The presented, approach, and ductivity, but also to othe,r machines and facilities. The production anduse of cars is a simple example of this: tts—manufacturing costs, operationalcosts, and idle-time costs—apply. As for the idle-time cost: cars and tractors are acquired for a certain purpose.Let us compll of them are only factors of the idle-time cost, as in the case of a breakdown,a car of the same category will be rented. In the simplest variant, the cost of renting a similar carfor the carrying out maintenance work, or repairs can be used in the calculations. That is why the moreimportant the problem and the higher the idle-time cost the more reliable the machine that is required.Much better guides from the point of view of considering the cost components, including tractors, areincluded in the work published in 1997 by Kansas State University [3]. This publication represents adetailed practical guide on similar calculations and includes much reference data. Similar approaches forestimating the owners, in a briefer and more, pragmatic publication of the Universityof South Dakota [5], and some other specialist publications in the foreign agricultural business. Thus, thedefinition of some important calculation components of the efficient reliability level can be based only onthe results of forecasting the change in the engineering and economic characteristics of a machine usedfor a long period [3–5].The aim of purchasing any object is the efficient implementation of its consumer properties. The maintainabilityindicators of the machine-tractor units are considered to be most important for agriculturalenterprises, taking into account the strict requirements on the duration and quality of the performance ofengineering pn the reliability of the performance of the mechanical engineering process is estimated:the level of the factory reliability of used tractors (ϕ = 0.82) and the maintenance (ϕ = 0.76) and repair(ϕ = 0.67) quality. Let us further consider the mentioned weightiest components.The process of manufacturing tractors should provide for its regulation to ensure the specified level offactory reliabilitycturing. Moreover, the costs for keeping tractors in working order during operationare reduced. The contradictory character of these costs makes it possible to optimize the reliabilitylevel of the tractors. The dependence of the production cost of the tractor Cdependence on the levelof the factory dependability expressed by the time to failure of the 3rd complexity group P0, is graphicallyshown in Fig. 1.In the example illustrated in Figs. 1 and 2, the following is predetermined: Pnominal = 400 machinehours; Сnominal = 4 million rubles; С1 = 3 million rubles; С2 = 10 million rubles; = 100 machine hours;and P0max = 1000 mach–5 machine hours/million rubles2; we substitute into formula (5) and obtainthe dependence of the tractor cost on the level of the time to failure of the 3rd complexity group:4.8–5.1 million rubles) according to formula (6); it shos the point at which dependences (5)and (7) cross (Figs. 2, 3). The reasonable costs for keeping it in work order CRMA defined according to formula(7) amount to 48–5.1 million rubles with capital repairs taking place every τ = 4.5 years. For example,today the dependability es. Increasing the dependability level by 100 machine hours, the productioncosts increase by 355000 rubles. However, the costs for keeping a tractor in working orderdecrease by 595000 rubles; thus, there is a saving in costs of 240000 rubles per tractor. If the tractor productioncosts are decreased to 3 million rubles, its time to failure will decrease to 100 machine hours, andthe costs for repair and maintenance will grow to 8 million rubles; thus, there will be no point in purchasingthe tractor, as a tractor produced at a cost of 3 million rubles will require additional costs of 8 millionrubles during operation.where T is the time to failure, machine hours; S is total operating unit man-hours of maintenance andrepair, man-hour/unit; tА is the agrotechnical (optimal) duration of the operation, h; tclearance is the durationof the machine’s idle-time while the effects of a fault are resolved, h; tmaintenance is time used for maintenanceoperations within the operating cycles, h; Kuptime is the uptime coefficient; А is the scope of work,ha; n is the number (of units), pc.; W is the unit capacity, ha/h; ΔtMTU is the reduction in duration of theunit idle-time during the resolution of faults due to the use of the machine-tractor unit, h; Δtpreprocess is thereduction in the time consumption for keeping a machine in working order during the operating periodwhere Creg is the cost of the harvest lost per hour of idle-time of a machine-tractor unit depending on thefield work period; is the time required to eliminate the effects from a fault of the ith complexity group,h; torganizational are the idle-times due to organizational reasons during the elimination of the effects of a failure(search for spare parts, delivery, etc.), h; and yi is the fraction of failures of the ith complexity group ofthe talysis of the target functions based on the given indicators made it possible to state that the reasonableindicator of the time to failure of the 3rd complexity group for agricultural tractors of the 5th–8th drawbar