A skid steer loader is a machine used in construction for multiple tasks. Its small size and versatility makesit a use-full addition to any work site. The machine is driven by a combustion engine that in turn powers ahydraulic pump. This hydraulic fluid from the pump is then directed to either motor to propel the vehicle. Twospeed motors are used to allow high-speed operation. A problem present in the current design of the hydraulicsystem for a skid steer loader is its tendency to jerk when shifting speed at low temperatures. In an effort toidentify potential problems and rectify those, two models will be constructed in Simulink. One is a model ofthe whole system, where the pump and both motors are included as well as the machine itself. The other modelis designed to predict the system behaviour of one motor and a pump in a flywheel test rig. Also auxiliarycomponents are included in the models, including the two-speed shifting valve and pressure release valves. Bothmodels will predict the system behaviour from a set of input variables, including temperature, oil viscosity andgeometrical parameters. Improvements to the design where identified by analysing the simulation data. It wasfound that system performance could be enhanced by switching to an alternative notch shape of the two-speedshifting valve.

Skid-steer loaders are also called mini loaders. Skid-steer loaders are capable of zero turning radiuses, which make them extremely maneuverable and suitable for confined spaces. The aim of this thesis study is to design the loader mechanism for skid-steer loaders. Primarily, the loader mechanism synthesis will be performed to determine the basic link dimensions for the mechanism of the loader. Genetic algorithm will be used in the design process. Besides, the hydraulic cylinders dimensions and working pressure of the loader mechanism will be chosen according to the forces that will be applied. After the link dimensions of the loader are determined, 3D modeling of the loader mechanism will be performed. Afterwards, the finite element analysis of the system will be carried out. Finally, improvements will be made on the model according to the results of the analysis.

The theme of this diploma thesis is design of skid steer loader with capacity up to 1 tonne. The result of this thesis is a conceptual solution of loader. It describes structural, technological, ergonomic and visual aspects with respect to current trends.

The object of this diploma thesis is revision of coolant system skid steer loaders “BOBEK” B861, B961 and his eventually optimization for prevention of overheating hydraulic system and engine. The first part dedicate of general issues of coolant skid steer loaders. The second part is the calculation during heat stress hydraulic systems of loader and the third part include proposals for solutions problems of overheating hydraulic systems and combustion engine.