Naval History Forums

Do not know if this has already been asked and answered already so here goes.
I seen the statement on a number of occasions where the large size of the engine spaces was because the Bismarck's design was initially due to the idea of an electric drive plant was going to be used. Suggestions that either diesel electric or turbo( steam ) electric. Ok , now I also seen it stated that a ship is designed around the chosen engine type initially, which suggests that either a actual design was on the cards or had been designed. Very little information on actual power unit is listed which is interesting given how much the Bismarck's design was apparently based on it. Can anyone fill in the missing details for me?

If I recall the favored design had been with turbo electric propulsion, but the decision was made to keep to a type displacement of 41,000 tons by Raeder in January 1936. However, the turbo electric propulsion system was considerably heavier than regular geared turbines and would have required a reduction in either armour or armament in order to keep to the tonnage figure. Subsequently Raeder approved the adoption of geared turbines and this allowed for a weight savings that was applied to improved armour protection. The change, authorized in June of 1936 however, required a complete redesign of the power plant installation, so it was not a matter of simply fitting the turbines into the previously allocated spaces for the turbo electric drives.

That the turbine room spaces were larger was mainly due to the size of the turbines themselves and their associated sea chests and condensors. A four shaft arrangement would have allowed for four smaller turbines to achieve the same horsepower as the larger three that were adopted, but would have complicated watertight subdivision, particularly in the long shaft runs where they exited the through the torpedo defence system.

The question I have is I had read that there is or was a belief that the design of any warship is in part based on her choice of engine and swapping engine design after what seems be a firm design, is not a easy change to implement.
The fact that the design had been finalized at least the engine spaces size requirements, a actual engine plant would have at least theoretical specified. There has seemly been no mention of design firms, size and type of motors etc.
The two states of affairs do not seem to match up each other. Can any one at least hazard a guess which company was to design this 'turbo electric' plant, what it would have weighed etc.

If memory serves, Siemens was involved in the turbo electric drive. BS machinery was built by Blomand Voss. Tirpitz was equipped with machinery from BBC

Thank you something to start with, although there seems to be a lack of detail in company websites of historical designs from that period from German companies, I will see if anything comes up.

Whit this being discussed, does anyone know if there are drawings of the Bismarck's engine's? As a mechanical designer I always love to pour over piping and equipment arrangements. Any info appreciated!

I believe they were licensed copies of Parsons and Curtis wheel turbines. What would be interesting is the reported automatic settings control systems. Instead of having someone controlling manual controls, it is reported that the controlling was via a automated system.

To answer my original question the turbo-electric plant never got past the initial thought stage. I believe the chosen design company refused to guarantee the performance of the proposed system given the time frame for development of the final product. That suggests that there was some urgency to the development that was not to normal practices.

One reason for the large size and weight of Bismarck's machinery spaces is that she had 12 boilers, each of which could produce steam for about 13000shp. By way of comparison KGV had 8 boilers, each of which could produce steam for about 17000shp. KM large ship machinery was hampered by reliance on relatively small, numerous boilers. An extreme example of KM machinery inefficiency is in the Hipper class cruisers, which also required 12 boilers, each of which could only produce enough steam for 11000shp versus 4 boilers in the Belfast class, each producing steam for 20,000shp.

One reason for the large size and weight of Bismarck's machinery spaces is that she had 12 boilers,

what was the complete weight of KGVs machinery (Turbines, boilers, shafts,screws, fuel piping,pumps, supercharger and so on, (but without any liquids))
Bismarcks complete weight(M I) was 2803 metric tons

do you have individual weights for the british boilers?

I believe the more accurate reasoning for the size of the boilers lies in their original designed purpose. It has been suggested that the orginal units were designed to fit in destoryers and the units used in the BS were beefed up versions. For their size their heat transfer rating is MORE efficient as they produced higher steam pressure for a smaller heating surface in a shorter time from cold start up than the British units. Having 12 units instead of 8 is NOT a negative either when you consider 'battle redundancy' as you have 4 boilers servicing each turbine set, as opposed to 2 per set in the British units. I think if you would look a bit deeper into the engine casualties suffered by the German units you will find it is MORE to do with fuel contamination than poor so called inefficient designs.

Thorsten Wahl wrote:

One reason for the large size and weight of Bismarck's machinery spaces is that she had 12 boilers,

what was the complete weight of KGVs machinery (Turbines, boilers, shafts,screws, fuel piping,pumps, supercharger and so on, (but without any liquids))
Bismarcks complete weight(M I) was 2803 metric tons

do you have individual weights for the british boilers?

