Abstract: The flexible wheel is one among the most important components in a harmonic drive . Due to the complexity of forees acting on a flexible wheel there exists thus for no satisfactory procedare for its strength calculations . In the paper measurements for the dynamic stresses in the flexible wheel are described,with the purpose of contributing to the search for a rationale of flexible wheel design. Torsional breekage, at the bottom of a flexible wheel has been found in the experiment , such breakage being strongly influenced by the dimension of fastening and assembly stresses .