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

          W_F= Weight Front, lbs.

          W_R = 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”, W_f=8960, W_r=6540, A=60.8, B=83.2

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

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

 

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

WB = 142”, W_f=9437, W_r=7953, A=65, B=77

I_z = 241479 lb-sec²-in

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

 

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TRAILER MOMENT OF INERTIA