# 1930s: German navy switchs to diesel power?



## tomo pauk (Nov 24, 2012)

German navy received, in 1930s, 'pocket battleships' that were powered by diesel engines. That practice was not followed in subsequent classes. Wonder if there is merit to apply diesel power (either full, or partial) in other KM ships, from destroyers up to battleships?


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## Shortround6 (Nov 24, 2012)

The light Cruisers had mixed power. Diesels on some shafts and Steam Turbines on others. Plans were made for Diesels in later ships that were never made.

State of art at the time was that diesels required more volume (hull space) that a steam turbine installation of equal power and many have been heavier. 









Boilers had made a lot of progress between 1916 and the early 30s. reducing the size and number of boilers needed. Power plant size helps govern hull size and in the case of armored ships, the size of the area that needs armor protection so a bulky power plant, even if economical ( and fuel oil can be but in double bottoms and used as part of the torpedo protection), may require a larger ship than a more compact but thirstier power plant.


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## Shortround6 (Nov 24, 2012)




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## tomo pauk (Nov 24, 2012)

Thanks for the feedback 

1: shafts
2: main diesel engines
3: reduction gears
4: diesel generators
5: chambers for 150mm ammunition
6: auxiliary diesel engines


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## davebender (Nov 24, 2012)

Diesel power would be technically interesting but it won't change the war. For that to happen German capital warships would need to leave port once in awhile to attack the enemy.


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## Readie (Dec 2, 2012)

Steam turbines were the power plant of choice.
Diesels did not have the power to shift WW2 battleships/ battle cruisers at 28 - 31 Knots.
I bet they were a sight at full chat...wow.
Cheers
John


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## davebender (Dec 3, 2012)

> Diesels did not have the power to shift WW2 battleships/ battle cruisers at 28 - 31 Knots.


That misses the point.

Diesels were very economical for cruising. WWII era surface warships typically cruised at 15 knots. Diesel(s) on the center shaft only need enough power for economical 15 knot cruise which constitutes about 95% of warship operations.

Steam turbines on the two outside shafts provide 30 knots or so for the 5% of operations when high speed is required.


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## Denniss (Dec 4, 2012)

This arrangement may be viable for three-shaft ships but RN usually had four-shaft capital ships.


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## Shortround6 (Dec 4, 2012)

The alternate power works up to a point. Battleships could need 20-30,000 more hp for an extra TWO knots. The difference between 28 and 30 or 30 and 32 knots. Even with Steam turbines there is a limit as to how much power you can put through each shaft (or through each propeller?). The Diesels need more foot print or volume per horsepower than steam turbines and battleship power plants were built "heavier" than cruiser power plants for both reliability and durability. Reliability for combat operations and durability because it is a much bigger project to replace battleship power plants. More decks and more armor have to be removed to get major power plant pieces into and out of the ship once it is built. Battle ships also have much heavier armor over the machinery spaces so an increase in power plant size causes a disproportionate increase in armor weight which causes the hull to be bigger to "float" the armor which requires more power for the same speed. 
As with many other things, technological advances came in fairly short order so comparing a 1950s ship to a 1930s ship (or engine) doesn't tell us much.


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## tomo pauk (Dec 4, 2012)

Was it a custom, in steam-powered ships, to install the diesel generators and/or auxiliary engines in the main boiler/turbine rooms, within the armored 'citadele'?


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## Readie (Dec 4, 2012)

Dave,
Diesels had their uses of course but, not as battle ship / battle cruiser main power units. Steam turbines were the most powerfull unit available whether maximum speed was used or not. 
The big change was from coal to oil as the boiler fuel.
Cheers
John


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## Shortround6 (Dec 4, 2012)

tomo pauk said:


> Was it a custom, in steam-powered ships, to install the diesel generators and/or auxiliary engines in the main boiler/turbine rooms, within the armored 'citadele'?



It depends on the ships, Most ships with an 'armored citadel' had the diesel generators and/or auxiliary engines within the citadel or at least the majority of them. In some ships they had their own compartments within the citadel, in others they were in the main machinery rooms. Some had a mixture. Some ships had some of their diesel generators outside the citadel, it depended on how "tight" the design was and/or if/when the electrical load changed during the design process. 
Battleships, in general, had much better sub division (more compartments) than cruisers. In some cruisers the main machinery compartments were _not_ sub divided side to side. That is to say an engine or boiler room extended from one side of the ship to the other because flooding just one side of the ship brought more danger of capsizing than the greater flooding but sinking on an even keel (little or no list to one side) that flooding the full width of the ship would bring.


