Close coupling (close coupler)

A close coupler keeps adjacent cars tight together on straight track but lets the gap open automatically in curves. This is done by a close-coupling mechanism — a small cam pocket (standardised via the NEM 362 socket) in which the coupler slides back as the car enters a curve. It looks prototypical but is sensitive to tight radii and S-curves: there the car ends swing out sharply, the mechanism can bind, and when propelling — for instance downhill — it pushes the leading car off the track. Long, close-coupled vehicles therefore need more generous radii and straight sections between reverse curves than rigidly coupled ones.