the actual Missouri Pacific track schematic and then found a 1963 aerial shot of the area on Historic Aerials web site. I bought the photo and it really helped me nail the track plan. Plus it gave me the other operation that my railroad would have jointly served with the MP. A grain elevator.

As soon as I get the plan set, I will start an official thread on it.

Brian

[NtheBasement]

Short hoppers will work on 9 3/4" radius curve, as will all my Atlas and Kato diesels.  11 inch curves will both operate well and IMO look good enough with short hoppers and diesels.  Not everyone will agree on the looks though.

Only rule for passing sidings is make them a bit longer than the longest train.  Yard tracks can be anything; my longest hold maybe 15 coal hoppers.  If you don't have to compress anything, make them as long as the trains that come in and exit the yard.  Nice to have that kind of luxury.

[John]

I don't want to disagree - but 9 3/4 inch track should be banned for reliable running .. I'd say the absolute min is 15" or so .. IMHO

[6axlepwr]

These are not passing sidings. It is a four track interchange yard.

I do like the 15" rule John. I have one curve that is 10.5". I will negotiate with the plan and make it no smaller than R15"

Brian

[John]

These are not passing sidings. It is a four track interchange yard.

I do like the 15" rule John. I have one curve that is 10.5". I will negotiate with the plan and make it no smaller than R15"

Brian

You will get other opinions -- but tray your longest loco and attach the longest car you plan on using to it .. see how it does ..

[jagged ben]

My opinion:

16" absolute min for industrial spurs and/or if you need to compromise looks.  Anything less may involve equipment restrictions (although there are prototypes for that).

For mainlines, 21" in visible areas or on grades (which I guess you may not have) or 18" in flat hidden areas (may also not apply in your case). 

But my goals are to run long trains.

[dem34]

If your in planning stages now, get a handful of Unitrak and translate some of your forseen tricky areas into it. (TBH you can also get away with freebie code 80 pinned into foam) Mess around with it a bit, do some simple ops. It'll give a greater degreee of practical perspective in what you can and can't do, if you like the look, possible changes etc. With the added advantage that it is no sweat if you want to completely revamp since you didn't spend hours carefully laying it. Not perfect of course, options in snap track get thin around the golden zone of radii. But it can always just give a little perspective that might get overlooked just staring at a computer generated image.

[oakcreekco]

My opinion:

16" absolute min for industrial spurs and/or if you need to compromise looks.  Anything less may involve equipment restrictions (although there are prototypes for that).

For mainlines, 21" in visible areas or on grades (which I guess you may not have) or 18" in flat hidden areas (may also not apply in your case). 

But my goals are to run long trains.

Agree with 21" on main lines, but I do have plenty of 89' cars. They just look better to my eyes.

Don't forget to consider super elevation on the curves. Makes a difference again IMO.

[wm3798]

There's a big difference between minimum "functional" curves and minimum "aesthetic" curves.  It's okay to dip down a little in the radius department as long as you can confidently run a train through it, and effectively bury it in the scene so it's not obvious.



When I built my "big" layout, I was geographically limited due to the entry door location and the fact I was working in an attic with a sloped ceiling.  The maximum table top I could work with was 36" deep, and I had a pretty specific scene in mind, so the return loops needed to be no more than 15" radius.  You can see the two main lines diverge at the junction to the left, then split and cross one over the other at the right in the image above.  Fortunately, I model an Appalachian road, so there's lots of lumpy green scenery in which to conceal such eye sores.  But this gave me the absolute minimum radius that knew I could use for my main line traffic.

Then only place I strayed from that was a small helix that was necessitated by another stack of scenery at the other end of the layout, where the Thomas Sub had to climb up to a narrow shelf where I built a small representation of Elkins.  The helix, if memory serves, pinched down to 11", but that was fine, because that was part of a branch line whose primary traffic was 55 ton coal hoppers.  My only concern was having it "loose" enough to run my 2-8-0 up and down under load (10 cars) without any problems.  Fortunately, 11" turned out to be just enough to get away with it.  This tight turn was also concealed, this time by a curved skyboard behind what would become Cumberland.



In both cases, I tested the run, and tested it again, using what were the longest cars/loco combinations I had available.  I also tried backing maneuvres, and trials of body mount and truck mounted coupler combinations.  Once I was satisfied that the grade and the curves were reliable, I glued it all down and wired it.  Once the scenery was built to mask the curves, I feel like the trackwork, as well as the illusion, were well worth the effort.





For the more visible trackage, I kept things on pretty sweeping curves.  This provided enough eye candy to distract the brain into thinking that the trains were running along a valley that went on more or less forever.  I used other scenery tricks to break the scenes up into vignettes, which helped to perpetuate the illusion.





And this doesn't just work on big room filling layouts.  On my current HCD layout, I'm again geographically limited to relatively narrow curves, but I try to manipulate track and scenery to make it feel more open.



At the inevitable turn back, I tried to create a scene that was busy, yet plausible, in order to mask the sharp tail chasing curve.  And by using a few scenic elements, the road and railroad bridges, for instance, I break the scene up into bite sized pieces to discourage the viewer from just seeing the trains looping back on themselves.



And even though there's less than 7 feet to work with, I worked in another long sweep to give more an an illusion of distance, in photos as well as in person.


So keep in mind that designing a track plan requires you to think about:

• What kind of scenery will you need to build?
• What kind of traffic would your chosen railroad be prone to run?  (Don't build for double stacks and auto racks if you're not going to run them)
• How much actual room do you have where you need your sharpest turn?  (Probably the most important consideration)
• How generous can you make the other scenes to promote the illusion of broad curves and long distances?  (If your visitor is "oohing and aahing" at a well crafted canyon with a broad curve following a swift river, they are less inclined to notice that the pilot of your Big Boy barely scrapes through the tunnel portal at one end where it has to loop around)
• What kind of tricks will you have at your disposal to further that illusion? (vignettes, scenic blocks, building flats, tunnels, etc)
• What are the key viewing angles and must-have photo locations that you want to work into the plan?  (This is something that frequently gets lost on layouts that try too hard to adhere to reality with scale width parking spaces and a street grid on right angles to the table edge.)

