## 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-sec^{2}-in

g = gravitational constant, in/sec^{2}

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-sec^{2}-in (p
62, bottom)

**Testing Equation 1: I**_{z} = 181043
lb-sec^{2}-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-sec^{2}-in

**Testing Equation 1: I**_{z} = 211190
lb-sec^{2}-in (approx 13% below published value)

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TRAILER MOMENT OF INERTIA