3-shaft propulsion

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marcelo_malara
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Re: Battleship Bismarck: A Design and Operational History

Post by marcelo_malara » Thu Aug 01, 2019 3:15 am

So it would be lighter than KGV´s?

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Re: Battleship Bismarck: A Design and Operational History

Post by Byron Angel » Thu Aug 01, 2019 3:59 am

Sometime things can depend upon what is counted as part of machinery weight and what is not. Different navies might have different protocols.

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Re: Battleship Bismarck: A Design and Operational History

Post by dunmunro » Thu Aug 01, 2019 5:08 am

marcelo_malara wrote:
Thu Aug 01, 2019 3:15 am
So it would be lighter than KGV´s?

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Yes, and it directly compares the weight of a 3-shaft versus a 4 shaft powerplant with the same output.

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Re: Battleship Bismarck: A Design and Operational History

Post by marcelo_malara » Thu Aug 01, 2019 6:33 pm

dunmunro wrote:
Thu Aug 01, 2019 2:28 am
marcelo_malara wrote:
Tue Jul 30, 2019 4:55 am
There are three items in the destroyer´s weights labeled machinery/auxiliary machinery in Whitley´s book, don´t know exactly what is each. For a proper comparison I would turn to battleship´s machinery.

According to Burt KGV´s machinery weighted 2700 t, for 110.000 hp at 400 psi (27 kg/cm2).

Garzke gives 2863 t for Scharnhorst (125000 hp at 52 kg/cm2) and 2756 t for Bismarck (135000 hp at 58 kg/cm2).

KGV: 40 hp/1 t of machinery

Sch: 43 hp/1 t of machinery

Bs: 48 hp/1 t of machinery


So, almost doubling the steam pressure gives between 10/20% of machinery weight saving.
Per Friedman, the Illustrious class carriers had 3 shaft machinery that had ~110k SHP output and weighed ~2450 tons.
So the RN got a 250 t saving going from 4 to three shafts, that make sense. We can also say that the 10% lighter German machinery came from a reduction of shafts. I can no longer see the benefits of the high pressure of German design.

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Re: Battleship Bismarck: A Design and Operational History

Post by pasoleati » Thu Aug 01, 2019 10:10 pm

Folks, the Richelieu's machinery gave 155,000 shp on 4 shafts and the machinery weighed 2875 tons (=53 shp/ton). Steam conditions were 27 kg/cm2 and 350 deg C.

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Re: Battleship Bismarck: A Design and Operational History

Post by marcelo_malara » Fri Aug 02, 2019 1:16 am

pasoleati wrote:
Thu Aug 01, 2019 10:10 pm
Folks, the Richelieu's machinery gave 155,000 shp on 4 shafts and the machinery weighed 2875 tons (=53 shp/ton). Steam conditions were 27 kg/cm2 and 350 deg C.
This is getting good! I made some rough calculations of machinery and boiler room volumes from Bismarck (from Brower´s) and Richelieu (from Duma´s). The results are:

-Bismarck: 10044 m3
-Richelieu: 8363 m3

I have those spaces lenght and helght of KGV (from Burt´s), if anyone has the widths we can add to the comparision.

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Re: Battleship Bismarck: A Design and Operational History

Post by Byron Angel » Fri Aug 02, 2019 1:27 am

marcelo_malara wrote:
Thu Aug 01, 2019 6:33 pm
So the RN got a 250 t saving going from 4 to three shafts, that make sense. We can also say that the 10% lighter German machinery came from a reduction of shafts. I can no longer see the benefits of the high pressure of German design.
I do recommend that you consider reading the book I referenced in an earlier post - it is a relatively short read, easily accessible by the layperson (I know because I am one such individual) and provides an excellent description of the decisive factors which led the USN to migrate from WW1-era direct drive/single reduction turbine and low temperature/low pressure boiler technology to modern lightweight double-reduction turbines and high pressure/high temperature superheat boiler systems. The author was the Chief of the USN Bureau of Engineering during the period in which this all evolved and became the established standard.

The short story -
> The new high-speed lightweight turbines with double-reduction gearing were far more reliable and still delivered efficient prop rpm.
> The new high pressure/high temperature superheat boilers delivered much superior thermal efficiency, which resulted in deamatic fuel economy advantages.
> Such an engineering plant was typically lighter than the older standard designs (for example - the weight saving realized in US DD designs of the late 30's was equivalent to the weight of the ship's entire main battery + ammunition).
> The new engineering plant, in the same class of ship, would delivered a higher maximum speed.

Note 1 - The RN had undertaken boiler research along similar lines in the years immediately after the end of WW1, but the program fell victim to budget cuts. IIRC, DK Brown wrote on this topic.

Note 2 - My understanding of German marine engineering circa WW2 was that, like most German technology, it was on the cutting edge, highly efficient when it was working correctly, but very finicky in operation and liable to breakdowns from time to time (see the earlier experience of the Imperial German Navy with turbines in WW1).


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Re: Battleship Bismarck: A Design and Operational History

Post by marcelo_malara » Fri Aug 02, 2019 4:08 am

Thanks, I will give a look to that book.

