Tightest turn?

[shcsbaker]

I need to do a 180 degree turn on a table that is 15" wide.. this possible?  Part number of track if so?

Thanks,
Kevin

[ACY]

You need at least 32 inches to do a 180° turn in HO scale and that is using 15 inch radius which is the sharpest curved piece available in HO scale. A second possibility would be to install crossovers or turnouts to accomplish what you want but you will not be able to have continuous running and the train would have to travel in reverse on one track no matter what.

In N scale they used to make 9 & 1/2 inch radius, so you could turn 180° if you had 19 inches to work with.

With the space you have to work with you would need a Z scale set up to fit it on a 15" wide area.

In HO scale anything less than 15" radius is a bad idea and would require flex track of course, generally speaking 18" radius should even be avoided if possible. I try not to use anything less than 22" radius but there are a few applications such as for 2 axle trollies that I would use 15" radius or potentially make 12" radius with flex track.

It is not possible to operate an HO scale train on track smaller than 9" and that would be limited to a hand car or a very small 2 axle trolley. If you had any additional cars on the train they would derail, tip over or uncouple.
7 inch radius is what you would require for your space requirements but I have never heard of it ever being used successfully by even one person.

Hopefully you can free up at least 32" of space to allow you to use 15" radius which is available from Bachmann and other brands.

[Hunt]

The radius of curve track is measured using the center line of the track. So more than 30" space is necessity for half of a circle made using 15" radius curve track. Also, take into account the train overhang if need be.