16 Feb 2003, 07:57, JEAN PARROT (1:123/140), wrote to MATT MC_CARTHY:

Hi JEAN.

 MM>> There were no thrust bearings that could withstand the end thrust 
 MM>> of single-angled gears for the duration of a trans-oceanic 
 MM>> crossing.

 JP>         I would like to see how this is done. I am trying to 
 JP> visualize this. I thought that most large ship had a straight out 
 JP> drive to the prop. The diesel maybe as they turn over at very low 
 JP> rpm but I can see where a turbine would need a step down box. The 
 JP> larger the prop the slower it turns.

AFAIK, the newer ship engines no longer shut down and start up 'backwards'
for reverse.  That's at least one place the gears are used.  Next, as you
stated, is matching the engine's optimal speed to the correct prop speed.
Too slow a prop and you only stir the water, too fast and you have a
teriffic amount of friction against those hugh blades, either of which
costs extra fuel.  The ratio on the marine units is usually very close, ie:
1.2 to 1, 1.1 to 1, etc.  Don't believe I've seen any greater than 1.5 to
1, and that was in very small stuff like tugboats.

I also saw lots of them in the 'junkyards' in Vietnam, and I believe they
were used in the main gear boxes on the UH-1Bs.  


     Good luck...  M.

--- Msged/386 TE 06 (pre)