Cruise Training

May 14, 2004

The ship is a large classroom, it is a large hotel, and it is a large engine room.  In the engine room, we have all of the systems of a little city to keep our lives comfortable.  Then, we put all of this into a hull, lay it on its side, put a big engine into it and connect it by a shaft to a propeller an move it around. 

The propeller is a very unique part of the ship.  The Golden Bear only has one propeller (picture below).  It has a nineteen-foot diameter and a pitch of 17 plus feet.  The pitch means that every time it turn around once, the ship moves about 17 feet through the water.  We are currently moving at about 90 RPM, so the propeller turns around 90 times a minute or 5400 times and hour.   AT 17 feet each time, that is about 91,800 feet per hour.  If we divide by 6076 feet per nautical mile, we get about 15 nautical miles per hour.  That just happens to be how fast the ship goes at 90 RPM. 

A propeller the size of the Golden Bear’s is most efficient when it rotates between 80 and 140 RPM.  However, the main engine turns at about 400 RPM, much faster than you would want the propeller to turn.  With the use of a reduction gear (see diagram below), the rotation of the engine is reduced to the desired range. 

A shaft is connected to the propeller, and as the propeller turns, it provides thrust to the shaft.  The shaft cannot push against the reduction gear or the engine or it would distort the movement.  Thus, a thrust bearing (see diagram below) is designed to absorb the thrust and transfer it to the hull, and move the ship.

Picture of TSGB's propeller

Diagram 1.