As everyone on this forum knows, the engine of every F1 car doubles as the rear part of the chassis, and has done so since the Lotus 49 and the Ford DFV engine of 1967. Or, pedantically speaking, since the Ferrari Flat-12 of 1965 and the BRM H16 of 1966.
What is perhaps less well known is to what extent the engine contributed to increased torsional stiffness of the assembly: I for one have not been able to find anything on this subject. Of course, the figures for the cars of that era have surely been improved upon, by at least an order of magnitude, with the developments since then: the substitution of bonded aluminium sandwich for plain riveted aluminium sheet probably the first major step forward, this material in turn superseded by the moulded carbon-fibre-reinforced plastics that have long since become universal. The contribution of the engine is a lot harder to evaluate, not much relevant information ever having been made public, as it appears.
Torsional stiffness is actually only one aspect of chassis performance, bending stiffness in both longitudinal planes being probably of no less significance. Aerodynamic loads have certainly seen to that, their fore-and-aft distribution just as important as their considerable magnitude. Together with the weight distribution, the aerodynamic forces directly influence the bending moments in the vertical plane, and indirectly, through the cornering loads at each tyre contact patch, those in the horizontal plane. In fact, as the aerodynamic loads are symmetrical across the width of the car, it seems logical that they don’t contribute at all to torsional loading, so that the magnitude of these should not be radically different to those of 50 years ago.
Has anyone seen any figures and/or informed discussion of these matters in any published work? I imagine that it would have to be authored by someone with a background in racing car design and construction (as opposed to the enthusiastic amateurs we are all familiar with): Peter Wright, Gordon Murray and Adrian Newey come to mind, among a host of other true professionals in the field.