The New York harbor float terminals such as the Harlem Transfer used 90’ and 104’ concentric curves. They worked them with boxcabs and GE 44 tonners. For an ISL using maximum 40’ rolling stock you will be fine at 15". Just don’t try to push modern six axle diesels and auto-racks around them.
As I just posted in a thread on the General forum. Read:
Another good complementary reference is the Layout Design SIG’s Curve-Radius-Rules-of-Thumb. This distinguishes between what radii might be made to mostly work, what will work well all of the time, and what looks good – all based on car length.
I would not go below 18" in HO. but as long as your cars are 40’, this looks fine and not toylike at all. Flatcars can be a bit longer without looking toylike. At 50’ cars, they still perform fine but the illusion of space starts to diminish on the 18" radius curves (why I got rid of almost all my larger cars). Now engines are another mater and small ones look fine like my Proto 0-6-0’s and 0-8-0’s or my early diesels. Also of note they looked fine on outside curves too and with the space I had at the time I could have picked up to a 36" radius but did not because of what I was running. If you are running autoracks, they may run on 22" but look weird on anything smaller than 42" though some find the ok at 39".
It’s your layout and you don’t really need our validation or discussion to put in sharp curves if you know your rolling stock will operate reliably on your planned curves.
As always, make sure your minimum radius will allow reliable operation for all your equipment.
when i started a layout about 5 years ago in an empty bedroom, i built a simple pt-to-pt with a 15" loop at one end (like John Allen’s original layout). I wanted to build something and didn’t want to get hung up in “analysis paralysis”. I decided to recognize its limitation and bought some small switchers (a Rdg B8). A Rdg I-10 i really like is on the shelf. I hand laid turnouts. I’m experimented with a turntable and built an elevator. I recently completed a signalling system with Arduinos. All this is easier with a small layout.
I have plans to expand the loop to something bigger if it becomes a problem. I’d also like to re-lay a turnout as a curved turnout. I’m also a member of the Pacific Southern club.
its taken me a few years, but rather than over analyze, I have something I can operate and enjoy today.
The post was not really to ask any real question. Just thinking about the subliminal message we all put out to avoid curves like the plague. I myself have seen what people say and was concerned about all of the things that might happen. I made the post because I see other threads about radii, but none talking about when it’s really ok. If anything, I was trying to just get a stamp of approval for the ideas in my head.
Like has been said, all that really matters is if your equipment runs on it, and it looks good to your eye, then you’re good to go.
The big issue, as I’ve learned, pertains to expandability. As others have mentioned, if you keep your equipment small, you’ll be fine, but you will be locked in. Running larger equipment will probably require you to redo your track. And this is what standards are usually designed to address, whether in model railroading or anything else - that middle-of-the-road balance between reliability, desirability and practicality.
But even such tight curves are to be found in prototypical operation. In researching my layout, I came across some images of a wye in operation on my prototype, the Arcade and Attica, that is extremely tight by today’s standards (it’s about a 200ft radius), but they use only GE 44-tonners (for revenue - they do run a 2-8-0 on excursions). So your curve and equipment choices are borne out in prototype.
LION decided that all curves on layout of him would be 26" or greater. So smart LION builded table with 24" curves. Now all I would need to do was lay the track matching the curve and it would be at least 26" (Right?) The next track would be 28", the third would be 30" and the fourth track would be 32" radius. (After all subway layout of LION does have four track mane lions.
Well it WAS a good theory, but some of my curves are still way sharper than I planned for.
Fortunately, subway cars are only 50’ long and so can transverse my surves whatever they are. : )
YOU on the udder hand can milk it for all it is worth, Industrial and switching yards pay no attention to minimum radius. If you engine and car can make the curve, all well and good. Even if your engine cannot make that last curve into a wearhouse, a couple of reach cars will work just fine and will add interest to your opperation.
IMO, any radius is fine as long as it operates. If you’re trying to pull off a realistic look, then the surrounding scenery should dictate the need for sharp radius.
Wharf’s, urban areas, fitting between a tunnel and a stream, etc, all require the prototype to make things a bit tighter than if they had gobs of flat plywood to work with. Logging trains, coal trains, ore trains tend to have to sneak their way around physical barriers, as do any cars being switched in many urban areas.
