The usage of high-speed electric machines (HSEM) has increased due to the performance gains over mechanical transmission. However, the permanent magnets (PM) used within the electromagnetic rotor have low tensile strength and are susceptible to failure. For high-speed applications, surface-mounted PM rotors are most suitable, consisting of three interfering components. Accurate mechanical analysis of the rotor is required to predict a successful rotor design. Generalised plane strain (GPS) theory has been developed for three-cylinder rotors and requires experimental validation. In this paper, a test rig and suitable rotor are successfully designed to experimentally verify the GPS theory, with reduced complexity when compared to those in existing literature. The test rig enables the use of digital image correlation (DIC) to analyse the rotor surface strain, requiring a rotor design that produced enough outer surface strain to be detected. The result can then be compared to the GPS theory prediction for validation.