Drum (10) for manufacturing a tire blank, comprising a shaft, two flanges (14) movable in translation along the shaft, and means for supplying compressed air, each flange comprising at least one pneumatic effector (36). At least one flange comprises a first, radially internal ring (46) and a second, radially external ring (48) movable in rotation around the first ring by means of at least two airtight pivot connections (50), the rings and the pivot connections delimiting at least one sealed chamber (52), said flange comprising at least one first compressed-air circulation channel (54), a first section (56) of the first channel belonging to the first ring being connected at one of its ends to the sealed chamber, and a second section (58) of the first channel belonging to the second ring being connected at one of its ends to the sealed chamber.