TRACTOR MOMENT OF INERTIA

Formula from Phase 4 report (Reference 19, Appendix F, p 293 for Tractor Yaw Moments of Inertia:

Using the recommended value of a=0.4 from Reference 19 and symbols from m-smac the equation Tractor Yaw Moments of Inertia is as follows:

Equation 1

Where: Iz = Yaw Moment of Inertia, lb-sec2-in

g = gravitational constant, in/sec2

WF= Weight Front, lbs.

WR = Weight Rear, lbs.

A, B = CG to front/rear axles of Tractor, inches

Testing the equation by comparison with published values:

From reference 21: (Baseline Vehicle, p 56-82):

WB = 144, Wf=8960, Wr=6540, A=60.8, B=83.2

Iz = 214216 lb-sec2-in (p 62, bottom)

Testing Equation 1: Iz = 181043 lb-sec2-in (approx. 16% below published value)

From reference 22: (1977 GMC Astro COE Tandem Tractor, p 126):

WB = 142, Wf=9437, Wr=7953, A=65, B=77

Iz = 241479 lb-sec2-in

Testing Equation 1: Iz = 211190 lb-sec2-in (approx 13% below published value)


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TRAILER MOMENT OF INERTIA