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Minimum Radius for Trains

Tyson used the link below to post this question to readers:

“I am new to model trains.What is the minimum radius i should be using on the main lines for n scale and what is the minimum distance i need to keep from the track to the edge of the layout. My layout size is 3 x 6.”

11 Responses to Minimum Radius for Trains

  • donj1044says:

    You really do not have much space for a train layout, try a small circle. Get short engines and rolling stock. try to find more room for a layout when you can GOOD LUCK

  • Bruce Scottsays:

    The minimum radius of curves you select depends on many variables which include the era and theme along with the equipment being run.
    Running modern passenger or freight, with 89″ flat cars, full-size passenger cars or even the steam era running big articulated locomotives you will need broad curves for appearance and proper operation.
    If you are modeling the early 1900’s to mid-1900’s equipment was much smaller curves. Either way, equipment especially locomotive instructions will give a recommended minimum radius for curves.

    Usually, we want to run the broadest curves that we can comfortably fit on a table however, there has to be a compromise. Taking this into consideration, you don’t want to run track to close to the edge of the table for two major reasons. 1. To avoid equipment falling off the table and 2. Appearance, the inability to model (decorate) from the track to the edge of the table. I’ve read 2″ inches is the minimum for HO, however, I would recommend doubling this. With N scale this will give you plenty of space to address both these issues.
    Hope this helps.

  • Bill Howesays:

    Minimum radius is determined by your equipment and what you want it to look like. Most if not all your rolling stock will get through a 9″ radius. How it looks is another matter. 40′ box cars and small locos may look ok, longer cars and bigger locos will look toy like as their middle will be inside the inner track as they negotiate the curves. They will make it through but they won’t look prototypical. If all you want to do is run trains and your not worried about the “look” then use 9 inch radius, for better looking stick to 12″ or 16″.


  • mikesays:

    you don’t say what scale you are using, but just google “minimum radius for model train track”
    I use N Scale and it is generally accespted that 9 3/4″ is the minimum. What type of rolling stock is a consideration, freight or longer passenger cars with make a difference. longer cars require more radius.

  • I can only speak from experience but I have a coffee table layout and I made my curves on each end 30cm radius. The layout was only 60cm (approx. 2ft) wide by 120cm (approx. 4ft) long so that was the maximum radius that it would allow. I had no problems with it as I did not have any engines or rolling stock that were extreme in length. I also had the rails as close to the edge as possible to maximise the amount of space I had. In some areas it was as close as 5cm. Bare in mind that this was an enclosed layout, so there was no possibility of the train falling of the layout, in the event of a derailment. You could do a back board with painted scenery or relief buildings on it all the way around your 3×6 layout to create the same effect.

  • David Stokessays:


    Please, please do not spend money on models until you have done the research – too many mistakes made in ignorance at the beginning means you’ll drop out of our hobby too early to really enjoy it and waste a lot of money.

  • Dale Arendssays:

    That depends on the length of the cars and locomotives you intend to run. A small 4-4-0 steam loco can handle a sharper radius than an 2-10-0 loco. Similarly, 40-foot freight cars can take tighter curves than an 85-foot passenger car. So, if you keep track at least 2 inches from the edge (closer is ok if you put up a clear fascia high enough to prevent falls) then you have a maximum of 16 inches. As for minimum, if you keep to shorter cars and small steam or 4-axel diesels, you should be able to get away with a 9 inch minimum radius. Going down to 7 or 8 inches may be possible but I wouldn’t recommend it unless necessary.

  • Briansays:

    Hello Tyson, There are several sites which you can browse regarding minimum radii. However, I’ve found that 12″-14″ minimum if you wish to have a realistic curve setting, more is better. As for the minimum distance from the edge of the baseboard, I’d try to leave at least 4″-6″, just in case you have a derailment, you don’t want to see your locomotives and trains falling onto the floor, not good. I hope you enjoy the hobby, it’s grand especially during the dark winter days. If you want to plan your layout try the ‘Templot’ track program, just type ‘Templot’ into your browser. It can be daunting at the start, but there are loads of video’s available on-line to help you, even on ‘YouTube’. KR Brian

  • Timsays:

    Mate, you’ve got heaps of room if you keep trains short and run short locos. Don’t let people tell you how big your layout needs to be. Check out carendt.com. Lots of small detail scenes will make it interesting. Don’t forget you are starting out and enjoy the little boo boos and learning along the way. How close you get to the edge can be found out by knocking an expensive loco off the table on to the floor or you can put up scenic barriers or not very tall fences. Minimum radius is what you can get your rolling stock comfortably around or what you like. Don’t ask for permission to experiment because there is always someone who says don’t. Have fun and all the best.

  • Randall Styxsays:

    The minimum radius on a model railroad is determined by two factors – one objective, the other subjective. First (the objective) is the minimum radius that can be negotiated by your motive and rolling stock. Too tight a turn and your stock will come off the track either because the wheel base can’t flex around the curve (6 or 8 wheel trucks or 3 or more drivers in a set on a steam loco) or because the weight of the train behind cars on the curve will pull those cars off. At times couplers will break loose if the curve is too tight, or the coupler arms will bump up against part of the car (like steps) and cause a derailment or breakage. If you’re modeling vintage railroads with 36 foot box cars and 4-4-0 locos, you can probably get by with even less than 9″ in N gauge. But if you want to run longer stock, you’ll need more. The Athearn “Big-Boy” will derail on anything less than 11″ and a minimum of 15″ is recommended by Athearn. Second (the subjective) is the minimum radius that looks good to your eye as your trains negotiate the curve. Marx, Lionel, and American Flyer got us used to radii much tighter than prototype tracks (and very few of us have the space accurately to model prototype curves). Few of us would like to see the entire width of the track visible at the middle of a car on the curve (like an 80 foot passenger or 89 foot auto carrier) even if the car goes around without derailing, and the angular broken line created by the train is unappealing for most. Articulated loco’s look strange with the fronts of their boilers suspended in mid air and their lead trucks pulled off to the side. But what is acceptable is a matter of personal preference. Many of us enjoyed O and S gauge tracks at 18″ radius (or Standard gauge at 21″ radius).

  • Stevesays:

    Hi. I’d like to ask the same question. I’m dreaming of building a OO9 mountain mining railway model with multiple levels, steep gradients, long tunnels, bridges and tight bends. Possibility even some gravity only tracks using microcontroller based optical speed sensors and pulsed electro-magnetic braking. I have lots of questions , but for now, Is minimum radii of 9″ and a gradient of 10-12% impractical ? I imaging a 0-4-0 loco pulling around 10 trucks or a handful of passenger cars. Thanks.

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