Let's talk radii

[Ed Kapuscinski]

I'm working on a plan for the next phase of Windsor St, and I'm curious what folks thoughts are on mainline curve radius.

What do you consider an appropriate mainline radius?

18"? 22"? 24"?

What are your thoughts?

[Mark5]

I am currently in the 22" camp

[basementcalling]

18 minimum. If you can go 24, do it. That's the NTRAK main minimum and it looks damn good compared to 18.

[draskouasshat]

I'll be going 24"or larger for my curves. I've had to redesign my plan a few times so far.

Adam Draskovich

[seusscaboose]

Depends if it's in view

And how much room you have

In your case, you got plenty of room for big curves

I vote for big

[Cajonpassfan]

The bigger the better, BUT it's all a series of trade offs. You open up the radius here, and have to squeeze something else there. I have 18" minimum, but I model 1950, with a lot of 40' cars and first generation diesels, and even then, I have a number of larger radius curves where possible, up to 54". Modern era, I wouldn't go under 22", and more where possible. But again, there are a lot of variables and you need to come up with an optimal mix that's right for you.
Best, Otto K.

[jagged ben]

Consider grades too.   

I'd probably settle on something like 18" in flat hidden or staging areas, but I'd increase that by 3" for every 1% of grade. 

Visible areas I would do 24".

To each his own, obviously, but I don't think I'd want to build a layout if I couldn't manage that, given the long trains I'd want to run.

[Santa Fe Guy]

What every body else says. I had to go as low as 161/2 inches to fit in another peninsular so for me it was worth the compromise. I do not run any cars over 60ft however.
Rod.

[nkalanaga]

My standard is 18 inches, but I have one 16.5 inch curve on a passing track.  85 ft passenger cars and 89 ft flatcars with body mounted couplers take it just fine, but I wouldn't go much below that.  If you have to use sharper curves, I'd recommend keeping the truck mounted couplers, or make sure you have plenty of truck and coupler swing.  It's also important to watch the car combinations.  Just like on the prototype, long and short cars with body mounted couplers don't mix well on sharp curves.  Don't couple the ore car to the autorack!

That said, I'd go with the biggest you can fit.  If you have room for 36 inch curves you will be in the prototype range for sharp mainline curves, and shouldn't have trouble with anything, regardless of couplers, except maybe extreme length/overhang mismatches.  I wouldn't waste space going wider than that, unless you're trying to model a particular location to exact scale.

[mmagliaro]

After having lived with 18" minimums for years now, I would never ever go back to anything tighter.
And... if you have room, I would definitely go for 22 or 24.  You will have to decide how much you might have to give up
in additional trackwork, scenery, or space for structures by going broader.  There's no question that everything just
runs easier and derails less when you get up around 18".  And with some of the long steam, I have even occasionally run
into issues on 18", so I wish I had the room to go broader.

You may not be running big ol' steam locomotives, but I still say the improvement in ease of use is worth it.

As for looks:
I've got some 22 and 24, and some 18 on my layout.
The trains definitely look better on the 22 and 24.  Those are the curves where the 80' passenger cars finally stop looking
"broken in half".

[Catt]

I used 18" radius HO snap track to layout the curves on my Grande Valley rebuild because I could not find the 22" radius track.Of course as soon as I have roadbed and PECO flex laid I find the 22". I would never go back to a smaller radius curve (at least not on the mainline).

Auto racks are still silly looking critters on 18" but anything smaller I simply would not run them.

[Philip H]

I think it comes down to a couple of basic things - in this particular order:

• How much space do you have?  As @seusscaboose already noted you've got plenty of room, and N scale allows for the maximizing of that room.
• what sort of operations will you be adding when you expand? mainline running or industrial switching?  Both - and everything in between - can be enhances by the right choice of radius.
• Whats your era?  this gets at cars most likely to be seen and car lengths, which influences minimum radius as well as siding length.

[brokemoto]

When considering curve radii, I always go back to what I learned in my HO days.  Everything that I read back then put curve radii into three categories:

Sharp-23 inches, or less

Conventional-24 to 29 inches

Broad-30 inches, or better.

