In this paper the results of a project funded by Regione Toscana aimed at reducing the power absorption of auxiliary devices in vehicles are presented. In particular the design. testing and application of a magnetorheological clutch (MR) is proposed. aimed at disengaging the vacuum pump. https://www.roneverhart.com/Western-Digital-Ultrastar-DC-HC570-WUH722222ALE6L4-0F48155-22TB-7-2K-RPM-SATA-6Gb-s-512e-SE-3-5in-Refurbished-HDD/