Page 44: of Maritime Reporter Magazine (March 1997)

SPEED - RAMPED :pr pmoKj REFERENCE

RPM

READOUT

SHAFT

SPEED - . FEEDBACK

Figure 1 — Slip-system logic schematic shows what controls ahead and astern clutch- es in marine drive. to zero rpm. During the slip mode the engine remains at idle while the clutch is slipped to deliver the reduced propeller speed. When a pro- peller speed above engine idle speed is needed, the pilothouse control han- dle is moved forward and the slip- control system fully engages the clutch and the engine accelerates.

The slip-control system can be oper- ated indefinitely, without damage to

WHEN PUSH COMES TO SHOVE, HAVE A VIKING ON YOUR SIDE

Circle 220 on Reader Service Card

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The torque transmitted during the slip mode is accomplished by shear- ing the oil film between the clutch plates. The heat generated during the slip mode is carried away by the cooling oil as it passes through the clutch and then dissipates through the reduction gear heat exchanger.

Maintaining Control

The closed-loop slip is accomplished by a proportional-integral-derivative (PID) controller, which ensures that the selected propeller speed is main- tained regardless of wave, wake or current conditions. The controller compares the error between the oper- ator selected speed and true propeller speed, and adjusts the clutch hydraulic pressure as required through a proportional slip-control valve.

Figure 1 is a control logic schematic for the slip-control system. The pro- grammability of the PID controller allows for the slip-control system to be adjusted for each specific applica- tion. This ensures smooth, stable propeller shaft speed control no mat- ter how large or small the system masses and inertias may be. During sea trials the PID controller is pro- grammed to match the propulsion system to the vessel. A small, hand- held keypad is plugged into the PID controller program port, and the PID program values are entered. The keypad is removed once the system has been fine tuned.

Marine Drive Includes Propeller

Shaft Brake

The continuous-slip hydraulic clutch control system is available in

Falk's 3000 MRH marine reduction drive line. The Falk 3000 MRH marine drive incorporates surface hardened and ground gearing with internal hydraulic clutches. Also con- tained with the reduction gear is the oil cooled, air-actuated propeller shaft brake. The location of the inter- nal shaft brake greatly reduces the required shaft brake size since the brake is mounted on the end of the pinion shaft, taking advantage of the reduced shaft torque.

Figure 2 shows the orientation of the gearing in the Falk 3000 MRH marine reduction drive. The marine reduction drive contains two multi- disk, oil-sheer clutches, one for ahead mode operation and a second for astern mode operation. Either clutch can be designated as ahead or astern in order to yield the required pro- peller shaft rotation for each particu- lar application. Both hydraulic clutches are capable of unlimited con- tinuous slip at engine idle speed, and maximum torque transmission at full

Circle 225 on Reader Service Card 46 Maritime Reporter/Engineering News