What cars are made of
Designers pick a material for each part by asking: how strong, how heavy, how costly, how safe, and can it be shaped?
- Steel: strong and cheap. Body, frame, axles, springs.
- Aluminium: about one third the weight of steel. Engine blocks, wheels, some body panels.
- Plastics: light and easy to mould. Bumpers, dashboard, fuel tank.
- Rubber: grips and soaks up shock. Tyres, hoses, seals.
- Glass: clear. Safety glass for windows (the windscreen holds together when it cracks).
- Copper carries electricity in wires.
Processing: shaping and joining
Raw material becomes a part by these steps:
- Cutting: shears, saws, laser or plasma cutters.
- Bending and pressing: a press forces a sheet into a mould to make a door or bonnet.
- Casting: melted metal is poured into a mould, as for an engine block.
- Forging: hot metal is hammered into shape, as for a crankshaft. It becomes very strong.
- Machining: lathes and drills cut metal to exact size.
- Moulding: hot plastic is pushed into a mould.
- Joining: welding, riveting, bolting and gluing.
- Heat treatment and coating: heating makes parts harder; paint, zinc coating and oil stop rust.
Tools and methods in car maintenance
Tools are used for a job, in a safe way:
- Hand tools: spanners, sockets, screwdrivers, pliers, hammers.
- Torque wrench: tightens a bolt to an exact torque (turning force, N·m). Too loose can fall off; too tight can snap the bolt.
- Measuring tools: ruler, vernier caliper, micrometer, feeler gauge, tyre gauge.
- Lifting tools: jack, jack stand, vehicle lift. Never work under a car held only by a jack.
- Power tools: drill, grinder, impact wrench.
- Testers: multimeter, compression gauge, scan tool.
Safety: eye protection, gloves, wheel chocks, clean floor, and the right tool for each bolt (a wrong spanner rounds the head).
Recycling automotive materials
A car at the end of its life is called an end-of-life vehicle. Recycling steps:
- Drain fuel, oil, coolant, brake fluid and refrigerant. Remove the battery. Store them safely.
- Remove parts that can be reused or rebuilt (engine, tyres, glass, seats).
- Crush and shred the body. Magnets pull out steel; other machines sort aluminium, copper and plastics.
- Melt and remake steel and aluminium. Aluminium recycling uses only about one tenth of the energy of new aluminium.
Batteries go back to makers (lead is recycled many times). Tyres become crumb for roads and floors. Good design makes parts easy to take apart and mark the plastic type.
Try it: torque and sort
Use the torque slider in the 3D. Find the green range. Then list five things in your home and write whether each is steel, aluminium, plastic, rubber or glass, and how it could be recycled.
Key formulas and definitions
- Torque (N·m) = force (N) × spanner length (m)
- Mass = density × volume
- Recycling rate (%) = recycled mass ÷ total mass × 100
- Key terms: alloy, casting, forging, machining, torque, end-of-life vehicle
Worked examples
1. You push a spanner with 50 N at 0.2 m from the bolt. What is the torque?
Torque = 50 × 0.2 = 10 N·m.
2. A bolt needs 60 N·m. The spanner is 0.4 m long. What force do you push with?
Force = 60 ÷ 0.4 = 150 N.
3. A car weighs 1,000 kg. 750 kg is recycled. What is the recycling rate?
750 ÷ 1,000 × 100 = 75%.
4. A steel door is 12 kg. The same door in aluminium is one third the mass. How much is saved?
Aluminium door = 12 ÷ 3 = 4 kg. Saved = 12 − 4 = 8 kg.
5. Pick the process: (a) engine block from molten metal, (b) crankshaft hammered hot.
(a) casting. (b) forging.
Common mistakes
- Using a longer tube on a spanner to over-tighten. This snaps bolts; use a torque wrench.
- Working under a car held only by a jack. Always use jack stands.
- Mixing recyclable materials in one bin so they cannot be separated.
- Pouring drained oil and coolant on the ground; they must be stored for recycling.