v005b, with the added sway bar linkage.
Suspension link trusses
Solid circular beam sections, ø12mm, aluminum. Essentially rigid with respect to other chassis structures.
Hollow circular section beam, aluminum.
Main structure: outer diameter ø40mm, wall thickness 1.8mm.
Stiffeners: outer diameter ø30mm, wall thickness 1.2mm.
Thicker backbone: 1.8mm aluminum sheet, 25.4mm aluminum honeycomb 3003, density 5.2 lb/ft^3 (hex-3003-td.pdf), 1.8mm aluminum sheet.
Thinner panels: 1.8mm aluminum sheet, 6.75mm same aluminum honeycomb, 1.8mm aluminum sheet.
Frontal shock absorber support plate: provisionally as thinner panels, to be defined based on shock.
Sway (anti-roll) bar
outer diameter ø25mm, wall thickness 2mm, extremely stiff (Super-alloy Z,
nu=0.3); it may be mechanically isolated at need by deactivating one of the connecting elements to the wheel hub carriers.
Such a “deformable but extremely stiff” linkage modeling should be discouraged in favor of an actual kinematic constraining – i.e. an MPC, since excessive stiffness badly impacts the system matrix condition number (or the integration time step, in the case of explicit dynamic simulations); nonetheless, it allowed for a very straightforward implementation.
The pedagogical model proposed does not include sway/antiroll bars, that are instead a critical element for torsional stiffness loadcases.
In particular, torsional stiffness should be evaluated in both the limiting cases of
This second loadcase, which is usually neglected, is however relevant for sizing the sway bar support areas on the chassis structure.
On the relevance of constraining in dynamic analyses. back view side view relevance of (improper) constraints on the dynamic behaviour of a structure. Design is reliable in actual operational conditions (link). Added constraints stiffen up the structure, thus increasing natural frequencies. However, a 0 Hz rigid body mode natural frequency may rise to a finite value due to added positioning constraints; the associate natural mode may be excited in resonance by dynamic loads.
How to set a damped response
Poor man dynamic response animated view
Structural damping references
estratto vol. 2, sezione 8 di Soovere, J., and M. L. Drake. Aerospace Structures Technology Damping Design Guide.LOCKHEED-CALIFORNIA CO BURBANK, 1985.
crash_absorber_bearing_areaset (an approx. 155×320 mm area at the front bulkhead), a 25 psi = 0,172 MPa distributed pressure is applied which is due to the honeycomb absorber crushing (see datasheet).