Degree Type


Date of Award


Degree Name

Master of Science


Agricultural and Biosystems Engineering


Agricultural and Biosystems Engineering

First Advisor

Stuart Birrell


The agricultural world is developing tires with new capabilities that improve heavy machinery’s fuel efficiency, tractive force, and ride comfort. To minimize cost, a manufacturer could use the Brixius or Wismer-Luth soil - traction dynamic model to predict how a vehicle’s tire would perform out in the field without performing expensive field tests. However, these models have two major drawbacks, inconsistent soil cone index readings and inaccurate tire dimension representations. Since empirical analysis was used to generate a tire’s tractive capability characteristics, only the tire evaluated and the field conditions present during testing are represented well by the model. This increases error when comparing different tires in different conditions.

To provide a model that provides a reliable evaluation of tractive performance, an agricultural tire dynamometer was proposed. The proposed dynamometer eliminated the cone index altogether so that engineers could see what relationship a wheel’s dimensions have on its tractive performance independent of cone index readings. To eliminate the cone index, the test stand will utilize a set of belts to study the interaction between the tire and a well-defined surface. The test stand is able to control the torque, down pressure, contact area, and velocity of the agricultural tire in question, while providing accurate and reliable data to analyze.

This thesis contains a literature review of the soil traction dynamic models. Then, a detailed description of how the parts were sized and selected for the dynamometer. Finally, the characteristics and outputs of the test stand were modeled. The system was simulated to investigate its performance.

The dynamometers capabilities were discussed along with future work that could provide improvements. Future work could include the system control of the contact area between the tire and belts. Also, a method of quickly changing the belts if needed.

Copyright Owner

Colton Finley



File Format


File Size

86 pages