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## Shortround6 (Dec 4, 2012)

Readie said:


> The big change was from coal to oil as the boiler fuel.
> 
> John



Other big changes were small tube boilers (less weight per ton of water turned to steam), Higher pressures and lots more super heat (some navies carried it too far) which also reduced the boiler weight per pound of steam. Together with the oil fuel it meant one big boiler could do the work of 3-4 smaller ones but be lighter and require much less crew. Throw in double reduction gear sets between the turbines and the props and the weight per HP of an early 1930s steam plant was waaaay lower than even a 1916/7 steam plant of the same power. AND more compact which means less armor. 

As far as speed goes please not that although there were other improvements the extra 4-5 knots that a Missouri had over a South Dakota were bought with most of the 10,000 ton and 200ft differences between the ships. Also please note that a Missouri was _supposed_ to be able to hit 27kts with only 1/2 of it's boilers lit. 

That is where the Diesel powered large warship runs into trouble. It cannot quite match the steam powered one in speed and that last 2-4knots require _so much_ weight and volume. If you think the Diesel powered ship can be slower and use it's guns/armor to fight it's way out of trouble that is a different argument.


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## Readie (Dec 4, 2012)

The armoured citadel must also include the magazine. No point in armour protecting the engines and not the magazine...look what happened to HMS Hood.
Speed was vital as it gave sea room to fight or run. Steam boilers pretty much reached the peak of their development as shown with locomotive technology in the Mallard.
Capital ships were not used lightly as the Germans showed with theirs. All much too much to risk?
The downfall of the capital ship was the aircraft but, that is another story.
Cheers
John


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## Shortround6 (Dec 4, 2012)

The Mallard was pretty much low tech. Try checking the British WW II Steam gun boats. 8000hp in a ship that weighed about what the Mallard and tender did. 

8000hp worth of WW II diesels that could run at that level for 8 hours or so at time would be a pretty complicated engine room. 

The Diesel powered American DEs had about 6000hp.


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## delcyros (Dec 4, 2012)

The biggest issue, and the prime reason for dropping Diesel propulsion from the german perspective was not the weight of the plant nor the spacial requirements for their installation (Diesels are rather compact compared to boilers). KM ship designing practice required excessive length of the waterline to be put under armour in the "armoured citadel", so both, armour weight and space are no issue here.
The reason for this was their desired protection scheme, moving from all-or-nothing alike Panzerschiffe with inclined main belts to a more sophisticated system incorperating belt and armoured slope + splinterbelt /ATB schemes to fit their specific anticipation of intended battle ranges. This system required a rather low placed main armour deck, which in it´s own required excess stability charackteristics to make worth the tradeoff in more appaerent risk of the flooding of it´s wingtanks through penetrations of the main belt. Their armour system was not to make these ships invulnerable but to keep the embedded vitals intact from even short range belt-penetrating fire. 
In order to attain large enough protected buoyancy and volume despite the low armour deck, the "armoured citadel" was taken intentionally further fore and aft than would be necessary. 
Thus, Diesels would indeed fit nicely their choice of armour protection philosophy.

Another problem is definition. When Germany signed AGNA 1935, it eventually was bound to the definition limits of Washington and London naval treaties. These treaties defined that fuel oil was not to be counted in standart displacement but all weight of the engine was. This is what eventually killed the Diesel choice. Diesel propulsion is MUCH more economical but You will require more dead weight buildt into the powerplant. Since the fuel weight doesn´t count but the machinery weight does, the choice of lightweighted, high pressure, superheated boilers and turbines was made.

