Date: 23 July 2015 09h00 LT
Position: West India Dock
Update part 7: the gear reducer
Last week the gear reducer was hoisted out of the engine room for an overhaul. After 12 years and close to 30 000 operating hours it is in use of some proper maintenance.
Ships bigger than the Clipper don’t always need a gear reducer. They can harbor an engine big enough to create a lot of power and still have a low rotation count. A low rotation count is necessary for efficient propelling. When the rotation speed is to high the blades of the bow thruster don’t have enough grip on the water so to speak to propel the ship.
On board of the Clipper however, there is not enough room for such a big motor. That’s why she has a relatively small compact 4-stroke Caterpillar V8 cylinder motor. This motor can generates enough power (1000hp) but does this with 1800RPM. This amount of power is necessary when maneuvering, when the bow thruster is also used. The bow thruster also gets its power from the main engine through an hydraulic pump. 1800 RPM would be too much for the bow thruster. A RPM of 400 would be most efficient. This is where the gear reduce comes in. It is located between the motor and the bow thruster and reduces the amount of rotations to a more efficient volume. Also the gear reducer allows the bow thruster axis to be detached from the main engine. When sailing this reduced resistance. The bow thruster itself can be altered hydraulically in feathering position, further diminishing the resistance when sailing.
To overhaul the gear reducer it had to be lifted out of the Clipper. A hole of 180 cm x 180cm was made in the hull through which this 2 tons weighting piece of equipment was lifted. At first there was not enough maneuvering space in the engine room for the crane. By cutting the exhaust pipe of the main engine the necessary room was created. When, after the overhaul, the gear reducer has been put back in place, the exhaust will be repaired with detachable two flanges. This will ensure easy access in future.