The aim of the study was to conduct an economic analysis of the possibilities of using photovoltaic (PV) installations in selected farms. Two selected online PV calculators were used for the analysis. The research included 15 farms located in the Małopolskie Province. For a PV installation estimated using Calculator 1, Hewalex, the payback period ranged from 5.5 to 7 years for the 40% subsidy option and from 9 to 11 years without the subsidy, respectively. On the other hand, the payback period estimated with the use of the SmartekDom calculator ranged from 6 to 8 years for the option with 40% subsidy. However, without the subsidy, the period ranged from 7 to even 13 years.

Objective: The objective of this study was to develop the load-carrying capacity models of tractor tires on the rigid surface for both, radial and bias tires. Material and Methods: In order to develop functions, two tire constructional variables (section width and overall diameter), inflation pressure, and forward speed for the load-carrying capacity model were considered. The models developed in the literature for the load-carrying capacity of tires on rigid and soil surfaces were built on some limited data and as a result of this, the predominant variable and contribution of other variables still remain unknown. This study has the widest range of tractor tire sizes (width and diameter). The load-carrying capacity models developed in this study were verified with the theoretical models and experimental measurement values in the literature. Results: As a result of the study, it was found that the appropriate mathematical models were in non-linear (power) form and the coefficient of determination of the models was greater than 0.95. Conclusion: The models were verified against published data in the literature and found that the predictions from the models are in good agreement with the measured values.

The objective of this study was to find out the effects of torque rise on lugging ability of tractors. In British terminology, torque rise refers to torque back-up or torque reserve. Torque rise is the amount of torque that the engine can produce above the manufacturers rated amount of torque. It is the percent increase in torque, from rated torque to peak torque. In order to meet the above objective, two tractor reports issued by Nebraska Tractor Test Laboratory were used. Powertrain schemas obtained from three different tractor manufacturers were used and the total transmission ratios from these schemas were calculated. The effect of torque rise on lugging ability of the two tractors with four different gear boxes was studied. From the study, it was concluded that higher torque rise enables the tractor to run in a wide range of torque and the gear box to be chosen should be such that it can match with the engine.

The objective of this study was to develop mathematical functions to predict deflection for radial and bias tires. In order to develop the models, the data were obtained from the tire manufacturing companies and organized in Excel first and then transferred to Minitab® for stepwise regression analysis. The variables considered in the study were inflation pressure, load and tire width and overall diameter. Tire width (w) and overall diameter (d) was considered in a multiplication form. The tire deflection models in two different form (linear and non-linear) were developed for both, radial and bias tires. The model selection was achieved by three different criteria and % differences between the measured and predicted data. Based on the results of applying model selection criteria, the models for radial and bias tire in non-linear form were found to be adequate for predicting the tire deflection. The results from the stepwise analysis indicated that the load on tire was the predominant variable in the models and made the highest contribution to the prediction functions. The developed models were verified against to published literature data and found a good agreement.

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