You need to realize that Diesel propulsion was indeed always LIGHTER than boiler/turbine if You factor in the weight of fuel oils/diesel. The Panzerschiff DEUTSCHLAND had just 4,962 t of machinery and fuel weight for a plant capable of producing 54,000 SHP design and a max range of 10,000nm at 20 kts. SCHARNHORST´s weight was 9,990t (including fuel oil) for a plant capable of producing 134,000 SHP design but a max range of only 6600nm at 19 kts. Corrected for identic range, the machinery + fuel oil weight of SCHARNHORST would have to be drastically increased, to ~14,000t, resulting in a specific weight of ~104kg/SHP for steam turbine and 92kg/SHP for Diesel plant´s with a design range of 10,000nm @ 20 kts. 
Corrected for the higher (=134000 SHP) power of the SCHARNHORST´s, the DEUTSCHLAND´s plant (including Diesel fuel weight) would be 6,875t heavy, resulting in a specific weight of ~75kg/SHP for steam turbine and ~51kg/SHP for Diesel plant´s with a design range of 6,600nm @ 20 kts (same as SCHARNHORST). 

But since the Treaties are ignoring fuel oil weights, the lightweight advantage of Diesel is gone. On any Washington displacement, a Diesel driven variant will be correspondingly less powerful than a boiler/turbine driven one.

Mixed propulsion plants were tried in the various interwar CL but none actually worked well. Part of the problem is that You can´t run the boilers cold. Thus, they need to be lit up in order to have action reserve, meaning that in actual service condition in wartime a relatively high fuel consumption unaccounted for in peacetime has to be factored in.


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## Readie (Dec 5, 2012)

Shortround, We'll have to agree to differ about Mallard's tech spec being 'low tech', she was the first A4 to be fitted with a Kylchap double blast pipe and her WSR, which is held to this day, speaks for itself.
The steam gunboats were turbines not compound pistons. Great performers in heavy seas but, having to be kept 'in steam' was a disadvantage.
The British Gun Boats etc with 4 × Packard 4M 2500 petrol engines, total 5,000 hp went well but, the thought of sitting on all the petrol is eye watering....
A pretty explosive choice really....superheated steam or petrol.
Cheers
John


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## Shortround6 (Dec 5, 2012)

Readie said:


> Shortround, We'll have to agree to differ about Mallard's tech spec being 'low tech', she was the first A4 to be fitted with a Kylchap double blast pipe and her WSR, which is held to this day, speaks for itself.
> 
> John



The Mallard's WSR was a notable achievement but 250lb boiler pressure in a fire tube boiler, single expansion pistons and the rest of her "specs" were certainly not the latest word in steam power plants, either afloat or on land. Railroads were a world unto themselves and the steam plant had to survive extreme vibration and banging about which ship and stationary power plants (electrical generation) did not have to deal with. Attempts to use water tube (or flash in some cases) boilers at 300-600lb pressures in railway service were usually costly failures. Attempts to use geared turbines usually failed too, but that does not mean ship owners were going back to fire tube boilers and reciprocating steam engines for high powered ships in the 30s and 40s. 


Technology did not stand still and a 1928 Diesel installation may have been different than a 1938 Diesel installation. But steam technology was not standing still either. Late WW I technology required 8 oil fed boilers to produce 65,000hp on the last Hawkens class cruisers built. By the late 30s the twelve 6in gun cruisers were getting 80,000hp from just 4 boilers. In between 72,000hp was gotten from 6 boilers. Granted the later boilers may have been larger than the early boilers but 4 big boilers means fewer boiler rooms, less piping (fuel, feed water, and steam) and a more compact layout. Some Italian 10,000ton "treaty" cruisers were supposed to have 150,000hp. Try that one with Deutschland type diesels. 
US Baltimore class cruisers got 120,000hp from four boilers.


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## Readie (Dec 5, 2012)

Points taken SR but, the A4 was the last word in steam locomotive power and although steam lasted longer here than in the USA, no steam locomotive bettered Gresley's designs.
If you want the ultimately useful steam powered vessel, I would suggest these...warship: ww2 Liberty ship Specifications
Cheers
John


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## davebender (Dec 5, 2012)

When I was on U.S.S. America boilers were never completely cold when at sea. Only a couple minutes were required to bring an idle boiler into service. This sort of thing happened when an aircraft had a flap / slot problem that required a higher landing speed or more wind over the flight deck.

If the USN could find a solution I suspect other nations could also.


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## Readie (Dec 5, 2012)

davebender said:


> When I was on U.S.S. America boilers were never completely cold when at sea. Only a couple minutes were required to bring an idle boiler into service. This sort of thing happened when an aircraft had a flap / slot problem that required a higher landing speed or more wind over the flight deck.
> 
> If the USN could find a solution I suspect other nations could also.



