BLOCK-MOUNTING 8N3052 - Caterpillar

Supplemental Steering
Many machines have a supplemental steering attachment that can operate the steering cylinders when the wheels turn (machine not stopped) if either the engine stops or hydraulic pump (26) has a failure.
FRONT OF DIFFERENTIAL CASE AND FRAME
7. Diverter valve. 19. Supplemental steering pump.Supplemental steering pump (19) is a two-section pump that has diverter valve (7) combined with it. The pump is fastened to the front of the differential case and frame. Pump (19) is driven by the ring gear of the differential when the wheels turn. When the wheels turn supplemental steering pump (19), oil goes into the steering hydraulic system. The oil output from the supplemental steering pump adds to the output from hydraulic pump (26).Hydraulic pump (26), on machines without the supplemental steering attachment, has approximately 20 U.S. gpm (76 liter/min) more output than the hydraulic pump used on machines with supplemental steering.Two check valves (13) and (25), one on the output side of pump (26) and one on the output side of supplemental steering pump (19), are other parts of the supplemental steering attachment. The oil from supplemental steering pump (19) always goes through check valve (13) but can not go through check valve (25), if there is a failure in either the pump or the engine.When the speed of the machine is less than 15 mph (25 km/hr) the output from both pump sections goes through check valve (13) into steering control valve (16). When the speed of the machine is between 15 and 20 mph (24 and 32 km/hr), diverter valve (7) lets the output from the large pump section go back to the pump inlet of the valve and only the output from the small pump section goes to steering control valve (16).The amount of oil from supplemental steering pump (19) is in a relation with the rpm of the machine drive wheels. When the rpm of the machine drive wheels decreases, the output of oil from pump (19) is less and steering cylinders (14) and (20) move slower. When the machine goes slower, less mph (km/hr), it takes longer for the machine to make a turn.Steering Control Valve
Hold Position
When there is no force on the steering wheel, spring (11) in the steering control valve keeps valve spool (9) in the HOLD position (H).The oil from the hydraulic pump goes in the control valve through inlet passage (5). The pump oil goes in flow control valve (4) and there is an increase of oil pressure. The pressure of the oil moves flow control valve (4). The position of valve (4) now lets the pump oil go through holes in the valve into passage (13), through a passage in the control valve into passage (6). The oil also goes through outlet (3) to the supply tank.A small amount of oil in passages (13) and (6) goes through slots (12) and (17), in valve spool (9), into passages (15) and (16) to the steering cylinders. The low pressure of the oil in each