Anyway, consumption numbers do not look good either. According to a table on Koop´s, page 28 of the English edition, Bismarck at 138000 hp, 265 rpm, attained 29 knots with a consumption of 325 g/hp/hr, that would be 44.85 metric t per hour. USS Massachusetts, in an article in WI I have already mentioned, says that "sustained fuel usage for 24 hours was 935.75 t at full power". Full power was 130000 hp at 185 rpm and 27 knots. If the 935.75 t were US tons, they would be 35.36 metric t per hourl, 272 g/hp/hr. If they were imperial tons, they would be 39.65 metric t per hour, 305 g/hp/hr. In any case, the higher pressure does not bring better consumption.

Two more comments. Massachusetts had double gearing. Most BB had a shaft speed of around 180 rpm at max power. Don´t know why the Germans went to 270 rpm for max power.

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Re: Battleship Bismarck: A Design and Operational History

Post by pasoleati » Fri Aug 02, 2019 6:14 am

Aa far as I know, the USN was the only one to adopt double-reduction gearing in their steam plants in large scale by WW2.

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3-shaft propulsion

Post by pgollin » Fri Aug 02, 2019 9:58 am

The RN looked at double reduction gearing and wasn't impressed - at that time the efficiency savings weren't great and the costs and maintenance increase weren't thought to be worth it. Post-war reports basically stated the same with the big regret being lack of reliable high pressure boilers.

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Re: Machinery Volume

Post by José M. Rico » Fri Aug 02, 2019 12:06 pm

marcelo_malara wrote:
Fri Aug 02, 2019 1:16 am
I made some rough calculations of machinery and boiler room volumes from Bismarck (from Brower´s) and Richelieu (from Duma´s). The results are:

-Bismarck: 10044 m3
-Richelieu: 8363 m3

I have those spaces lenght and helght of KGV (from Burt´s), if anyone has the widths we can add to the comparision.
Marcelo,
For Bismarck the volume of the 6 boiler rooms + 3 turbine rooms is 10,250 m3 (9,835 m3 without the cable alley).
The turbine rooms alone are 4,660 m3 (4,520 m3 without the cable alley).

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Re: Machinery Volume

Post by Herr Nilsson » Fri Aug 02, 2019 12:45 pm

José M. Rico wrote:
Fri Aug 02, 2019 12:06 pm
For Bismarck the volume of the 6 boiler rooms + 3 turbine rooms is 10,250 m3 (9,835 m3 without the cable alley).
The turbine rooms alone are 4,660 m3 (4,520 m3 without the cable alley).
boiler rooms + turbine rooms: 11,003 m^3
turbine rooms: 4,517 m^3
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Marc

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Re: Machinery Volume

Post by José M. Rico » Fri Aug 02, 2019 1:41 pm

Herr Nilsson wrote:
Fri Aug 02, 2019 12:45 pm
José M. Rico wrote:
Fri Aug 02, 2019 12:06 pm
For Bismarck the volume of the 6 boiler rooms + 3 turbine rooms is 10,250 m3 (9,835 m3 without the cable alley).
The turbine rooms alone are 4,660 m3 (4,520 m3 without the cable alley).
boiler rooms + turbine rooms: 11,003 m^3
turbine rooms: 4,517 m^3
Marc, I calculated the max. enclosed volume:

Center Turbine Room: 14 m (length) x 13.5 m (width) x 8.6 m (height) = 1,625,4 m3
Port/Starboard Rooms: 14 x 12.6 x 8.6 = 1,517,04 x 2 = 3,034.08 m3
3 Turbine rooms = 4,659.48 m3

Center Boiler Rooms: 13.9 x 9.6 x 8.6 = 1,147.584 x 2 = 2,295.168 m3
Port/Starboard Rooms: 13.9 x 7.8 x 8.6 = 932.412 x 4 = 3,729.648 m3
6 Boiler rooms: 6,024.816 m3

Boiler + Turbine rooms = 10,684.296 m3 (including cable alley)

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Re: 3-shaft propulsion

Post by marcelo_malara » Fri Aug 02, 2019 7:47 pm

Anyway we are within 10%.

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Re: Machinery Volume

Post by Herr Nilsson » Fri Aug 02, 2019 8:32 pm

José M. Rico wrote:
Fri Aug 02, 2019 1:41 pm
Herr Nilsson wrote:
Fri Aug 02, 2019 12:45 pm
José M. Rico wrote:
Fri Aug 02, 2019 12:06 pm
For Bismarck the volume of the 6 boiler rooms + 3 turbine rooms is 10,250 m3 (9,835 m3 without the cable alley).
The turbine rooms alone are 4,660 m3 (4,520 m3 without the cable alley).
boiler rooms + turbine rooms: 11,003 m^3
turbine rooms: 4,517 m^3
Marc, I calculated the max. enclosed volume:

Center Turbine Room: 14 m (length) x 13.5 m (width) x 8.6 m (height) = 1,625,4 m3
Port/Starboard Rooms: 14 x 12.6 x 8.6 = 1,517,04 x 2 = 3,034.08 m3
3 Turbine rooms = 4,659.48 m3

Center Boiler Rooms: 13.9 x 9.6 x 8.6 = 1,147.584 x 2 = 2,295.168 m3
Port/Starboard Rooms: 13.9 x 7.8 x 8.6 = 932.412 x 4 = 3,729.648 m3
6 Boiler rooms: 6,024.816 m3

Boiler + Turbine rooms = 10,684.296 m3 (including cable alley)
Jose,

I just took the values from a damage control list.
Regards

Marc

"Thank God we blow up and sink more easily." (unknown officer from HMS Norfolk)

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