Ohio CDL Combination flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fifth wheel jaws
- The locking mechanism that grips the trailer kingpin. After backing under, pull forward against the locked trailer brakes to verify the jaws are closed and the coupling is secure.
- Kingpin
- The vertical pin mounted under the trailer nose that the fifth wheel jaws lock around. Inspect it for bends, cracks, and wear before coupling.
- Tug test
- With trailer brakes locked, shift into a low gear and gently pull forward. If the trailer holds the tractor back and does not move, the coupling is likely secure.
- Trailer supply line
- The emergency air line that charges the trailer tanks and signals a breakaway. If it separates, the tractor protection valve closes and the trailer spring brakes set.
- Service air line
- The line that carries the driver's brake-application pressure to the trailer relay valve. A kink or leak here causes weak or delayed trailer braking.
- Tractor protection valve
- A valve that shuts off air to the trailer when pressure falls too low or a line separates, protecting the tractor's air supply and applying trailer emergency brakes.
- Trailer spring brakes
- Fail-safe brakes held off by air pressure. When air is lost or the emergency line separates, springs apply the brakes automatically, so the trailer cannot roll away.
- Landing gear
- The retractable legs supporting a dropped trailer. Lower them to firm ground, crank until they bear weight, and raise them fully before towing.
- Fifth wheel plate
- The greased horseshoe plate on the tractor that supports the trailer. Check for cracks, secure mounting, and adequate lubrication before coupling.
- Off-tracking
- The tendency of a trailer's rear wheels to follow a path inside the tractor's front wheels during a turn. Sharper turns and longer wheelbases increase it.
- Swing wide
- A turning technique that moves the tractor farther from the curb so the trailer's rear wheels clear the corner without striking objects or the curb.
- Rearward amplification
- The tendency of the rear trailer in a multi-trailer combination to swing wider than the tractor in sudden maneuvers, increasing rollover risk.
- Snap rollover
- A rollover caused by rapid steering that sets off rearward amplification in doubles or triples. Prevent it by steering smoothly and slowing before maneuvers.
- Converter dolly
- A small axle-and-fifth-wheel unit that attaches a second trailer to a tractor-trailer set. Its air lines and locking jaws must be checked before driving.
- Glad hands
- The couplers joining tractor and trailer air lines. Seal them with rubber gaskets, lock both halves, and check for leaks after coupling.
- Electrical cord
- The cable carrying lights and signals to the trailer. Plug it in after the air lines, route it to avoid chafing, and confirm trailer lights work.
- Air leakage check
- With the engine off and brakes released, watch the gauge: a combination should lose no more than 3 psi in one minute.
- Trailer hand valve
- The red trailer-brake control on the dash. Use it to test trailer brakes independently and to check that the service line is connected correctly.
- Breakaway protection
- A system that sets the trailer spring brakes if the trailer separates from the tractor, powered by the trailer's own air tank through the emergency line.
- Bobtail braking
- Driving the tractor without a trailer. It stops faster and can lock the rear wheels easily, especially on slick pavement, so brake gently.
- Total stopping distance
- Perception distance plus reaction distance plus brake lag plus effective braking distance. Air-brake lag and heavy loads lengthen it substantially.
- Brake lag
- The delay between pressing the pedal and air reaching the trailer brakes, roughly a fraction of a second. It adds distance at highway speed.
- Space cushion
- The gap around your combination. One second per ten feet of vehicle length plus one second is the minimum following rule for heavy rigs.
- GOAL
- Get Out And Look. Before backing a combination, walk around the rig to check clearance, obstacles, and trailer alignment when mirrors are not enough.
- Backing a trailer
- Hold the bottom of the wheel and turn toward the direction you want the trailer to travel. Small corrections early prevent jackknifing.
- Jackknife
- A loss of control where the tractor and trailer fold sharply at the coupling. Caused by locked trailer wheels or braking hard on slick surfaces.
- Trailer brakes first
- A control rule for slick roads: the trailer hand valve lets you apply trailer brakes slightly before tractor brakes to keep the rig stretched out.
- Coupling air line order
- Connect the emergency (supply) line first, then the service line, then the electrical cord. Shutoff valves must be open and gaskets intact.
- Uncoupling steps
- Chock wheels, lower landing gear, disconnect lines and cord, release the fifth-wheel lever, then pull forward slowly and check the trailer is stable.
- Trailer height check
- Confirm the trailer's published height and compare it with posted clearances before driving. Low bridges and overpasses cause the most serious combination accidents.
- Tire and load check
- Inspect tires for pressure, tread, and damage, and confirm the load is secured. Underinflation and shifting loads are common causes of combination crashes.
- Slow down for curves
- A combination's high center of gravity makes it prone to rollover. Reduce speed before entering a curve and accelerate gently after the trailer follows through.