The Propulsion of SMS Prinzregent Luitpold

The following was posted on MARHST-L in November 1999, and is reproduced here by permission of the author.

From Maxwell Mulholland (BlauerMax@AOL.COM)

Please let me apologize for the re-opening of this discussion thread, but two books which shed light on the issue that I had loaned a friend several months ago were just returned to me this week. I read the earlier postings on this topic with great attention and thought that the quality of the contributions were excellent. What I found in my reference works should be of interest to those who followed the subject matter.

The background of PRINZREGENT LUITPOLD's propulsion set is discussed in great detail on pages 102-106 of Axel Griessmer's definitive book "Linienschiffe der Kaiserlichen Marine 1906-1918" ("Battleships of the Imperial Navy 1906-1918", Bernard & Graefe Verlag, 1999). I will summarize the main points:

The decision to replace a turbine set in a battleship with a propulsion diesel was made in December 1910. The impetus to this resolution had been a spontaneous decision by Admiral von Tirpitz on January 15th, 1910, to equip a capital ship with an "oil" (i.e. liquid fuel) main engine. Many senior officers were aghast at this proposal, as the new turbines on board Germany's battleships had at this point still not been extensively tested. The thought of placing two new propulsion technologies on board a major warship was considered by conservative officers to be gangerously irrational.

Tirpitz's line of reasoning was based on an influential study submitted to him in December 1909 by the Konstrukteurdepartement of the Reichsmarineamt (RMA). This study was titled "Denkschrift betreffend Verwendung von Verbrennungsmotoren zum Linienschiffsantrieb" ("Memorandum on the Use of Internal Combustion Engines for Capital Ship Propulsion"). The basic findings of this document were that significant savings in both space and weight could be obtained by substituting IC engines in place of steam propulsion plants.

For a given weight of fuel it was thought that a ship with IC engines would have 3-4 times the range of a ship with boilers and either turbines or triple-expansion engines. The engine-building firm MAN even guaranteed a fuel useage rate of 0.2kg/SHP -- one quarter that of coal/steam plants. In addition, it was noted that the lack of boilers would greatly cut down on the huge number of engineroom personnel needed to man the big ships, and the cleaner engine exhaust gases would be much less visible to an enemy observer than the masses of dark stack smoke produced by coal burners. Also, re-fueling would be much faster and simpler and would eliminate the periodic coaling exercise hated by crews. Lastly, the RMA calculated that IC main engines would cost approx. RM140/SHP -- about RM30/SHP cheaper than the turbine sets then being procured for the Imperial Navy...therefore potentially lowering the price of a 28,000SHP battleship by RM840,000!

According to Griessmer, another reason for Tirpitz to follow this course was to turn the technological tables on the Royal Navy, which had surprised the Imperial Navy through its rapid large-scale adoption of marine turbines. Tirpitz thought that Germany's substantial lead in the design and development of large diesel engines would lead to a strategic advantage that the British could not easily duplicate (Tirpitz was adamant on this issue, and made many enemies in industry when he forcefully prevented MAN from licensing its diesel engine technology to Vickers in what would have been a very lucrative deal).

The RMA signed a contract with MAN on February 13th, 1910, to develop a diesel engine that could propel a capital ship. Initially this was to be a 3-cylinder 6,000HP demonstration model, to be followed (following successful testing) by a 6-cylinder 12,000HP prototype. Although the initial engine was completed in the spring of 1911, serious technical problems plagued the development project and caused a "series of disappointments". It was not until April 1917 that the large engine successfully passed its tests and was declared ready for shipboard use. On pages 114-115 of Gerhard Koop's book "Von der NASSAU- zur KOENIG-Klasse" ("From the NASSAU- to the KOENIG-Class", Bernard & Graefe, 1999) there are pictures of PRINZREGENT LUITPOLD's massive engines under construction.

The long delays meant, as we all know, that P-L went to sea with her central engineroom unused and her middle shaft alley empty and welded shut. The advanced plans to equip the follow-on KOENIG class with central diesel propulsion engines were scrapped, and construction contracts were re-written to add a third turbine set instead. P-L's performance rivalled that of her sisters...her 14 boilers and twin Parsons turbines produced a remarkable 38,751SHP that drove her at 21.7 knots (one explanation for her speed is that she carried two three-bladed 4 meter-diameter propellers, while her sisters only carried 3.75 meter-diameter screws).

[and a follow-up posting:]

My interpretation of this issue is that Admiral von Tirpitz' embrace of diesel propulsion for battleships was primarily driven by a financial (as opposed to a tactical or operational) impetus. The spiraling cost of capital ships was putting inexorable pressures on Tirpitz in his increasingly difficult dealings with the appropriations committee of the Reichstag. The advertized economic benefits of diesel engines in regards to their superior (lower) acquisition cost and operating costs vis a vis the traditional boiler/turbine system seemed paramount in his calculations to pursue this direction. While one can laud Tirpitz for his visionary initiative in ordering the development of large diesel engines for capital ship propulsion, in hindsight this seems primarily to have been a cost savings measure.

On the other hand, the internal RMA opposition to diesels was not simply the reactionary response of a conservative clique of closed-thinking admirals. Many leading German naval architects did not agree that over-sized internal combustion engines were yet a mature enough technology upon which to drive large warships. They were skeptical of the claims of their more enthusiastic colleagues in regards to potential space and weight savings to be derived.

These opponents pointed out that the large diesels on the drawing boards of MAN were so tall that they would penetrate through the standard armored deck arrangement being designed into all Imperial German Navy battleships of the day. In addition, the wholesale elimination of coal bunkers in the future meant that the entire battleship underwater protection scheme would have to be completely re-thought. This faction claimed that this meant that *additional* armor -- both horizontal as well as below the water line -- might in fact have to be added to ships, thus obviating the proclaimed weight savings.

Last Updated: 21 November, 1999.

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