Jim Dunmyer said the following to Mike Ross on the subject of
RE: ENGINE DESIGN (28 Oct 97  07:24:45)
 >> Yes, I agree and most use electric drive to transfer power to the prop.
 >JD> They do? Do you mean outside of submarines?
 > Yes, the turbo-electric drive. First adopted in the USA in 1908. The
 > main driving power is transferred magnetically across large air gaps.
 > Most warships of the 50's employed the system. The magnetic medium can
 > absorb shocks and is a simple reliable speed reduction without gears.
 > Nothing new here, trains use diesel-electric drive. Similar idea.
 JD> I'd sure like to see how a magnetic coupling can 'reduce speed without
 JD> gears'.  Do you have for-sure knowlege of ship drivelines made as you
 JD> describe?
Both mechanical and electric type gearing are commonly used on ships.
Electric seems to be favoured over mechanical for the largest ships.
The larger passenger liners used it.
The earliest reference I have found for the US Navy is the aircraft
carrier Langley (20,000 tons). It was originally an experimental ship
used to test the electric drive system. In it steam turbines generated
the electric current to drive the props.
They were very successful tests and it was then used in their largest
battleships. However, mechanical gearing was retained for cruisers and
destroyers of the time.
Well, I hope Alec would jump in. He's the marine engine expert here.
I'm writing this by rote so it may not be as detailed as should be.
 Mike
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