Figure 10-37.Electrohydraulic speed gear.
electrohydraulic steering gear is shown in figure 10-38.
It consists essentially of a ram unit and a power unit.
The ram unit (view A) is mounted athwartship and
consists of a single ram operated by opposed cylinders.
The ram is connected by links to the tillers of the twin
rudders. When oil pressure is applied to one end of the
operating cylinder, the ram moves, causing each rudder
to move along with it. Oil from the opposite end of the
cylinder is returned to the suction side of the main
hydraulic pump in the power unit.
The power unit (view B) consists of two
independent pumping systems. Two systems are used
for reliability. One pump can be operated while the other
is on standby.
E a c h p u m p i n g s y s t e m c o n s i s t s o f a
variable-delivery, axial-piston main pump and a
vane-type auxiliary pump. Both are driven by a single
electric motor through a flexible coupling. Each system
also includes a transfer valve with operating gear, relief
valves, a differential control box, and trick wheels. The
whole unit is mounted on a bedplate that serves as the
top of an oil reservoir. Steering power is taken from
either of the two independent pumping systems.
The pumps of the power unit are connected to the
ram cylinders by high-pressure piping. The two transfer
valves are placed in the piping system to allow for the
lineup of one pump to the ram cylinders with the other
pump isolated. A hand lever and mechanical link (not
shown) are connected to the two transfer valves so that