There's a difference between 'cold' and 'not up to working pressure' with steam boilers dave.
I had a job on the MV Antonio de Satresqui, which was totally steam driven, winches you name it...fantastic relic to be on.
Cheers
John


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## Shortround6 (Dec 5, 2012)

Readie said:


> Points taken SR but, the A4 was the last word in steam locomotive power and although steam lasted longer here than in the USA, no steam locomotive bettered Gresley's designs.




Spoken like a true Englishman.  

Comparing British and American steam locomotives gets difficult because the Americans had larger loading gauges (height and width) and usually heavier rail which allowed for higher axle loading's. 

American coaches were also usually much heavier. 70-90 tons? Mallards record setting run with 7 coaches would have been the equivalent of 3 American coaches. 

Nothing can take away from the Mallard's record run but the title of "last word in steam locomotive power" has to at least consider the NYC Niagara class. Granted they were almost 10 years newer and twice the weight of a Mallard but their record stands almost alone (See Norfolk Western J class). 

NYC Niagara - Wikipedia, the free encyclopedia

to get back on topic railway practice and "high powered" ship practice began to separate back in the 1880s. Ships shifted to water tube boilers and not only compound expansion (used by a number of locomotives) but triple expansion (rarely, if ever, used successfully on a locomotive) and in some cases quadruple expansion. The Coming of turbines at about the turn of the century further separated the designs. Low powered ships continued to use reciprocating engines because they were cheap and relatively easy to build. 

Pre WW I it was common to separate destroyer engines/boilers from cruiser and battleship/dreadnought engines and boilers. Pre WW I destroyers were expected to be lightly built and their engines to suffer from breakdowns that would not be tolerated in a WW II destroyer. Their engines/boilers did offer a much better power to weight ratio than the larger ships. Reliability and durability was paid for in weight and volume. 
I believe there is even a design sketch for a Diesel installation for a dreadnought in the 1913 Brassey's annual. Theory was always ahead of practice  
Same volume mentions shaft turbines too.


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## Readie (Dec 6, 2012)

Shortround6 said:


> Spoken like a true Englishman.
> 
> Comparing British and American steam locomotives gets difficult because the Americans had larger loading gauges (height and width) and usually heavier rail which allowed for higher axle loading's.
> 
> ...




Not the Pennsylvania's K-4 Pacific SR? 
With US British steam locomotives its horses for courses rather like with cars and motorbikes. 

We had to keep steam going longer than planned as we were broke after WW2 and the money to invest in a new infrastructure locomotives etc simply wasn't there. I remember the steam hauled express from London to Plymouth and the smell of coal etc...but, when the new generation of diesels arrived and times were quicker that was more important than nostalgia.

Thanks for the information in the rest of your post, fascinating stuff. I'll do some reading up.
Cheers
John


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## DonL (Dec 27, 2012)

I disagree in general!

The Diesel propulsion system was groundbreaking.

After the decision to go with the high pressure steam turbines from Bremen Class (Bremen (1929)) at 1934, the research funds to MAN were massivly shortened (1934).

After the massive problems with the high pressure steam turbines in servive the research funds to MAN were massivly boosted (1938), with result of the VZ 12 32/44 (1940), 24 Zylinder V engine with 60ts and 12500 PSe normal poweroutput, *without* help engines, for exampple compare to the MZ9 42/58 of the the Panzerschiffe with 7.100 PSe and 90ts, plus 43ts MZ5 42/58 for the help engine for two MZ9 42/58 .
Three were built with turbo charging till 15000 PSe for normal poweroutput an example is at the Museum of Sinsheim.

The VZ 12 32/44, 24 Zylinder V engine was revolutionaire for the propulsion system of Warships, Cruisers and Destroyers, and I think it could be ready 1938/39 without the switch of to the high presuure steam turbines.

A BB with a 4 shaft propulsion system could manage to get 16 x 12500 PSe = 200000 PSe normal poweroutput to the water with Diesel engines and the massive pros of the consumption and without any disadvantages at the weight, because this engine weight only 60ts without any help engine.


