Mechanized Infantry Perceptions 2010

[Compost]

To conserve weight and reduce corrosion the M-113A1 was built with aluminium alloy armour that has a density of about 2750 kg/cu-m. The thickness of that armour was approx 40mm which provided almost the same degree of ballistic protection as would 13 mm of steel. However the increased thickness and stiffness of the aluminium plate meant that it was largely self-supporting and hence the hull needed few structural beams and ribs. The overall result was much lower vehicle weight than an M-113 built with steel armour.

During the 1960s aluminium armour became less popular because it tends to tear when subject to mine blast and also melts at a lower temperature than steel. Upgraded versions of the M-113 carry a steel belly plate and many have an outer skin of flat or corrugated aluminium or steel. Vehicle weight of the M-113A2 increased from 12 to about 15 tonnes in the M-113A3. The extended M-113A4/MTVL (Mobile Tactical Vehicle Light) with an extra wheel station and more powerful engine has a maximum all-up weight of about 18 tonnes.

Despite the formalisation of ballistic, shrapnel and mine blast threats there are still no commonly agreed meanings or boundaries for light (weight) as opposed to medium (weight) or heavy (weight) armoured vehicles. In some contexts the term light is used to mean vehicles weighing up to about 7 tonnes but in others the term is applied to vehicles such as the M-113 that weigh twice as much and more. So vehicle weight or mass is often discussed using relative terms without boundaries or a clearly understood specification.

The use of weight descriptors with agreed meanings is important because the all-up-weight of an armoured vehicle is a major factor in determining its primary attributes of armament, mobility and protection. Also weight highlights – again indirectly – some of the capabilities and vulnerabilities of armoured vehicles and units. Additionally it makes it easier to assess an armoured vehicle in one weight category against a generally similar vehicle in another category.

Various categorisations of weight can be devised using arbitrary or incremental limits but each is artificial and can become complex as in Table 1. And any such rigorous system of categories is likely to be acceptable only to pedants or Queensbury-style enthusiasts.