Based on my use of layout sections that had 9.75" radius and 11" radius curves, I will share these thoughts: 1. Quick changes in curve radius are more risky that the tight radius curve itself. So if you connect a 9.75" curve directly to straight track, that joint will be a problem point. Many advise using easements where the first part of a curve has a less tight radius. 2. If you have any changes in track elevation, such as an inclined section going between lower and higher elevation layout sections which themselves are flat, the grade transitions will kill. With a layout as small as yours, I would keep all the track completely flat. 3. 11" radius is much better than 9.75" - this is a huge difference. 4. If you couple together 2 pieces of rolling stock, where 1 has a body-mounted coupler and the other has a truck-mounted coupler, that will be a problem. Many locos have body-mounted couplers. Since most of my rolling stock has truck-mounted couplers, I created "adapter cars" to sit directly behind them, with a body-mounted coupler and truck-mounted coupler at its two ends. 5. The layout diagram posted by jdetray shows that a loop with 11" curves will *barely* fit on a 2 feet by 4 feet board. But then you are stuck at the outside of the board, which is boring, and rolling stock that cannot go tighter than 11" curves may have problems going to the interior. It will be much better if you can make your layout just 4 inches deeper (28 inches instead of 24), and then use 11" curves as much as possible. 6. Many of us love steam engines. Those little pilot and trailing trucks help the prototype stay on the tracks, but these are just a decorative nuisance for N scale steam engines. You may get additional aggravation with these. 7. High quality turnouts are a must. I really like the Peco turnouts (I do not use Kato Unitrack).
I know these statements are completely contradictory, but I had to like them both. Much depends on what kind of equipment you want to run, and much depends on how much time and patience you have for building and maintaining exceptional track. And, yes, few of us have such a luxury of space that we can have everything we want. I'd also like to put in a word for a more complex set of standards. There's a lot to be said for maintaining a set of standards which say, main lines must be this good, but yard tracks and sidings only have to meet this other standard. This makes many things possible--fine passenger running on the main yet more freight action than could otherwise be crammed in if that mainline standard was applied everywhere. Armstrong talks about that, if I remember correctly, in his excellent book, and I think it's an important thing to keep in mind. Yards don't see passenger cars switched and high speed running. That makes a big difference,
The simple answer to the OP's question is yes. Most engines made recommend a minimum of 12" radius for modern equipment and 9.75" radius for steam engines, in general. A good "medium range radius" is 14"/15", and a good minimum radius is 12". Either of those will accommodate any loco or train config you choose to run, not withstanding absolute realism. Just a small point - I can run (without issue) a Kato GEVO ES4400AC engine on my wife's 8" radius under the tree track. Sure, it doesn't look realistic BUT it does run and stay on the rails.
If a loop is what you want, and you can't go bigger than 2'x4', there is still plenty you can do with that space. I have been getting by with a 2'x4' for about 5 years now- it's been taken apart and put back together more than once, but it's survived several small apartments so it's got that going for it and it scratches the itch when I want to see my collection move instead of just looking pretty. Now that I have more space I'm working on upgrading to a 3'x7' hollow door, but I'm not done with the compact plan just yet either. I don't own any Harriman cars, so I can't speak to how well they take 9-3/4" curves, but a 4-6-0 will do just fine on them. Most 4-axle diesels and smaller steam will look okay on that radius, and 40-50' cars will too. Opinions will of course vary on that point, but I consider the outer rail rule to be good enough. Once you go larger than 4 axle diesels or small steam, though, results will vary. Some things that seem like they should handle the curves okay won't be able to, and others that you take one look at and think "no way in heck" will glide happily around those tight corners all day long. Case in point: I have an Atlas Trainmaster that pops its truck contacts out on the compact layout, but my married pair of BLI Centipedes won't even flinch. This is an old picture from before I painted the board (2" insulation foam over 1/2" plywood), but this is what ended up as my final track plan... with some minor substitutions; I didn't have enough longer sections at the time, so I plugged in shorter ones until I could replace them. I had trouble with the #4 Unitrack switches (all the points needed to be filed- I gather that's a common issue), but after solving that it works great. You can just ignore the improvised HO test stand in the middle- I've since put a scenery divider in there to break up the space into two different scenes. The inspiration for the basic plan, including the kidney bean shape, came from David K. Smith's old site.
