on-rail transfer trolleys with fixture cradle 75t-Perfect Transfer. US7591621B1 - Wind turbine blade transportation system. The rails 34, 36 are fabricated from 25-pound 6-Perfect Steerable Transfer Carth wide-flange (6wf25) mild steel beams, held together with mild steel end plates 50, 52, which also serve to retain the trolleys 40 on the rail.