Construction and Processing materials over time

To get an understanding of the materials used in a motor vehicle, we look at parts and what they would have been made of.

Engine block

The desired materials for engine blocks should be:

  • Able to be cast
  • Able to be machined
  • Resistant to high temperatures
  • Resistant to impact loads
  • Thermally conductive
  • Able to retain its shape under many different circumstances
  • Able to dampen the vibrations from the pistons
  • Lightweight

Some of the materials used:

  1. Grey cast iron
    • Great vibration dampening
    • Heavy
    • Usually cast in one piece, then machined if this is the case. Called a monoblock if done so.
  2. Aluminium alloys
    • Lightweight
    • Alloys create a variety of possible mechanical properties
      • Some of the alloys used can be from Nickel, Chromium or Magnesium
    • Usually Pressure or Gravity casted.
    • Occasionally requires the use of cast iron inserts to withstand the loads.

Pistons

The desired materials for pistons should be:

  • Able to be machined
  • Resistant to impact loads
  • Resistant to high temperatures
  • Thermally conductive
  • Able to retain its shape under varying circumstances
  • Lightweight

Some of the materials used:

  1. Aluminium
    • Lightweight and easily machinable
    • Spray coatings may be applied to reduce wear on the cylinder walls

Crankshafts

NB: Crankshafts are those things that spin to move the pistons up and down.
The desired materials for crankshafts should have:

  • High tensile strength
  • High fatigue strength
  • Shape stability
  • Machinability

Some of the materials used:

  1. Cast iron
    • Easy to cast into its intricate shape
    • Good wear resistance
    • Could be replaced with ductile Carbon steels
    • Was used a while ago
  2. Alloyed steel
    • Usually forged and then heat treated to appropriate qualities
    • A common alloy is Vanadium
    • Lightweight
    • Better shape stability
    • Impact dampening

Body Panels

The desired materials for body panels should have:

  • Good strength to weight ratio
  • Good surface finish
  • Formability
  • Toughness/Scratch resistance
  • Corrosion resistance
  • Weldability and Ease of manufacture
  • Recyclability

Some materials used were

  • Aluminium (Pre-1916)
  • Steel and steel alloys
    • High formability
    • Alloys reduced weight while maintaining tensile strength.
    • Stainless steels also reduce corrosion resistance.
  • Alternatives such as Aluminium alloys and thermoplastics allow for recyclability and corrosion resistance.

Frame

Good frames should have

  • Lightweight
  • Stiffness
  • Fatigue strength
  • Weldability
  • Corrosion resistance

Some materials used were

  • Steel alloys
  • Aluminium Alloys
    • Joined with rivets as it is harder to weld
    • Corrosion resistant

Windscreens

  • Laminated glass was introduced in 1927.
  • Tempered glass was introduced in the 1950s.
    • It is used for rear windows as it obstructs vision.

Wheels

  • In 1920s a solid disc riveted to the rim was introduced over the previous "axle goes immediately to tyre"
  • This was better as they resisted the wheel flexing while turning.
  • Today cast aluminium, fabricated steel or magnesium alloys are used
    • Mostly cast aluminium alloys due to their formability, fatigue strength and impact resistance.

Tyres

  • Originally, tyres had no tread pattern
  • It was introduced in 1916, and vastly improved road-holding abilitiies

Good tyres have high

  • Friction/Traction
  • Wear resistance
  • Shock absorption/Vibration dampening
  • Abillity to not fail under petrochemical attacks.

Materials used include

  • Rubber
    • Universal material for tires
    • New construction methods in 1948 (radial ply) helped improve passenger comfort and reduced wear.

QUICK SUMMARY

  • All uses of timber have been replaced by iron, steel, and aluminium over time.
  • Iron has been largely replaced by steel except in engine blocks which are still commonly cast iron.
  • Aluminium and aluminium alloys have started to replace steel in areas where weight is an issue due to its better strength-to-weight ratio.
  • Alloy steels with manganese etc have been developed for specialised uses over plain carbon steels.
  • Stainless steel is now popular for cables and pins due to its high corrosion resistance.
  • Carbon fibre is an excellent alternative to aluminium or alloy steel frames due to its high strength-to-weight ratio.
    • However when it fails it is sudden and catastrophic.
  • Rubber has been replaced with synthetic rubber.
  • Polymers have found use where insulation is needed, or when high strength is not important
    • eg cable coverings, dashboards, handles etc