If you want to run short locos and 40' rolling stock, this isn't a concern. You can go 9.75" and no big deal. If you want to run 85' passenger cars, 89' flats and/or autoracks and large steam or large modern locos, try as much as you can NOT to go below 18" if you want to be happy, and by all means do not go below 15."
Frankly, and these convoluted discussions give me the heeby-jeebies, everything, including 'standards' are a guide. People should experiment and experience. What satisfies as looking ok on sharp curves depends on the viewer. Newbs dont often see the aesthetics of gentle rolling smooth curve lines that pro's or experienced hobbyists do. Getting your ideas together on what equipment you want to operate, how and complexity of numbers, then testing track portions and formations (like siding lengths etc.) will give better ideas of what you can achieve in a given space. Dave PS- my test 4x2 layout design also looks like 'silentargus' one. It isnt a long car runner, but as an over and under it is a test bed for 6 axle locos and car rolling abilities.
Shortliner13, Listen to what nd-rails said ... experiment and ascertain for yourself how small a radius you can go based on what you want and like. For those who say you "if you want to enjoy this hobby, don't go below 15" radii" then there are a LOT of people in this hobby who apparently mustn't/don't enjoy it! From memory, I don't recall ever seeing any manufacturer recommend/suggest a minimum radius greater than 12" (N Scale) for their products - none. Apparently they (the manufacturers) don't want anyone enjoying this hobby either. I had an N Scale layout on which I ran Kato GEVO ES440AC engines, Kato Autoracks and Kato Intermodal cars, amongst others, and the maximum radius I had (due to space limitations) was 15" with a minimum radius of 11", there abouts, and I had absolutely NO problems what so ever. Heck, I even ran (just for fun) my GEVO on my wife's "under the tree N Scale" with no issue either and that only has 8" (give or take) radii curves. Sure it didn't look prototypically real BUT it worked and, was for me, fun to watch something that strictly speaking shouldn't have worked. I also agree with nd-rails where "standards" are concerned but will go one step further ... standards are nothing more than a guide line, a suggestion based on realism and personal preference by those who created them. While those "standards" may be okay for them (and some others) they may not apply to you or what you want to do. The ONLY standard/s that will apply to YOUR layout will be YOURS. Those standards will be derived from what you want and from what you believe works for you and gives you the most satisfaction. Don't let some one else force or push their standards on you as I am sure that what they (or I) do/have is going to be different to what you do and/or have. The bottom line Shortliner is this - it is YOUR layout and the ONLY person who has to be happy with it is YOU, no one else. Forget about standards and this or that and do what works for you based on what you have to work with. You implied that you only have a space of 2' X 4' to work with so you are going to be greatly restricted as to the max radius you can go anyway which will be 11" allowing for a 1" "safe zone between your track and the edge of your bench work. Even with 11" radius, you could run the majority of trains, if not all of them, and have plenty of enjoyment doing so.
I've done a lot of "don't do its" in my lifetime. Some worked out well, others didn't. The best way to learn is by someone else's mistakes, but if everyone sticks to the tried and true methods.....no one will make a mistake!! Or learn!!
Didn't the OP say 2'x4' sectional, not 2'x4' total area? If so, 2'x4' sectional does not impose an 11" radius limit.
Point353, Yep, your right - he did say 2' X 4' sectional. Whether or not the OP is restricted will depend on how he configures the sections and how many he has or is considering using. Four 2' x 4' sections end to end would still restrict him to 11" radii. Four of those sections forming an 8' x 4' is another matter and obviously wont restrict him to an 11" radius. At the end of the day though, he asked if he could go smaller than 18" radius and the answer is simply yes, and do it comfortably as far down as 9.75" radius, depending on what engines and rolling stock he wants and how much realism he wants. Nothing is set in stone.
