Abstract: A hinge/building system can be easily assembled/disassembled to create numerous layouts of interlocking and pivoting walls/accessories for use as children toys, commercial purposes (e.g., office cubicles, display units, model making), and residential purposes (e.g., changing rooms, shelters, shelves, storage devices). The system includes a plurality of panels connected with at least two clips and a rod. The clips include a cavity (sized to accept the rod) and at least two arms defining a channel sized to accept the edge of a panel. The clips and panels each include an engagement device such as a groove and tab. Clips can be repositioned on a panel edge to accommodate the clips on any other panel edge when assembled with the rod.

Abstract: A rear wheel drive vehicle is converted to a four-wheel drive vehicle by operation of a hydraulically operated clutch which is controlled by a hydraulic valve. The hydraulic valve is spring biased to a clutch disengaged position and is hydraulically actuated to its clutch engaged position through operation of a pilot valve circuit which includes an electrically operated solenoid valve. The pilot valve circuit includes a flow restrictor providing modulated flow thereby affording a controlled pressure rise in the clutch whereby a smooth engagement of the front wheel drive is achieved.

Abstract: A pressure responsive relief valve closing responsive to clutch actuating pressure and opening responsive to centrifugal forces and a spring force to relieve residual pressure in the hydraulic actuator of a rotating clutch to avoid clutch drag.