The final thesis focuses on the hay crane arm. An electric hay crane is used in barns to transport forage from the warehouse to the place of consumption. The hay crane arm is the connecting link which enables adjustable reach through an extension system and transfers load from forks to the supporting structure of the crane. The thesis presents the operating conditions in which the arm will work, the solution concept and group classification according to the FEM 1.001 standard. The evaluation of the arm is in accordance with the standard and the solutions of the author can be seen in the enclosed technical documentation.