Abstract: On a mobile agricultural sprinkler of the type provided with a wheeled chassis and a rotatable winding member about which one end of a flexible tension member is wound and further including coupling structure thereon for coupling to a high pressure water hose as well as a fluid motor having a fluid inlet coupled to the coupling structure and a rotary mechanical output member, flexible torque transfer structure is provided for drivingly coupling the rotatable output member to the winding drum and is flexive under the transmission of torque from the output member through the torque transfer structure to the winding member. Wheel brake structure is also provided and operative to releasably brake at least one of the supportive wheels of the irrigation device. Also, the wheel brake structure includes fluid pressure actuatable operator structure shiftable between active and inactive positions and a fluid pressure line extends from the coupler structure to the brake operator for actuation thereof.