Minimum Radius: Will This Car Take My Curve?
Longer cars need broader curves, and a coupler can only swing so far before it binds or pulls apart. Pick the car you run and your curve radius for a straight CLEARS or TOO TIGHT answer, with a top-down view of two cars meeting on the curve.
How far the coupler can swing.
Will it take the curve?
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Tightest curve this car takes
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Coupler swing at your radius
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Car bodies
Couplers at the joint
Track centerline / rails
The governing minimum is whichever is more restrictive: coupler-limited (= coupler overhang / sin(swing allowance)) or a length-based guideline (longer cars want broader curves). Per-car coupler offset on a curve = asin(overhang / R). Confirm a tight fit by rolling your longest car through. Next, see how far the car swings past the railhead in the Overhang & Clearance tool.