Generally speaking, excessive side thrust and roller slippage are two different aspects affecting cam-roller mechanisms. In novel large-scale hydraulic drivetrains for offshore wind turbines, the highly dynamic nature of these mechanisms combined with the interplay of cyclic loads, frictional torques and inertia promote slippage at the cam-roller interface. At larger scales, the effects of roller inertia become much more pronounced, as the inertia escalates exponentially with the roller’s radius. This study presents a comparative analysis between radial and offset roller followers in novel large-scale hydraulic drivetrains, where offset followers are incorporated to minimize the side thrust. The framework encompasses a comprehensive kinematic and force analysis, to provide the inputs for two lubrication models integrated into the torque-balance equation, where the possibility of slippage is allowed. The findings reveal that the equivalent side thrust can be reduced by 51% with offset followers. Both configurations experience slippage during the low-load phase, but it rapidly diminishes during the high-load phase. This sudden transition in rolling conditions results in a sharp increase in surface temperature and traction force, emphasizing the importance of minimizing sliding at the interface. However, besides the substantial side thrust reduction, offset followers showed superior tribological performance, mitigating undesirable thermal and frictional effects.

Under real sea conditions, floating vertical-axis tidal current turbines experience motions in six degrees of freedom which impact the hydrodynamic performance. In this paper, a 2D free-wake vortex panel method (U2DiVA) is adopted as a time effective tool to assess the hydrodynamic response of an existing floating vertical-axis tidal turbine under platform’s surge motion in uniform tidal current. The results of the numerical simulations show that the surge motion modifies the flow field perceived at the blades, affecting the instantaneous value of the tip speed ratio and the time evolution of the induction field. Consequently, surge motion impacts on the structural strength of the turbine by introducing multiple frequencies of oscillation of the hydrodynamic coefficients and increasing the peak loading on the rotor. Surge motion is found to be beneficial to the average power extraction while only marginally affecting the mean loading. The preliminary findings of this research provide insights about critical aspects for the design and evaluation of floating vertical-axis tidal turbine systems.