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What Size Should The Curves Be On My Model Railroad?

At 84 years young, Jim is planning his first layout and is hoping readers can give him some advice:

“I am 84 years old and about to start my first ever HO layout and admit to being pretty dumb about model railroads. My available size will be 42 inches by 13 feet with only one long side that is not against the walls. I want two loops. One for a freight train and the other for a passenger train. The outside loop can be the normal 18 inch style but the inside loop can not be that wide but in fact only 15 inch. I know that short rolling stock can easily operate on either size but not passenger models with the long cars. I really wish I had an AM Track passenger train but I hear they only come in long cars. Is there such a thing as short passenger cars that are short enough to operate on the 15 inch long line? I thank anyone who might be able to help me. Thanks.”

7 Responses to What Size Should The Curves Be On My Model Railroad?

  • Don Kaduncsays:

    Switch to single track in the curves.

  • Rudy Blawsays:

    20″ radius and certainly 18″ radius will be too tight for many modern passenger cars. On the layout I’m building, I had to replace a curved switch to a 24″ radius because one specific car (Walthers UP First Edition Dome Diner) had a ladder next to the truck (bogie) preventing the truck from swinging out far enough, resulting in derailment of the car. A similar problem I had with an El Capitan Diner which has 3 axle trucks. I had to modify the bottom of the car to make it go though the 24″ radius.
    Best bet for passenger cars on tight turns is to model the Old West (19th Century) or Europe in the early 20th century. Early European cars had two axles. You may have to look for vintage equipment from Fleischmann (DC) or Maerklin (AC).

  • Kevin Chingsays:

    Hi Jim
    You may be able to get some old time passenger cars that are short I have some on my layout they are about the same size as a 50ft box car i am not sure who made them as i picked them up second hand a few years back, I run them with a 2-6-0 steam loco and they look ok.

  • Dale Arendssays:

    A lot depends on the era you’re modelling. Modern passenger cars are generally long and while most should handle 18 inch radius, they won’t look right. If you intend on the early to mid part of the 20th century, say 1920-1960, the time-appropriate passenger cars were shorter – often in the 60-65 foot range rather than the current 72-85 foot sizes.

    Don’s suggestion of single-track in the curves is a good one, not only for the rolling stock but would add some complexity and interest to operations.

  • Bobsays:

    You might want to consider a “bump out” at the ends of your loops. They wouldn’t need to be much bigger than 8 inches to allow 24″ radius curves. Most HO should run well on 24″ curves.

    You might also consider a gauntlet track (see some on youtube) for the curves. It would require block controls for unattended loop running but so would switches.

    Of course you could set the loops at different levels or double deck just the curves without too much fuss. Lots of possibilities for creating interest using different or changing elevations.

  • Tim Morloksays:

    Hi Jim, If you want to stay with the two loop plan, you could use the 18″ radii on both loops by elevating the back of the outside loop into a dog bone shape. Then run the inside loop under and behind this raised portion.
    __ __________________________ __
    / \ / \ / \
    / X_____raised _____track_________X \
    / / \ \
    l l l l
    \ \ / /
    \ \_____________________________/ /

  • Tim Morloksays:

    sorry about the drawing.

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