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#152440 - 04/08/05 07:30 AM U.S.S. Tennessee -- Electric Propulsion
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Thanks to Alan Belson for the following.


Other sites featuring details of this magnificent ship.

This latter has a graphic description of "USS Tennessee" in action at Pearl Harbor.

The USS Tennessee was launched on April 13 1920, and featured all electric drive. While the websites I've visited concentrate on her service before, in and after WWII; how she survived action at Pearl Harbor, her service life and her eventual fate, there is no data on her electric propulsion system.


USS Tennessee's electric propulsion consisted, at commissioning, of two 16000 hp double-flow impulse steam-turbines, each driving, at 2075 rpm, a 13,250 kva 2 pole 3270 volt 3 phase alternator, as prime movers. Four propeller-motors were used, each being wound for both 36 and 24 poles and giving an output of 7000hp at 170rpm or 2125hp at 118rpm.

Photographs Nos 2 and 3 show a main motor stator before winding, and a finished main motor rotor. Rotors had a three-phase windings and slip rings.

USS Tennesee used liquid rheostats of the weir type for manoevering, (this is a type of rheostat where a plate (or plates) is lowered into an electolyte, usually a sodium hydroxide solution, the electrical resistance decreasing as the area submerged increases). These rheostats were water-cooled.

The motor air-gap was only 0.12", and forced ventilation was provided by two separate motorised fans to each main motor, each fan supplying 10,000 cu ft of air per minute. This was in addition to fans on the rotors. Each stator had six thermocouples built into the windings, with the indicating instruments in the control room, as shown in Photograph No 4.

As can be seen, all controls were operated by levers from a central position. Pole change switchgear was oil-immersed and mechanically interlocked. At overload condition (ie. at battle-stations), the whole equipment was designed to produce 33,500* shaft hp at 180 rpm.

nb. *Websites quote 26,800 shaft hp, but this was her standard rated output.

Normal alternators were used, insulated mainly with mica, in order to avoid problems due to sea-water salts. One of these may be seen in the course of winding in Photograph No 1. Steam connections were provided to smother any alternator fires, and so the air ventilation was able to be an open-circuit design. Again, thermocouples were fitted in the windings for temperature monitoring.

Tennessee had eight oil-fired Babcock and Wilcox boilers, giving 334,144 sq. feet of heating surface, exclusive of the superheaters, for which I have, unfortunately, no data.

At full speed, 21 knots was attained.

For ships, within certain limits, speed is proportional to screw rpm, and the power required will vary as the cube of the revolutions. From this it can be shown that a ship can proceed at about 80% of her normal speed with only half her normal power. This turned out to be a favorable condition for electric drive, as duplicated generators and motors could drive the ship effectively even if entire drive trains were put out of action. Or again, Tennessee could proceed at over 13 knots with only one motor/alternator working, assuming one turbine and a couple of boilers were still running.

Auxiliary power for ships is roughly the same at sea as in harbor. Tennessee had 1800kw of auxiliary power, with six 300kw turbo-generators, more than was usually fitted to ocean liners of the period. One of these exploded on Tennessee at New York on 30 October 1920, injuring 2 men. The turbine was wrecked.

Tennessee was refitted after Pearl Harbor, and was finally sold on July 16 1959 and broken up for scrap.


Alan Belson
Mayenne, France
8th April 2005


One of the Main Alternators of USS Tennessee in the course of winding.


An unwound motor stator for USS Tennessee.


A completed Motor Rotor for USS Tennessee.


Starting Platform or Control Room of Propelling Machinery, USS Tennessee.

[This message has been edited by pauluk (edited 04-08-2005).]

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#152441 - 04/08/05 06:18 PM Re: U.S.S. Tennessee -- Electric Propulsion
NumberSix Offline
Junior Member

Registered: 03/19/05
Posts: 7
Loc: Burlington, Iowa
That is cool.

#152442 - 04/21/05 04:57 AM Re: U.S.S. Tennessee -- Electric Propulsion
Trumpy Offline


Registered: 07/05/02
Posts: 8532
Loc: SI,New Zealand
That's amazing Alan,
Thanks for the story and the pictures!.
Let's face it, these days if you're not young, you're old - Red Green grin

#152443 - 04/21/05 07:36 AM Re: U.S.S. Tennessee -- Electric Propulsion
Alan Belson Offline

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
Thanks Trumpy, but all praises are due to the original writer and photographer- I was only the mail-man, ( often am- most of my info. comes off the Net!). I only wish she could have been saved- but we can't preserve everything from the past, we have to move on. But the legendary USS Missouri (Mighty Mo) has been superbly preserved at Pearl, the cruiser HMS Belfast is on the Thames in London, and the tiny HMS Victory, (from the Battle of Trafalgar, 1805) is now lying at Portsmouth. As the car-ferry eases up the Solent past the forts into 'Pompey', I often gaze across at Victory sleeping at her mooring, and think of all those long-dead, but remembered, craftsmen lovingly hewing her from hearts of oak. It's not just nostalgia- every day our history is being formed, and just as fast destroyed. Take those totally stunning photos of E57's work recently posted -'gobsmacked' was an understatement, there is something else there, not just a 'job' - compare those to some of the so-called 'Conceptual Art' of today! 'A thing of beauty is a joy forever', and we're lucky now that digital-photography can preserve better the skills and sheer artistry of the crafts, those things which must eventually be scrapped when their usefull purpose has been served.
Wood work but can't!

#152444 - 04/22/05 03:47 AM Re: U.S.S. Tennessee -- Electric Propulsion
Alan Belson Offline

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
Info on HMS Victory, (still commissioned as a flagship in the Royal Navy), and HMS Warrior, which is anchored about 1/4 mile up the wharf.
Wood work but can't!


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