For an idea of how the single-ram system works, refer to figure 2-6 and note what happens during a starboard  turn.  From  the  helm  on  the  bridge,  movement is transferred electrically to the receiving unit in after steering, where the electrical signal is converted to a mechanical  signal.  The  receiving  unit  sends  the mechanical signal to the running pump, and the pump proceeds to pump oil to the port cylinder. Oil, at the same time, is taken from the starboard cylinder by the pump's suction. As oil is pumped into the port cylinder, the  ram  is  moved  toward  the  starboard  side,  turning  the rudder as it moves. The ram is forced toward the starboard  side  until  the  correct  rudder  position  is obtained, at which time the follow-up shaft causes the pumping  to  cease. Emergency  Steering  Gear On  ships  equipped  with  electromechanical  steering gear,  the  old-fashioned,  hand-operated  steering  wheel  is about  the  only  recourse  if  the  primary  mechanism  fails. On some small ships, a yoke can be fitted over the rudder head, and the rudder can be turned with a block and tackle. Electrohydraulic steering gear usually is provided with a standby pumping unit for emergency use. It is composed of a pump and an electric motor, identical to those shown in figure 2-6. If the steering engine being employed has a casualty, the six-way pump transfer cock is adjusted to align the ram with the standby pumping unit; the power is turned on in the standby unit; and  steering  is  transferred  over  to  the  standby  unit. Emergency  steering  for  destroyers  also  uses  the trick wheel, shown in figure 2-6. If a steering signal failure  occurs  between  the  steering  wheel  on  the  bridge and  the  receiving  unit,  the  helmsman  standing  watch  in after steering operates the trick wheel and receives steering orders on the sound-powered telephone. Should a power failure occur in steering aft, the rudder is moved by  disengaging  the  running  electric  motor,  and hand-pumping oil to the ram by means of a handcrank. This procedure is very slow. The rudder turns only a small  amount  for  every  revolution  of  the  crank. Steering Engine Cutout A safety device is installed on every steering engine. This safety device stops rudder movement when the rudder is brought against the stops. The limit most rudders can be turned is 35° to either side of center. Full rudder on most ships is 30° right or left; the extra 5° is applied only in emergencies. Unless you are ordered to do so, never put the rudder hard over. It is possible for the rudder to jam against the stops, causing you to make circles  in  the  ocean. Rudder Every ship is provided with a rudder located aft. When the rudder is set at an angle on a moving ship, a high-pressure area builds on the leading surface, and a low-pressure area forms on the trailing surface. Thus the water, through this difference in pressure areas, exerts a force against the leading surface of the rudder, which in turn forces the stem in the direction opposite that which the rudder is set. When the helm on an oldtime ship was moved athwartships across the deck, the rudder motion was in the opposite direction. The result was that the ship's head would go in the direction opposite that in which the helm was moved, and this still is true of any small craft steered with a tiller. On all ships equipped with steering wheels, however, the wheel, rudder, and ship's head all move in the same direction. That is, when you turn the wheel to port, the rudder goes to port, and the ship makes its turn to port. Remember, though, that the ship begins its port turn by sending its stem to starboard. The more headway a ship has, the more water piles up against the rudder under the counter, and the quicker the stem is pushed off. Consequently, a ship always turns faster and answers its rudder sooner at high speeds than at low speeds. Also, a greater angle on the rudder is required to turn a ship moving slow than one moving fast. STEERING  STATIONS When a ship goes into action, no one knows where it might be hit. If a ship has only a single steering station, a hit there would put it out of the fight. For this reason, a combat ship has more than one steering station so that control can be shifted almost instantaneously to any station. A destroyer, for instance, may be steered from the bridge, after steering, or the steering engineroom. Some ships have fewer steering stations, but every ship has at least  two. RUDDER  ANGLE  INDICATOR The instrument above and forward of the wheel angle   indicator   is   the   rudder   angle   order indicator-transmitter (fig. 2-7). This instrument has a dual purpose. During normal steering situations, it shows the actual angle of the rudder, which usually lags the wheel angle indicator by about 2° because of the time required for the steering mechanism to operate. For emergency steering, this instrument becomes useful in transmitting visual orders to the helmsman in after steering. By operation of the control knob, the rudder order is displayed on the instrument when the pointer 2-6