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What's a suitable radius to use with HO scale auto racks and other long cars? I mean more than just a operational minimum radius, what actually will look good? They will be viewed from only the inside of the curve, I don't know if that will make any difference or not, but I would think too sharp a curve with a long car would look far dumber from the outside of the curve than the inside because the track would be sticking out at the middle of the car.


Been Nothin' Since Frisco
If you can go 36" or more, I think you'll be pleased. Viewing the curve from the inside will help dramatically in comparison to the detraction it would offer if viewed from the outside, but the broader you can make the curve, the better.

Think about this: a 10 Degree curve (572.96' radius) on the prototype is considered "sharp" for a mainline curve. That's the type of curve you'd find near Tehachapi Pass or some place like that. The typical trainset comes with 18" radius track, which is equivalent to a 45 Degree curve (130.65' radius). Here are the radii and Degrees of curve for whole feet from 2 to 7 foot radius curves:

24" radius = 33 Degree curve (174.20' radius)
36" radius = 22 Degree curve (261.30' radius)
48" radius = 16½ Degree curve (348.40' radius)
60" radius = 13 Degree curve (435.50' radius)
72" radius = 11 Degree curve (522.60' radius)
84" radius = 9½ Degree curve (609.70' radius)

Now, for industrial trackage you can get away with more. There's an industrial complex near my place of business that's adjacent to a GM plant. The tracks that curve away from the main line go between warehouses and make some pretty tight curves, the tightest of which are 300' radius. That's still a 41" radius curve in HO!
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Excellent food for thought, thanks. :) I'm not sure if I can squeeze 36" radii in all 4 corners, but I think I'll definitely be over 30" in all of them on the inner loop.

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