Modeling of Repair and Maintenance Costs of 2WD Tractors in Iran

Machinery ownership and operating costs represent substantial portion of total production expenses. Ownership costs include charges for depreciation, interest of investment, taxes, insurance and housing facilities. Operating costs include repair and maintenance (R&M), i.e. spare-parts, wages and lubricants. R&M costs of machinery are those expenditures necessary to restore or maintain technical soundness and reliability of the machine. Accurate prediction of R&M costs trends is critical to determine optimum economical life of machine and to make appropriate decisions for machinery replacements, and also for general farm management purposes. Since variation in R&M costs depends on site and time specifications, a general relationship can not be suggested. But prediction of these costs at an acceptable level can be made by fitting a regression model based on the previous data. Also, great variations in R&M costs between different tractor models, tractors and their operating conditions make it difficult to obtain meaningful generalized models. The scope of this book is to model accumulated R&M costs based on accumulated usage hours for some two wheel drive tractor models in Iran.