Thread: New 2018 Defender to share D5's Aluminium monocoque body.

Originally Posted by stealth

Does this sound like there will be a cab/chassis ute available? Doesn't to me.

A rear subframe would deal with that. I would think that to build a full monocoque utility style body would be near impossible anyway as there is not enough "meat" in the rear section to provide the strength required.

Sent from my Nexus 7 using AULRO mobile app

Originally Posted by stealth

But could you do that with aluminium? I coudn't imagine it would be strong enough.

Properly designed, an aluminium structure can be just as strong as a steel structure.

The critical property in any practical structure such as a car body is Young's Modulus (for practical materials). This is the factor that is relevant in Euler buckling, which is the failure mode of relatively long narrow structures in compression, such as the top of a chassis rail where the load is between front and rear wheels. Interestingly, for all practical materials (except some exotic ones- e.g carbon fibre), this property is proportional to the specific gravity of the material. This means that everything else being equal, steel and aluminium structures would be the same weight.

But everything else is not equal - a lot of the bits of the body have a minimum thickness requirement to cope with minor damage and corrosion - for the same strength, aluminium is about three times as thick, so a lot of it can be made the thickness needed for strength rather than this minimum thickness. And it is still likely to be stiffer than the steel part, simply because it is still perhaps twice as thick - and the dimensions come into the formula as well.

Consider, for example, the chassis of a Series Landrover. Except for a few reinforcing spots, it is all made of the same thickness metal, this being the minimum feasible thickness to sustain minor damage and corrosion - if it were made of aluminium, it would not have to be three times as thick - probably the top and bottom of the rails maybe twice as thick, sides the same thickness (an engineering calculation to decide), and a lot lighter - but significantly more expensive.

John