Subtopic: Calculation of power, torque, fuel consumption, heat load and power losses
Question Statement:
For the tractor in the previous problem with wheelbase $2.1\text{ m}$, static front axle weight $8.0\text{ kN}$, and hitch height $0.45\text{ m}$, calculate the critical horizontal drawbar pull in $\text{kN}$ that will cause impending front-wheel liftoff (rearward overturning).
Answer Key:
37.33
Step-by-Step Solution & Explanation
Front-wheel liftoff occurs when the dynamic load on the front axle drops to zero ($R_{df} = 0$).
$R_{df} = R_{sf} - \frac{P \times h_d}{L} = 0$
$P_{\text{crit}} = \frac{R_{sf} \times L}{h_d} = \frac{8.0\text{ kN} \times 2.1\text{ m}}{0.45\text{ m}} = \frac{16.8}{0.45} \approx 37.33\text{ kN}$
Acceptable range: $36.5 - 38.0\text{ kN}$.