The Lex and the Sara

[Chiteng]

Does anyone know why the 'experiment' of electrical motors
being used to propel ships was abandoned after these two ships?

Seems to me that it would be inherently easier to use
electrical propulsion.

So what was the real deal?

[Nikademus]

Turbo-electric drive brought forth some advantages, primarily the ability to break up the powerplant by extensive sub-division, and the ability to quickly shift from forward propulsion to reverse and at the same speeds.

However TE drive was also bulky and heavy, potentially hazardous to operate around in wet conditions, and vulnerable to shock damage as demonstrated by Sara's torpedoing.

Advances in propulsion technology in the 30's also led to far more lightweight and efficient traditional propulsion systems which gave US designers, constrained by treaty restrictions and wanting to spend displacement on other aspects of the warship design spectrum, a key edge in ship building designs by the dawn of WWII.

[showboat1]

Wasn't TE drive used in the Nevada class? Wasn't that one of the factors, extensive damage and old-age being the other, that they didn't attempt to return Oklahoma to service.

Yeah, Sara suffered heavily, twice, from shock damage.

[Nikademus]

no, Nevada employed Turbines vs the old Triple expansion recipricating machinary of older USN BB's (North Dakota the exeption being the first experimental platform for BB housed turbine assemblies)

Because at the time, speed and reliability between the two systems were competetive (with the first US turbines having to be replaced in a reletively short period of time) recipricating machinery was preferred by some because it offered better fuel economy than the early turbines. (even back then, the General Board was always mindful of the Pacific and the ranges it would be required to steam)

So Nevada came equiped with turbines and Oklahoma had the traditional recipricating engines. (rebuilt with turbines during the late 20's reconstruction/modernization

Oklahoma was not returned to service because by the time she was rightened and refoated (an amazing engineering feat) it was late in the war and her value vs the cost of rebuilding was such that it was not deemed worth the time and cost (sadly)

Then again....she escaped the fate of the scrapers.

[LTCMTS]

Actually, while the original rebuild program for the coal burning ships of the US battleline included TE machinery left over from the South Dakotas, financial restrictions meant that only the boilers were replaced, including the Nevadas and Pennsylvanias. The TE power plant would have given 60,000hp, with the plant rated for normal operations at 40,000hp. This would have given the Utah, Florida, Arkanasa, Wyoming, New York, Texas, Nevada, and Oklahoma around 23-24 kts top trials speeds.
In any case, the reciprocating plant was never replaced in the Oklahoma, leaving her top trials speed at battle displacement at 19kts. Nevada was limited to 20kts, meaning the US battleline was not a 21kt force, but a 19kt force facing a 24kt force.
Oh, and the Saratoga also had a problem with her ring distribution system circuit breakers popping under shock from torpedo hits.

[LTCMTS]

USN DE's were also built with TE plants. Turbines need geared reduction boxes to efficiently propel ships. Gear production was one of the industry's most high tolerence technologies. It proved to be a bottle neck in ship production which is why PFs and merchant ships were built with recipricating machinery, CVEs and DE's with diesels and DE's with diesel-electric propulsion designed for subs. Since the speed of the motors can be controlled to the most efficient RPM for the propellers, while the turbines are run at their most efficient RPMs, you avoid the need for reduction gears, which do the same job mechanically. As a further aside, the USN was the only one to use diesel-electric propulsion, allowing smooth selelction of the optimum shaft rotation for efficient cruise speeds, while also charging the batteries, something the straight diesel plants in foreign subs could not do. Foreign subs could run on the surface or charge their batteries, not both, unless they carried small diesel motors to charge the batteries seperately.