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출처: CDL Manual — Doubles and Triples (§7)마지막 확인: 알 수 없음 · 아직 확인되지 않음
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Pulling Doubles and Triples
Why doubles and triples need special care: they are less stable and more likely to roll over because of the crack-the-whip effect (the last trailer whips hardest), so steer gently and slow down for curves; allow more following distance and space; and converter dollies built on/after March 1, 1998 must have antilock brakes (a yellow lamp on the left).
Coupling and Uncoupling
Coupling and uncoupling doubles/triples correctly — basic to safe operation, and dangerous if done wrong: securing the second trailer, handling the converter dolly, the coupling and uncoupling sequences, coupling triples, and the key caution — never unlock the pintle hook while the dolly is still under the rear trailer (the tow bar may fly up).
Inspecting Doubles and Triples
The extra inspection items on doubles/triples (beyond the Section 2 seven-step inspection): the fifth wheels (lower and upper), air and electric lines, the sliding fifth wheel, landing gear, and the shut-off valve positions — the valves at the rear of the front trailers must be OPEN and at the rear of the last trailer must be CLOSED, with the converter dolly air tank drain valve CLOSED.
Checking Doubles and Triples Air Brakes
The extra air-brake checks for doubles/triples: the air-flow test (open the emergency line valve at the rear of the last trailer — you should hear air, proving the whole system is charged), testing the tractor protection valve (it should go to emergency, usually 20-45 psi), and testing the trailer emergency and service brakes.