In the Brixius traction prediction equations for pneumatic tires on agricultural soils, which of the following variables are included in the dimensionless tire Wheel Numeric (Mobility Number $N$)?
Options:
(A) Soil Cone Index ($CI$)
(B) Unloaded tire overall diameter ($d$) and section width ($b$)
(C) Dynamic vertical load on the wheel ($W$)
(D) Tire inflation pressure exclusively without considering tire deflection ratio
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
- **Brixius Mobility Number ($M$ or $N$):**
$M = \frac{CI \cdot b \cdot d}{W} \left(\frac{1 + 5 \delta/h}{1 + 3 b/d}\right)$
where:
- $CI$ is the soil cone index (strength)
- $b$ is section width
- $d$ is tire outer diameter
- $W$ is dynamic vertical wheel load
- $\delta/h$ is tire deflection ratio (fraction of section height)
- Statement D is incorrect because deflection ratio $\delta/h$ is explicitly used rather than bare inflation pressure.