McHenry Forum - Crash Reconstruction & Simulation

Q: I've been using I = m*0.92/12*(L^2 + W^2) for my Yaw Moment of Inertia calcs. Is this formula something that is generally used?

A: Not sure where the factor 0.92 comes from as that look very similar to the rectangular block of uniform density approximation technique from Grime & Jones,

• Car Collisions - The Movement of Cars and Their Occupants in Accidents", IME, Vol 184, Part 2A, Number 5).

You'll see that and other formulas in:

• Yaw Inertia
  a section from our currently our of print book McHenry Accident Reconstruction.
  The section presents some techniques (including the above referenced Grime/Jones formula) and references some additional papers with approximation techniques.
  For msmac licensee, the same information can be found in our msmac Help file
  • medit3D->Help menu->msmac Input Manual
    • see section DISCUSSION: Moment of Inertia