semi-trailer truck

Semi-trailer truck – a large vehicle that consists of a towing engine, known as a tractor or truck, attached to one or more semi-trailers to carry freight. A semi-trailer is attached at a point that is just forward of the rear-most axle of the towing unit. This is done so that a large portion of the weight of the trailer is carried by the prime mover.
What’s the problem?
To move the maximum amount of cargo, the trailer cargo space of the truck can be loaded and unloaded while the tractor unit is being used to haul other trailers.

• Ask – For many trucks, the truck is a single unit with the engine, the driver’s cab and the cargo space all together on a frame with wheels front and back. How can the trailer and tractor units be separated? What would have to be connected for use on the road?
• Imagine – What are some other examples of cargo spaces? Can these be adapted for transporting cargo by road?
• Plan, Create – How can the cargo trailer be adapted to be parked independently from the tractor unit? How are safety systems such as brakes and lights on the trailer controlled from the trailer for road use?
• Improve – Some cargo is transported by ship, train and road from one place to its destination. How can a cargo space be designed so that it can be transported by all these means?

That’s engineering

1. tractor unit
2. semi-trailer
3. engine
4. cabin
5. sleeper (not seen in all trucks)
6. wing
7. fuel tank
8. fifth wheel coupling
9. cargo space
10. landing gear – legs for when semi-trailer is taken off
11. tandem axles