Bismarck has a 3 shaft layout, so direct comparisons of overall weight between KGV and Bismarck PPs are not valid. I do have some weight figures for KGV class boilers, but it will be a day or so before I can get to them.

The first estimate for the main machinery (turbo-electric) on August 30th 1935 was 3000 mt. It rose step by step to 3525 mt in May 1936. All drafts had the same upper limit of 42,000 long tons. The last draft exceeded this limit by 142 mt. The first estimate for geared turbines on June 3rd 1936 was 2300 mt with a weight reserve of 933 mt for the whole ship. About 500 mt of the saved weight were again used for the main machinery, 206 mt were used for the main armor belt (300mm to 320mm) and 156 tons were used for changes of the hull. The rest was used for minor changes. That’s why the weight of the main machinery rose to 2800 mt in December 1st the same year with only 42 mt reserve left for the whole ship. On March 30th 1940 the weight of the main machinery was calculated with 3335 mt.

The main reason to use the geared turbine instead of the the turbo-electric machinery was that they realized there were at least three problems they couldn’t solve with a displacement of 42,000 tons:

-Reversing the rotation of the propellers at top speed was infeasible, because the torque was too high.
-Putting the helm increased the torque on the inner propeller too much. Turning trials at top speed wouldn’t have been possible.
-At cruising speed all propellers would have had the same revolution (but different rotation directions would have been possible).

Some clarification please about problems listed

1./ Is there not some sort of braking method used in either system? I think in either case there would have to be a transition stage as you could not just apply full reverse power and expect the everything to instantly be going in the other direction. The Yanks did not seem to have an issue with it.

2./ What structural changes would have resulted in the inner shaft and prop to have been affected by rudder changes? Three shaft arrangement was never going to change.

3./ In either case the three shafts rotated or would have rotated at the same revolutions any case. Any harmonic vibrations or vibrations from interference from the other propellers is simply avoided by not setting the power output at a level that created them in the first place. I believe that is the standard operational method.

If avoidance was required by alteration to the design instead the usual practice is change propeller design between shafts.

And how does any these issues relate to overall displacement other than the general weight differences of the plant types in question.

I will again state the most mentioned reason for the lack of any turbo electric plant seems to have been a disagreement between the amount of time required for development of the design between the desired manufacture and the navy high command.

I as yet to find a more plausible suggestion.

dunmunro wrote:

Thorsten Wahl wrote:

One reason for the large size and weight of Bismarck's machinery spaces is that she had 12 boilers,

what was the complete weight of KGVs machinery (Turbines, boilers, shafts,screws, fuel piping,pumps, supercharger and so on, (but without any liquids))
Bismarcks complete weight(M I) was 2803 metric tons

do you have individual weights for the british boilers?

Bismarck has a 3 shaft layout, so direct comparisons of overall weight between KGV and Bismarck PPs are not valid. I do have some weight figures for KGV class boilers, but it will be a day or so before I can get to them.

Total dry weight for KGV's machinery was 2770 tons but, of course, she had 4 shafts but we can see how the reduced number of boilers offsets the use of 4 shafts.

The weight of a KGV class boiler was 52 tons (G&D) versus 52.8 tonnes wet, and 48 tonnes, dry, in Bismarck (from Koop). I suspect that the KGV weights are dry but they still show a better power to weight ratio.

some other weights:
Valiant (1939) wet = 140000lb = 62.5tons = 10,000shp/boiler
Hipper wet = 62.8 tonnes = 11000/shp/boiler
RN War emergency DD wet = 75.9 tons =20000/shp/boiler

I thinkyou are reading too much into a probable 800kg weight difference. As far as a measure of efficiency of a boiler is measured, a boiler of small size that physical weighs the same as a supposed larger type suggest more internal heating surface for a given area. Therefore a boiler that is smaller, produces higher water temperatures and pressure is usually considered more efficient than a larger boiler producing lower pressure and temperature.

The efficiency of a boiler can not be directly measured in shp produced by the turbines attached to it. Shp is a direct measure of turbine efficiency not boiler efficiency so the correct argument would be to question overall turbine efficiency instead. Normally higher pressure and temperatures of the feed water, or more correctly the super heated steam that is produced by the heating of the feed water, equates to higher turbine efficiency, so what happened in this case is interesting.