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## Shortround6 (Dec 27, 2012)

The Diesel propulsion systems were hardly "ground breaking". First ocean going ship to use a diesel was in 1910 and first to use a diesel as the sole means of propulsion was in 1912. A diagram of a "diesel" engine room layout for a dreadnought can be found in the 1913 Brassey's annual (never actually built). 

If the information in Wiki is accurate the Bremmen didn't use high pressure steam by the standards of WW II. A bit above "normal" perhaps. Bremen used 23 Atm pressure. Hipper class used 85 Atm? British battleships of the 1890s use 14-15Atm.


The weights given for those WW II engines seem a bit optimistic, A current MAN brochure shows a modern 4 stroke turbo charged V-16 diesel of 12,182hp max continuous (a 32/44?) weighing 87 tons.

http://www.mandiesel.com.cn/files/news/filesof15981/32_44 CR.pdf



Granted the older engines may have been two stroke double acting but MAN uses the first number as an indicator of the bore in centimeters and the second as the length of the stroke. There is also a bit of confusion as to what maximum continuous may be. Ships run 1 hour, 4 hour and 8 hour trials, not 5 minutes like airplanes. But some engine makers rate engines for different duties. A electrical generator engine ( 24 hours a day for weeks on end) will be rated lower than the _same_ engine for even work boat duty let alone more intermittent use. 

I will note that a modern Diesel can operate at about 4 times the BMEP of a 1920s diesel however.


"In 1914 there were fewer than 300 diesel powered vessels in service with an aggregate tonnage of 235 000 grt; by 1924 there were the fleet had grown to some 2000 ships of almost two million grt and by 1940 the total tonnage had risen to 18 million grt embracing 8000 motor ships."

From "Pounder’s Marine Diesel Engines and Gas Turbines" 

available here: http://www.albadr.org/www/pdf/library/487.pdf 

The Germans suffered from trying to push the envelope a bit to far both with the Diesels and the high pressure steam. What works in test installations ashore doesn't always work so well in a sea going ship ( and what works in a ship often doesn't work in a railway locomotive).
A lot of early installations of _light weight_ machinery had to be de-rated in order to get the desired reliability. 

The degree of reliability (or unreliability) that can be tolerated in small high speed ships/craft built by the dozen (if a full destroyer flotilla has to leave one or two ship/s behind with bad engines it is not a disaster) is not what is wanted for big ships built in small numbers where a bad engine can seriously affect the battle fleets strength..


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## davebender (Dec 27, 2012)

> After the decision to go with the high pressure steam turbines from Bremen Class (Bremen (1929)) at 1934, the research funds to MAN were massivly shortened (1934).
> After the massive problems with the high pressure steam turbines in servive the research funds to MAN were massivly boosted


The KM and German merchant marine had a wealth of experience with diesel propulsion from 1910 onward. I don't understand why Admiral Raeder was so determined to use an unproven high pressure steam system.


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## Shortround6 (Dec 27, 2012)

Because, as we have been saying, the available diesels of the _time_ could not provide the needed (wanted) power at a low enough weight or volume. Neither could _normal_ pressure steam power plants.


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## delcyros (Dec 29, 2012)

> Because, as we have been saying, the available diesels of the time could not provide the needed (wanted) power at a low enough weight or volume. Neither could normal pressure steam power plants.



That´s incorrect. See above post of 4th of dec. Diesel was well capable to provide the power required to propel a fast battleship or a cruiser within the confines of the not-so-confined-german-machinery-spaces.
Correct is that HP plants -when new in 1933 to 1938- typically claimed more efficiency than it was cabale to deliver. The selling companies made it up. A higher fuel efficiency negated one of the principles of Diesel propulsion hence the Diesel was dropped after preliminary successes with the PBB´s. That´s not because the PBB´s were considered to be a failure. The Panzerschiff D ERSATZ ELSASS was to be buildt initially by MAN DIESEL engines, too. The change to HP turbine was a recognized failure in NÜRNBERG, HIPPER´s, SCHARNHORST´s, BISMARCK´s and GRAF ZEPPELIN´s (all laid down 1934 to 1938). It took time until lessons could be learnt from the newly laid down vessels. The H-class and ALL SUBSEQUENT classes of KM cruiser and BB´s were designed with Diesel propulsion instead. 



