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Thread: Turn Radius

  1. Default Turn Radius

    What's the recommended turn radius for HO scale? Looking to design a shelf layout and hopin to get a lower deck system.

  2. #2


    Depends a lot of what type engine and equipment you'll be running. A Big-Boy or DD40X is gonna need a lot of room. A small switcher doesn't need much. 24" is used as a good standard now days.

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  3. Default

    Obviously, the greater the radius of the turn the easier time you will have with engines and rolling stock negotiating the curve. The problem is that most folks, including yours truly don't have the room for very large radius curves. (In point of fact, model railroad curve radii don't come close to prototype curves except for very tight branch lines or logging railroads!)

    "Standard" HO scale sectional track commonly comes in 18-inch, 22-inch, and even 15-inch curves. Flex-track can, of course, be bent to form whatever curve you want. But it is somewhat more difficult to keep a consistant radius. You can obtain larger radius sectional track made by Shinohara, which IIRC, you can obtain through Walthers. In my own instance, because I want to run passenger trains, I had to compromise by using 20-inch radius Shinohara on my main lines and 18-inch Atlas snap track for tighter curves. Shinohara makes sectional track in sizes from 16-inch to 30-odd inches.

  4. Default

    So if I did a 4'x8' layout, using the 22" radius would that work for a turn?

  5. Default

    Quote Originally Posted by TucsonRails View Post
    So if I did a 4'x8' layout, using the 22" radius would that work for a turn?
    We don't know. As the first reply stated, it depends. If you run a long modern diesel, some will negotiate an 18" radius while some won't. So, you need to match your locomotive and longest pair of cars with the smallest curve that rolling combo will take.

    A safe bet for almost all non-brass locomotives is 22" radius in HO. However, not all of them will work on that small a radius. A 2-10-4 steamer won't, plastic or brass, and the example of a DDX-40 probably won't either. Neither will any HO passenger car longer than about 75 scale feet that also has diaphragms.

  6. Default

    Quote Originally Posted by TucsonRails View Post
    What's the recommended turn radius for HO scale? Looking to design a shelf layout and hopin to get a lower deck system.
    If you want a continuously running shelf layout, you can run small 4 wheeled engines and short rolling stock which can negotiate very small curves. This is a test layout with a 6 inch radius circle...

    It is possible to fit a continuously running HO gauge oval track layout onto a shelf with a depth of only16 inches.

    Last edited by tooter; 07-02-2011 at 12:14 AM.

  7. #7
    Join Date
    Oct 2005
    Mile 7.5 Laggan sub, Calgary, Great White north


    A 24" radius will run almost anything...a 22" might have some difficulty with 80'+ equipment, like long passenger and intermodal cars. If you're only having boxcars and whatnot with 4 and small 6 axle power, 22" would work. I've designed my N scale railway to have 18" curves, that will run anything - equivalent to about 36" in HO.
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  8. Default

    It depends on your layout...

    If you want to run centerbeams, autoracks, 89' flats, or any really long car down your track, you want a 24" radius.

    I am designing a switching layout which at minimum is 22" (mainly 24). It can take the above, but the mainline's biggest car is a Tri-Rail Bombardier Car which may be a bit tight.

    Though I am not running Tri-Rail, if I really wanted, I would probably need a larger radius.

    But if you're doing like a coal layout then you can get away with 22".
    --Tolga Connoisseur of all things FEC

  9. Default

    It really depends on what you want to run. THe more modern the locos and RR cars are, the larger radius you will need.

    If you are going to run small steam or GP-anything and some SD-somethings {up to SD-50}, you can get away with 18"R curves.

    Bigger than that and you will really need bigger radii. THat would include passenger cars over 65-ish scale feet long in HO as well.

    Atlas has come out with new "snap switches" that have 22"R divergent routes so you COULD, on a "plywood prairie" have an outside 24"R curve oval and switches matching into an inner circle/oval of 22"R curves IF you have an external support system for your table {such as the 4x8 recessed into a 2x4 framework}, making it bigger than just 48" wide, allowing for clearance as the locos go around, OR if you do a 5'x9' "Plywood prairie they will easily fit.

    Even then, the larger steamers and modern longer diesels and longer RR cars {such as auto racks, deep well intermodals and anything over 65 scale feet} still may not like your 22"R and 24"R curves.
    HO and N

    Just my thoughts, ideas, opinions and experiences. Others may vary

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  10. Default

    Well thanks for the advice. I'm sure I'll end up running longer engines and rolling stock, so I'll rethink my layout. Thanks again!

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