both valves are operated together. This allows rapid shifting from the on-service pumping unit to the standby unit; it prevents lining up both pumps to the ram at the same  time.  The  hand  lever  is  usually  located  between the trick wheels. It has three positions marked  P, N, and S. P denotes the port pump is connected to the ram;  N denotes  neutral  (neither  pump  connected  to  the  ram); and S denotes  the  starboard  pump  is  connected  to  the ram. Also, the hand lever is usually connected to motor switches. This lets the operator connect the selected pump to the ram and start the pump drive motor in one quick operation. In most ships this valve is electrically controlled  by  the  motor  controller  and  by  pressure switches. Principles of Operation The on-service hydraulic pump is running at all times and is a constant-speed pump. Unless steering is actually taking place, the tilt box of the main hydraulic pump is at zero stroke, and no oil is being moved within the main system. The auxiliary pump provides control oil and supercharge flows for the system. To  understand  the  operation  of  the  pump,  let’s assume  that  a  steering  order  signal  comes  into  the differential control box. It can come from either the remote steering system in the ship’s wheelhouse or the trick wheel. The control box mechanically positions the tilt box of the main hydraulic pump to the required angle and  position. NOTE: Remember  that  direction  of  fluid  and  flow may be in either direction in a hydraulic speed gear. It depends on which way the tilt box is angled. For this reason, the constant-speed, unidirectional motor can be used to drive the main hydraulic pump. The pump will still  have  the  capability  to  drive  the  ram  in  either direction. With the main hydraulic pump now pumping fluid into one of the ram cylinders, the ram moves, moving the rudders. A rack and gear are attached to the rudder yoke between the rudder links. As the ram and the rudder move,  the  rack  gear  moves,  driving  the  follow-up  pinion gear.  The  pinions  drive  follow-up  shafts  that  feed  into the differential box. This feedback or servo system tells the differential control box when the steering operation is  complete.  As  the  ordered  rudder  angle  is  approached, the differential control box begins realigning the tilt box of the main hydraulic pump. By the time the desired rudder angle is reached, the tilt box is at zero stroke. This means that the ordered signal (from the pilot house or trick  wheel)  and  the  actual  signal  (from  the  follow-up shafts) are the same. If either of these change, the differential control box reacts accordingly; the main hydraulic unit pumps oil to one end or the other of the ram. The  trick  wheels  provide  local-hydraulic  control  of the steering system of the remote steering system fails. A  hand  pump  and  associated  service  lines  are  also provided  for  local-manual  operation  of  the  ram  if  both hydraulic  pump  units  fail. Operation and Maintenance The   Machinist’s   Mate   watch   stander   usually operates the steering equipment only in abnormal and emergency situations. For this reason, you should be thoroughly  familiar  with  all  emergency  procedures, such as local-hydraulic steering with the trick wheel and local-manual  steering  with  the  hand  pump.  Operating instructions and system diagrams are normally posted near the steering gear. The diagrams describe the various procedures and lineups for operation of the steering gear. Be sure that the standby equipment is ready for instant  use. General maintenance of the steering gear requires that you clean, inspect, and lubricate the mechanical parts and maintain the hydraulic oil at the proper level and purity. The Planned Maintenance System (PMS) lists the individual requirements for the equipment. The electricians  maintain  the  electrical  portion  of  the steering system, including the control system. ANCHOR WINDLASSES In  a  typical  electrohydraulic  mechanism,  one constant-speed   electric   motor   drives   two variable-stroke pumps through a coupling and reduction gear. Other installations include two motors, one for driving each pump. Each pump normally drives one wildcat.  However,  if  you  use  a  three-way  plug  cock-type valve, either pump may drive either of the two wildcats. The hydraulic motors drive the wildcat shafts with a multiple-spur gearing and a locking head. The locking head allows you to disconnect the wildcat shaft and permits  free  operation  of  the  wildcat,  as  when  dropping anchor. Each  windlass  pump  is  controlled  either  from  the weather deck or locally. The controls are handwheels on shafting  that  lead  to  the  pump  control.  The  hydraulic system requires your attention. Make sure the hydraulic system is always serviced with the specified type of clean oil. 10-43