Dynamic response of small agricultural drive tires

Stiffness and damping properties were measured for 9.5-20 bias and radial agricultural drive tires at three inflation pressures. Vertical properties were determined with load-deflection, non-rolling and rolling free vibration tests. Torsional properties were determined with torque-deflection and torsional free vibration tests.; Higher vertical stiffness values were achieved from non-rolling free vibration than load-deflection and rolling free vibration. The non-rolling vertical stiffness for the bias tire was about 50 percent higher than that obtained from load-deflection. Higher vertical stiffness values were achieved from load-deflection than rolling free vibration.; With load-deflection and non-rolling free vibration, the bias tire was approximately 40 percent stiffer than the radial while rolling free vibration showed the bias tire was 25 percent stiffer than the radial. Vertical damping coefficients from non-rolling free vibration were 50-70 percent higher than those from rolling free vibration.; The torsional stiffness for the bias tire was about 50 percent greater than that of the radial tire for both measurement methods.; Torsional damping increased with increasing deflection and decreasing inflation pressure. The torsional damping coefficient for both tires increased 15 to 20 percent over the range of torsional deflections.; Tire behavior due to the slip-stick phenomenon was simulated using a two degree of freedom model that allowed torsional movement of the tire carcass relative to the wheel and vertical movement of the tire on a swing arm. Tire response was simulated for each tire at three inflation pressures. The method of measuring tire properties had an impact on simulation results, but not much impact on carcass movement due to the slip-stick phenomenon. Differing stiffness values resulted in different equilibrium positions for the various simulations. Increased damping resulted in a higher rate of decay of oscillations. Inflation pressure had more impact on tire stability than tire property measurement methods. Even though both tires were modeled at rated load for each inflation pressure, the reduced torsional damping at higher inflation pressures resulted in a less stable system. The bias tire was more stable than the radial.