help with planning curves

[TankerR3D]

working on the earlyu stages of building an N scale modern layout, what is the minimum curve i could get by with, while still looking halfway prototypical for newer equipment, like stack trains, unit coal, and big six axle power.....also longer cars like auto racks

[CTValleyRR]

Our hosts at Model Railroader define curves in N scale as follows (freely plagarized):

Broad: 17"

Conventional: 14"

Sharp: 11"

According to MR, broad curves will handle just about anything, conventional will take up to a 4-6-2, 2-8-2, or 6 axle diesel, and freight and passenger cars 80 scale feet or shorter.  Sharp curves should be limited to 4 axle diesels, small steamers, and cars under 60 scale feet.

Adding easements (a gradual transition into your curves) will make longer equipment perform better, but you still won't get an 85' heavyweight coach to look good or work well on an 11" curve.

There is also an NMRA Recommended practice, located here.

Good luck!