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Minimum Track Radius

Ronnie asks:

“In HO is there a minimum acceptable track radius based on various car or loco lengths? My main concern right now is 2 axle 4 wheel truck diesels compared to 3 axle 6 wheel truck diesels. Thanks for any help.”

Please post any suggestions directly underneath this post.

4 Responses to Minimum Track Radius

  • Jim Junod says:

    Two axle units can handle an 18 inch radius but three axle units operate best on a minimun 22 inch radius. The best practice is to use a 22 inch radius or twenty four inch radius.

  • Ken Holbrook says:

    Hey Ronnie, that’s a great question. Most locomotive manufacturers suggest a minimum of an 18” radius for most 4 axle locos. Some 6 axle locomotives do fine on an 18” radius though many do not. I’ve actually had to remove the chassis of a BLI SD-35 6 axle loco to modify the minimum turn radius with my Dremel tool. It’s not for the faint of heart, that’s for sure. But if done correctly you can get a 6- axle loco to navigate a 16” radius with ease! But if you want to stick with out of the box, use 18” as a baseline and you can’t go wrong.

  • Frank B says:

    A trick that is used by some manufacturers on long steam locos, is to remove the flanges on the middle driving wheels. This allows the loco to go around tighter curves.

  • David Stokes says:

    How timely
    I have two three axle locos that have refused to behave on curves that never bothered thenm before. The radius was 24 iches.
    I have been advised by one of my NMRA mentors that such locos need 30″ minimum radius to be happy. He also said that some manufacturers make the central axle on 3 axle bogies very tight. He uses 14mm as his back to back, he eases the axle mounts so that they have easy slide slip so that they follow the rail. Good luck with 18″ – the loco modifications as you say “are not for the faint hearted”.

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