category based on the components of the costs for manufacturing and maintaining them inworking order should be within the range of 600–650 machine hours. When used in plant growing, takingthe component of the losses of products into account, this should be increased to 840–890 machinehours. Doubls the original cost of the purchasing a tractor for the agricultural enterprise by a factor of1.3. However, the total costs and damages from the plant product losses over ten years of use will decreaseby 3 million rubles with the corresponding repair and maintenance costs of 670000 to 510000 rublesper year.The experimental studies were carried out to confirm the theoretical interrelations. Their most importantaspect was the necessity to select tractors with identical parameters (drawbar category, capacity, etc.)of at least two brands with the reliability and price indicators intentionally selected to be different. Besides,in order to minimize the influence of the other factors, these tractors should be used in identical conditions,i.e., in the same household and for the same type of work. Thirty-one tractors were observed duringthe experimental study, including 11 K-744 P2 and 12 Buhler-Versatile 2375 tractors. Each tractor wasmanufactured in a different year and 2–6 tractors were acquired per year. The K-744 P2 tractors were usedfor a longer period of time of up to 7 years, while the Buhler-Versatile 2375 tractors were used for up to5 years. Even under the identical conditions of use, the average annual time to failure of the Buhler-Versatile2375-744 Р2 tractors (691 machine hours for 19 tractors). It follows from the experiments that thisindicator is defined by the reliability level of the tractors, as well as many other factors, including the performanceindicators of an agricultural machine together with a tractor and the conditions and arrangementof a machine-tractor unit’s use in a household (increased equipment capability, qualification of thespecialists, distribution by work type, etc.) [7].During the observations, the breakdowns in termsTractors with different reliability levels were compared based on the time to failure, without taking theyear of manufacmance, fuel consumption, and cost of the spare parts; the duration and labor intensityof maintaining them; and the elimination of faults. The results of the analysis of the experimental dataexpressed by the ranges of the indicators, respectively, for the K-744 Р2 and Buhler-Versatile 2375 tractorsand their comparison with the previously obtained theoretical dependences are presented in Fig. 6.The presented method of defining the reasonable reliability level of an object cannot be related to anyof the existing rely calculation [9] and methods of structural analysis [10]. It is probably worth studyingfurther as the reliability calculation method based on the cost criteria.The results of the study can be used by specialists at agricultural enterprises while upgrading theirmachine-tractor stocks, as well as by the departments responsible for the reliability of tractors at theplants, to estimate and analyze the dependability and maintainability of agricultural tractors within theirperiod of operation and resolve the problems of controlling their operational reliability during the productionstages. This approach can also be used to calculate reliability in other machine-producing spheres. Inthis case, the last component—the calculation of losses from the idle-times of an object during periodsrepair or maintenance—needs to be adapted.REFERENCES1. Arkhipov, V.S., The way to estimate bills for tractors lifetime, Traktory Sel’khozmashiny, 2014, no. 5, pp. 3–9.2. GOST (State Standard) no. 53056-2008: Agriculture Equipment. Methods for Economical Estimation, 2008.3. Kastens, T., Farm machinery cost calculations, Kansas State Agricultural Experiment Station and CooperativeExtension Service, May 1977, no. MF-2244.4. Edwards, W., Estimating Farm Machinery Costs, Iowa State Univ. http://www.extension.iastate.edu/agdm/crops/html/a3-29.html. Cited 07.01.2017.5. Dietmann, P., Figuring the cost to own and operate farm machinery, Univ. of Wisconsin. http://www.learningace.com/doc/4964167/7d9e6c1eb4e56b7a2a4b6b3f48696a0c/figuringthecosttoownandoperatefarm. Cited21.01.2017.6. Gulyarenko, A.A., Correlation between factory reliability and bills for supporting tractors operation ability incrop farming, Probl. Mashinostr. Avtomatiz., 2010, no. 4, pp. 111–113.7. Gulyarenko, A.A., Requirements for fail-safety and reparability of tractors used in crop farming in NorthernKazakhstan (by the example of 5-8 traction class tractors): grounding, Cand. Sci. (Techn.) Dissertation, Chelyabinsk:Chelyabinsk State Agroengineeing Academy, 2012.8. Grisso, R.D., et al., Using tractor test data for selecting farm tractors, Poqoprivredna Tehn., Agricult. Eng., 2012,vol. 1.9. Ryabinin, I.A., Logical and Probabilistic Analysis of the Problems of Reliability and Safety, Saarbrucken: PalmariumAcad. Publ., 2012.10. Gnedenko, B.V., Belyaev, Yu.K., and Solov’ev, A.D., Matematicheskie metody v teorii nadezhnosti. Osnovnyekharakteristiki nadezhnosti i ikh statisticheskii analiz (Mathematical Methods in Reliability Theory. The MainCharacteristics of Reliability and Their Statistical Analysis), Moscow: Nauka, 1965.
