Narrow-Track Wheeled Agricultural Tractor Parameter Variation

Despite a general consensus among farmers, manufacturers, and researchers that wheeled agricultural tractor design has changed over time, there is little published evidence. There is debate as to whether the standardized rollover protective structure (ROPS) energy and force requirements, based on a tractor reference mass and pertaining to studies conducted more than 40 years ago, are appropriate for modern tractors. This article investigated the physical parameters of 326 modern narrow-track tractors, meas- ured according to OECD Code 6 over 16 years (1993 to 2008 inclusive): 252 (~77%) were fixed-chassis tractors and 74 (~23%) were articulated. To understand the signifi- cance of design changes, the data were analyzed with respect to time and as a function of tractor mass. Articulated and fixed-chassis data were treated separately. The time data allowed qualitative analysis, while the mass data allowed quantitative analysis. The pa- rameters show some changes over time and clearly indicate differences between articu- lated and fixed-chassis types. The parameter changes, along with the differences between types, may have important safety ramifications for ROPS energy absorption require- ments, and these aspects are discussed. Regression lines with R2 values were fitted to the mass-related data for fixed-chassis and articulated tractors to determine the suitability of fit. The mass relations also displayed differences between fixed-chassis and articulated tractors. Thus, the most significant recommendation from this study is that the standard- ized testing procedure for narrow-track wheeled agricultural tractor category should be split into two groups: fixed-chassis and articulated.