Anhängerbetrieb und Ladungssicherung - Trailer Operation and Load Securing
Trailer work is where category T combinations become unstable. The exam tests coupling, weight distribution and the physics of load securing.
Coupling and checks
- Correct drawbar height so the trailer rides level; the ball or ring coupling must latch and be secured with its pin.
- Breakaway cable or safety chain connected to a solid point on the tractor, not to the coupling itself.
- Two-line air brake: red to supply, yellow to brake line; test that the trailer brakes when you operate the tractor brake, and that the parking brake holds the trailer.
- Jockey wheel raised and locked, lights and indicators checked with a second person, mudguards and side markers present.
Weights and stability
- Stay within permissible trailer gross weight, axle load and the tractor's permissible towing capacity.
- Keep the nose weight (Stützlast) within limits - too little makes the combination pendulum, too much overloads the rear axle and lifts the front wheels, which costs steering grip.
- Load heavy items over the axles, low down; a high load raises the centre of gravity and starts roll-over in bends.
- Speed: 25 km/h for standard combinations, 40 km/h only where tractor, trailer and papers permit.
Load securing basics
The load must not shift, roll, slide or fall off. Use form fit first (front wall, side gates, stanchions), then friction (anti-slip mats), then force closure (lashing straps, chains). For road transport the load must withstand 0.8 g forwards, 0.5 g sideways and 0.5 g rearwards. Lashings need a legible label with lashing capacity (LC) and must be free of cuts and UV damage.
Worked example
A 1,000 kg seed pallet on a wooden trailer bed must be secured against 0.8 g forward, i.e. 800 daN. Bare wood on wood gives about 0.2 friction, so only about 200 daN is covered and 600 daN must come from the lashings. Two straps with LC 1,000 daN at a favourable angle, or bare wood replaced by an anti-slip mat with a much higher friction coefficient, close the gap. Reasoning: friction carries load only in proportion to its coefficient, so the residual force must always be calculated and covered by lashings.
Traps that cost marks
- Counting lashing capacity (LC) as if it were the full securing force, ignoring the angle.
- Securing only downwards, leaving the load free to slide forwards.