Repair and Maintenance Cost Models for Tractors in Saudi Arabia

[A.T.C.: accumulated repair and maintenance cost, a, ~: constants, N: independent variable (accumulated operating hours or ratio of actual tractor age to expected life)]. The general model using the ratio of actual tractor age to expected life showed better accuracy (R2=0.715). The tractors classified to two groups, according to their operating age, one with tractors used under 6 years, and another used over 6 years. The cost-estimate model developed for the first group was based on accumulated operating hours, but for the second group the model was improved when The objective of this study was to develop tractor repairs and maintenance cost models using complete and accurate records of 40 tractors of Hail Agricultural Development Company (HADCO) for a period of five years. Six models were developed having the following form: the ratio of tractor age to its expected life was used. This could be explained when the tractor is new, the costs is low while increasing when the tractor getting older and major maintenance is needed. Tractor repair and maintenance models were developed based on tractor power. It was found that the developed models based on the ratio of the tractor age to its expected life either for tractors with 100 kW gave better estimates. But the comparison between the models of the two groups showed that big tractors have better distribution of repair and maintenance costs than smaller tractors. Comparison of this study with the similar studies showed that the cost of repair and maintenance in this study was lower than those of other studies. One of the reasons is that the data were collected from one huge project which kept excellent records of each single work done for each tractor. Beside good management of all the project inputs. It is recommended that the use of mathematical models developed for tractor repair and maintenance be used to those conditions for which they were developed for, or very similar in costs of spare parts and labor