Aluminium Monocoque or Steel Space Frame Chassis?

Forgive me if this subject/question has already been covered before - I'm a newbie to this forum!!

I'm currently looking into a number of kits at the moment and I'm not sure whether to go with a Steel Triangular Space Frame or Aluminium Semi-Monocoque Chassis? The GT40 that I want to build will be primarily used for street applications (so it needs to be compliant to the current Australian Design Rules - ADRs) but with the view of having the occasional fun day at the track?

Whilst the aluminium semi-monocoque construction seems to have superior rigidity strength and stiffness, the material itself is prone to fatigue and cracking under various stresses (I used to be in the Ship Repair Industry in a former life) and to create a similar construction in steel would be too heavy. A material such as Magnesium Alloy (or similar) seems to be better for the application but the cost of materials and fabrication would be super expensive therefore doesn't even seem to be an option.

On the other hand - the Triangular Space Frame whilst constructed in steel (and is relatively light-weight) but may not be as rigid as the semi-monocoque design due to the fact that there would have to be triangular supports missing in the structure to allow for doors, room in the cabin, etc... thus adding to horizontal flexing at those points which reduces rigidity.

With my limited knowledge and understanding, I'm under the belief that the stiffer and more rigid the chassis/frame can be is directly related to the effectiveness of the suspension setup for handling performance (please correct me if I'm wrong).

I'd appreciate any thoughts on this subject.


Darren :laugh:
Darren welcome.

I have had long thoughts about making a tub in alloy sheet and solid rivets.
It would be much faster to put together than a space frame.

If it were me I would be reserching existing tubes that have gone the distance to get a grade.
I think part of the issue is race car tubs were never made to last,if they got a few seasons then that was good enough.
Maybe an air craft sheet metal worker would help with selection as an air frame would be under similar stresses I would think.

Sheet metal would be even easier if you use a spot welder gt40s are still going strong.
Let us know what you come up with.

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