And answer all of this before you start whimpering about how snug your turn is for your 89' high cube autoracks with body mount couplers being pulled by an SD40-2 with 20 feet of porches on each end...

Then, make the necessary compromises you need to make to have a layout design that checks most of your boxes. 

Good luck with the pencil pushing.  For me that's always the best part.
Lee

[greenwizard88]

Honestly it depends on what you're planning on running. If you think you can keep yourself to 4-axel engines and short freight cars with truck mounted couplers, 8.5" or even less for a minimum radius is just fine. Of course, larger always looks better, but needs must and all that.

For an absolute minimum radius, I'd go with 9.75", that's the minimum that Kato uses, or 11" if you want to be able to run a Kato Big Boy.

If you look at manufacturers, most of them go with a 9.75" minimum (scale trains, BLI, etc). If you don't want to worry about minimum radiuii, I'd suggest a 12" radius, at least, as I can't think of anything that wouldn't run on a 12" radius curve.

Having said all that, a Big Boy on a 9.75" curve just isn't going to look right, even if technically it can navigate it.

I personally used Kato 282mm as my minimum radius, since most manufacturers seem to have standardized on supporting T-Trak (that's the minimum radius for T-Trak) and I never had issues running 4-8-4 and 4-4-4-4 steam engines. My mainline is about a 16" radius, for appearances, but that's not minimum radius

[Rossford Yard]

Put me in the 15" minimum camp for any siding, and at least 18" radius for the mains, more preferred.

For any radius, easements help the aesthetics of trains running through.  Turnouts provide those naturally (Atlas 55 has 30" radius through the frog, I think).  For other curves, layout the 18" radius to hit the inside rail, not center to center, so the curve gradually goes into it's radius.  Putting small shims (business card height, or a bit more) gives them some super elevation and is easy to do, as well.

I did a layout once where a 180 deg turnback curve was partially visible and partially hidden in a tunnel, so I widened it where visible and made it a bit tighter where it wasn't.  Bad move as the locos and trains slowed down when they hit the tighter turn, even if the rest of the train was visible, so there was an unexplained and visually jarring running characteristic which I never liked.

As to tail tracks for switch leads, I recommend a slight uphill gradient, and being as straight as possible.  Pushing N Scale cars around a curve to switch usually leads to the first car being pushed up and off the rails if going 90 deg. or over.  If curved, a slight superelevation helps keep them on the track a bit better.  While a switch lead ought to be as long as your longest AD track, I also find that switching much over 15-16 cars adds to problems, even if you run really slow.  Therefore, a lead that allows you to only switch half your cut length is a bit unprotypical, but in the end, probably makes switching more enjoyable.

[nickelplate759]

Put me in the 15" minimum camp for any siding, and at least 18" radius for the mains, more preferred.

For any radius, easements help the aesthetics of trains running through.  Turnouts provide those naturally (Atlas 55 has 30" radius through the frog, I think).  For other curves, layout the 18" radius to hit the inside rail, not center to center, so the curve gradually goes into it's radius.  Putting small shims (business card height, or a bit more) gives them some super elevation and is easy to do, as well.

I did a layout once where a 180 deg turnback curve was partially visible and partially hidden in a tunnel, so I widened it where visible and made it a bit tighter where it wasn't.  Bad move as the locos and trains slowed down when they hit the tighter turn, even if the rest of the train was visible, so there was an unexplained and visually jarring running characteristic which I never liked.

As to tail tracks for switch leads, I recommend a slight uphill gradient, and being as straight as possible.  Pushing N Scale cars around a curve to switch usually leads to the first car being pushed up and off the rails if going 90 deg. or over.  If curved, a slight superelevation helps keep them on the track a bit better.  While a switch lead ought to be as long as your longest AD track, I also find that switching much over 15-16 cars adds to problems, even if you run really slow.  Therefore, a lead that allows you to only switch half your cut length is a bit unprotypical, but in the end, probably makes switching more enjoyable.

For longer rollingstock, I'd say easements are very, very important, not just for esthetics but also for functionality.  I think you are better off with easements and 16" radius than 18" radius without easements, for example.

[crrcoal]

Brian are you able to post a sketch of what you are planning? It might help with others giving you their feedback.

[randgust]

There's two very different ways to look at it....

a)  what works in N scale as a practical minimum?   I've gotten away with 11", although I've had to modify a brass 4-8-4, and several intermodal flats with body-mount couplers.   

b)  What looks good?   I go with the 15" crowd, that's my visible main line minimum.   But I'm also stuffed in a small basement train room.  And 15" looks a whole lot better viewing from the INSIDE than the OUTSIDE of a curve.

The typical minimum radius in the real world was typically 14-degree, used on wye tracks on a lot of railroads for steam and train turning.  That's 410' radius or 30.75 inches.  So that puts things into perspective, and a PRR K4 still couldn't back around it.    The sharpest I've ever seen in the field (High Falls Curve in WV) that a passenger train actually negotiates (West Virginia Central) is around 33 degrees, I measure 230' radius, or 17 1/4 inches in N.   If you've got a railroad full of 20-degree curves your're cursed, and 12-degree curves knocks you down to around 15mph.

So while I use sharper curves, even you guys with basement-sized layouts are pushing it, there's no moral high (or wide) ground here.  We're all wrong.