On 12May2018 0506, Phil Pugliese (via tml list) wrote:

> According to several books I read some decades ago & as best I
> remember; When the USN began building Dreadnoughts it also began an
> evaluation of propulsion schemes by building pairs of ships (classes)
> w/ differing propulsion; #1 reciprocating vs turbine  (YES, the USN
> actually built early Dreadnaughts w/ reciprocating engines!)     the
> turbines won so;

Actually, early USN dreadnoughts were powered with reciprocating engines
for two reasons 1) The US industrial plant wasn't really up to making
turbines of the required power at that time, and 2) the turbines of the
time drove the propellers directly, and as turbines are very inefficient
at low speeds, turbine powered ships had poor cruising ranges and the
USN needed ships with lots of range (because even in the early 1900s
they expected any major war to be with Japan, and the US had no bases in
easy reach of the Western Pacific).

> #2 turbine vs turbine (2 competing turbine designs. I believe that
> one was named 'Parsons')     one design was selected & then;

Parsons was the British turbine design, and it won. Which was the better
choice was important because one (Parsons I think) was rather longer
than the other, so the choice had to be made before detailed design work
could begin.

 > #3
> conventional turbo propulsion vs turbo-electric The turbo-electric
> won out & all the later WWI-class BB's originally had turbo-electric
> propulsion.(I recall something about some thousands of volts of DC
> delivered to electric motors coupled to  the drive shafts) I believe
> that the turbo-electric was removed when the ships were overhauled
> later in their lives while the new designs drawn up in the '30's all
> had conventional turbo propulsion. I always wondered if the
> turbo-electric ships eventually displayed some sort of long-term
> problems, what with the omnipresent, corrosive seawater that they
> were constantly exposed to.

No more than steam lines do. The main advantage of turbo-electric
designs is that you can compartmentalise the ship much more, as the
turbines don't need to be near the shafts, and the motors can be much
further aft (which also allows shorter shafts). An other advantage was
that the turbines can always run at optimal speed, giving better economy
than ungeared turbines.

Turbo-electric plants for warships was killed by the naval treaties, as
they made weight into by far the most important consideration. By the
time that didn't matter any more as turbines with reduction gearing were
a mature technology and were very fuel-efficient.

--
Rupert Boleyn <xxxxxx@gmail.com>
Chief Assistant to the Assistant Chief