In N scale this works out to

Sharp-12,52 inches, or less

Conventional-13,08 to 15,79 inches

Broad-16.33 inches or better.

The "Standard" sharp curve back in the HO days was 18 inches, which works out to 9,79 inches in N

The alleged "conventional" SNAP-TRAK (@) curve of 22 inches, really fell into the upper-middle of the "sharp" category.  Twenty Two inches in HO works out to 11,98 inches in N.


The advice of the time (back in my HO days, a majority of the modellers were still running mostly steam) dictated that you could operate anything up to a 2-6-2 or
4-6-0 on sharp curves.   Conventional curves allowed anything up to a 4-6-2 or 2-8-2.   You could run anything on a broad curve.  There was something thrown in about the diesels:  you could operate small and average diesels on sharp curves and larger on conventional.   If you wanted to run shorty passenger cars, you needed conventional curves.  Full length passenger cars could operate on broad.


The exception to the above was nineteenth century and trolley equipment.  All of that was supposed to be able to operate on sharp curves.

In HO, I was "modelling" a fictitious SP secondary on the SF Peninsula in the mid-1950s, so all that I was running were Pacifics, Atlantics, Ten Wheelers, Moguls, Mikados, Consolidateds and six wheel switchers, anyhow (Varney and Roundhouse had many models back then which were based on SP prototypes).   I used Athearn "Blue Box" passenger equipment, which was slightly shorter than the prototypes on which they were based.  Thus, I got away with "conventional" 24 inch main line curves.


In all honesty, the large steam and full size passenger cars did not look quite right on thirty inch curves.   At thirty three, or better, it looked allright.  HO 33 inches works out to 17,96 in N.

As I recall, you are running more modern equipment:  longer rolling stock, longer SD-whatevers and the larger GEs.  Thus, while it is likely that you might get away with the eighteen inches, the larger radii would look much better.  Twenty two inches in N works out to 40,41 inches in HO; 24 inches in N to 44,09.   If you can go to 24 inches, it would be better, of course, but you will get away with the eighteen.

On my non-historic railroad, I run 0-6-0s, ten wheelers, eight wheelers, moguls and consolidateds.  The diesels are first generation four axles.  The freight rolling stock is no longer than fifty scale feet.  The passenger equipment is B-mann sixty-five foot shorty passenger cars or WOT and MT seventy foot head end cars.  Thus, I get away with the Kato 13,75 inch curves on the main line.  I would get away with the Kato #4s, except that they are so horrible that I went to the #6s.  That put an end to point and frog picking.

To be sure, if you scaled these standards out to 1:1, even the curves in the "broad" category would be too sharp for anything other than industrial or trolley trackage.

[randgust]

I'm running parallel two-track mains of 13/15 as standard.    My own observations:

1)  You're pushing it - hard - on any brass steam.   I had to modify my Hallmark Northern to even run 15".
2)  It looks a whole lot better the higher the eye view is, (I use 52" table height)  and also if you are on the INSIDE, rather than the outside of the curve.  As I only have one curve of that radius visible from the outside view, I think its a factor in the visual.  On my layout you're looking from the inside of the curve out for 360 degrees of curvature over eight feet.  Overhang is more objectionable looking from the outside where you can see the rails under the center of the cars.  I've got a 15-car piggyback as my worst-case scenario.
3)  If you've got a lot of body-mounts, long cars, and long trains (I run 30 car trains) you're pushing the stringline factor on that combination.  I'm OK with truck mounts though.

Performance factors on hidden track:  I go down as tight as 12" on one tight reverse loop, works fine.   You can run through curves it still looks relatively absurd on with most things with fewer problems than you'd think.

I came from HO with 18" curves stuck on nothing bigger than a 4x8 so a 15" curve seemed like heaven to me then in N.   But I also have my little portable logging modules than use 9" on about everything, so that 13/15 still looks good by comparison.

I also tend to superelevate the curves and run relatively slowly, or so I've been told.  It's not a big layout, I just kinda push the limit on the size of equipment and length of trains I operate.  Without demolition, I don't have any more space, I'd have to go to Z or something.

[jpwisc]

I was planning on broader corners, but space restrictions pushed me to my 22" minimum. I like how my 36" radii look much more, but I'll make this work.