> Granted the older engines may have been two stroke double acting but MAN uses the first number as an indicator of the bore in centimeters and the second as the length of the stroke. There is also a bit of confusion as to what maximum continuous may be. Ships run 1 hour, 4 hour and 8 hour trials, not 5 minutes like airplanes. But some engine makers rate engines for different duties. A electrical generator engine ( 24 hours a day for weeks on end) will be rated lower than the same engine for even work boat duty let alone more intermittent use.


The specifications of the marine Diesel engines in question are well understood. Max. continuous rating can be found as "Höchstzulässige Dauerleistung" in the MAN specification for each marine engine. Rated power was typically only lightly higher and aviable for 10 hours and MAN Diesels were expected to have a 10% safety margin with short term power (1 hour for marine Diesel).


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## Shortround6 (Dec 29, 2012)

Technology can swing back and forth. A diesel that hits it's performance numbers in 1940 is just a big a gamble to a ship that started construction in 1939 as the high pressure steam plants were. If it fails there is an awful lot of rework to do. 

It is also difficult to get good numbers for some of these installations or to try to compare them from ship to ship, especially between classes. One book gives "entire" (whatever that means, including auxiliary power plant/generators but not fuel? propeller shafts and propellers?) "propulsion system" weights of Deutschland as 21.96kg per HP. and the Hipper at 18.5kg per HP. Same book says 20.3 KG per HP for the "entire drive installation" for the Bismarck and the "entire power installation" for the "H" class as 31.4 KG per HP. Notice the different wording? 

Germans had been "burned" several times during WW I by Diesel makers failing to deliver promised engines for German Dreadnoughts. 

Some of the later _planned_ German ships were to use mixed propulsion systems. The O,P,Q battle cruisers were to use cruising diesels of 60,000shp with a steam turbine of 116,000shp. The M class light cruisers of 1938 were to use diesels on the center shaft and steam turbines on the wing shafts as did the SP 1-3 scout cruisers. The Germans schemed an all diesel destroyer in 1938 but actual construction of Diesel destroyer wasn't started until 1943, it was never completed due to bomb damage while building. 

My comments about what is meant by "maximum continuous power" is while we may know what MAN means in a 2007-2013 brochure it may not be what was meant in in 1940-41. The Modern MAN diesels at the modern "maximum continuous power" rating do _NOT_ match for a power to weight ratio what is claimed for the 1940 engines. Perhaps a different definition of MAX CON power is the explanation or perhaps the 1940 engines did not have the power to weight claimed?


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## fastmongrel (Jan 4, 2013)

Apropos of nothing but just to show steam tech still has plenty to show for itself. A few years back I worked as a contractor for a firm installing a steam generating plant in an edible oil refinery. The obsolete 1960s steam plant we removed was the size of a 40 ft shipping container with a feedwater condenser of about half the size. They were connected by a snakes honeymoon of pipework and all this was controlled by a switch panel worthy of a 1950s computer all flashing lights, dials and valve levers, all contained in a seperate boiler house. This was cut up by yours truly with a gas axe and taken away by a scrap merchant in quite a number of lorries. 

The replacement steam generator came on the back of a medium sized lorry and was put onto its concrete base by a fork lift. It was roughly the size shape and look of a large double door catering refrigerator with a discrete control panel. When we hooked it up to the fuel and water supply and all the pipework which fed the steam to the refinery we pressed a button stood back and within 10 minutes steam was blowing out of all the relief valves in the refinery. The refinery man who had run the old plant for about 30 years said it took the old boiler the best part of a shift to build pressure up.


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## Glider (Jan 6, 2013)

Readie said:


> Shortround, We'll have to agree to differ about Mallard's tech spec being 'low tech', she was the first A4 to be fitted with a Kylchap double blast pipe and her WSR, which is held to this day, speaks for itself.
> The steam gunboats were turbines not compound pistons. Great performers in heavy seas but, having to be kept 'in steam' was a disadvantage.
> The British Gun Boats etc with 4 × Packard 4M 2500 petrol engines, total 5,000 hp went well but, the thought of sitting on all the petrol is eye watering....
> A pretty explosive choice really....superheated steam or petrol.
> ...



The Steam Gunboats had armour added to the boilers to at least make them bullet/splinter proof which slowed them down a bit. Still an explosive choice I agree


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