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A study was conducted to determine the accuracy of Wismer-Luth and Brixius equations in predicting net traction ratio of a high-lug agricultural tyre. The tyre was tested on a sandy clay loam soil in an indoor University Putra Malaysia (UPM) tyre traction testing facility. The experiment was conducted by running the tyre in driving mode. A total of 126 test runs were conducted in a combination consisting of three selected inflation pressures (i.e., 166, 193 and 221 kPa) and two wheel numerics (i.e., 19 and 29) representing two extreme types of soil strength under different levels of travel reduction ranging between 0% and 40%. Regression analysis was conducted to determine the prediction equation describing the tyre torque ratio. Marqurdt's method used by Wismer-Luth for predicting non-linear equation was not found suitable in predicting the torque ratio of the test tyre awing its low coefficient of determination and inadequacy. The logarithmic model was found suitable in torque ration prediction. From analysis of covariance (ANCOVA) the mean effect of travel speed, tyre inflation pressure and wheel numeric on tyre net traction ratio were found to be highly significant, while the interaction of inflation pressure and wheel numeric was not significant. The 193 kPa inflation pressure was found the best, among the three inflation pressures used, in getting higher net traction ratio and higher maximum efficiency. Finally, two models were formulated for tyre net traction ratio; one in terms of wheel numeric and travel speed reduction and the other in terms of mobility number and travel reduction, to describe the tested tyre performance at different soil strengths.

novel data acquisition and differential global positioning system has been successfully integrated on-board a Massey Ferguson 3060 agricultural tractor for mapping tractorimplement performance with its geographical location. Both commercial and specially developed transducers were incorporated into the system for the needed tractor-implement performance measurements. Transducers were developed to measure drawbar pull at the tractor drawbar point, wheel torques and theoretical speeds at both tractor rear drive wheels, PTO torque at the tractor PTO output, forces at the tractor three-point linkages, and tillage depth at the tractor rockshaft. This complete and integrated system is capable of measuring, displaying and recording in real-time among others, tractor's theoretical travel speed, actual travel speed, fuel consumption rate, rear drive wheel slippage, rear drive wheel torque, pitch and row angles, and also implement's PTO torque, drawbar force, three-point hitch forces, and tillage depth. With the added differential Global Position System (DGPS) option, the system could be used for spatial mapping of the tractor-implement field performances. Under such configuration, the complete system is capable of measuring, displaying, and recording in real-time tractor-implement's geo-position in the field with respect to its measured performance. Static calibration tests on various associated transducers for the required measurements showed excellent linearity with correlation coefficients that are closed to 1.The developed system has been extensively and successfully field demonstrated for spatial mapping of tractor-implement field performance with a mounted disk plow on Serdang Series sandy clay loam soil.

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