| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 799911 | Journal of Terramechanics | 2014 | 7 Pages |
•Soft soil traction/slip properties are required for vehicle performance models.•The Magic Formula can be adapted to represent soft soil traction/slip properties.•The Magic Formula is used for describing the force/slip of tyres on road surface.•The Magic Formula is used in conjunction with Mobility Numbers.•Mobility Numbers are used to describe traction coefficients of tyres in soft soil.
The tractive force/slip relationships of pneumatic tyres are required as inputs to vehicle performance prediction models such as the NATO Reference Mobility Model. They can also be used to calculate the tractive efficiency and work output of vehicles such as farm tractors, especially important when the vehicles are performing high drawbar pull operations; the effects of altering tyre size, tyre pressure and ballast can be predicted. The so-called Magic Formula is widely used for describing the force/slip relationships of pneumatic tyres on hard road surfaces. The coefficients in the Magic Formula are derived from experimental measurements. Relationships are then developed to describe the coefficients as functions of normal load on the tyre. The paper describes how the Magic Formula can be adapted to describe the tractive force/slip relationships of tyres in soft cohesive soils. The coefficients are made functions of Mobility Number instead of normal load. Mobility Number is an empirical system for estimating the tractive performance of tyres in soft soils at a single value of slip. The method could be extended to cover lateral tyre forces or other soil types if suitable experimental data is available.
