Torque Steer

Example Calculation

Step 1: Calculate Polar Moment of Inertia

Shaft OD: 0.8"

Shaft ID: 0.5"

Shaft Area of Inertia: pi/32*(D^4-d^4) = 0.034076in2

Step 2: Calculate Torsional Stiffness

Shaft Material: 4130 Steel

4130 Shear Modulus: 80 Gpa or 1.16e+7 psi

Left Shaft Length: 15 in

Right Shaft Length: 19 in

k = G*J / L

Left Torsional Stiffness (k_L): 38.3379023 lb-ft / degree

Right Torsional Stiffness (k_R): 30.26401 lb-ft / degree

Step3: Find Torque

Max Torque from Engine (Launch): 40 lb-ft

Final Drive Ratio: 3.55

Torque Seen by Driveshaft: 142 lb-ft

Step 4: Find Shaft Twist

phi = T / k

Left Shaft Twist (phi_L): 3.704 degrees

Right Shaft Twist (phi_R): 4.692 degrees

Step 5: Find Vehicle Yaw

Tire travel (T) = Shaft twist/360 * Tire Circumference

Yaw = arcsin(T_max-T_min / Track Width)

Circumference of Tire: 56.52 in

Left Tire Travel: 0.582 in

Right Tire Travel: 0.737 in

Rear Track: 36 in

Yaw: 0.247 degrees