More machinery weights

In D.K. Brown's book, The Grand Fleet, he provides a little more data about machinery weights. He says that a typical 1912 British cruiser design might have had machinery weighing 1050 tons and producing 30,000 SHP. That is about 28.6 SHP/ton of machinery. For the 1912 Arethusa class they wanted 40,000 SHP from a plant weighing 850 tons. That is 47 SHP/ton of machinery. In Brown's book Warrior to Dreadnought, there are a few other nuggets:

• destroyer Arab: 41.3 IHP/ton of machinery (1896)
• destroyer Express: 44.5 IHP/ton of machinery (1896)
• destroyer Albatross: 39.5 IHP/ton of machinery (1896)
• large cruiser reciprocating 41,000 IHP plant: 11 IHP/ton of machinery (1905)
• large cruiser turbine 41,000 SHP plant: 13.7 SHP/ton of machinery (1905)
• flotilla leader Swift: 32.7 SHP/ton of machinery (1905)

The lack of better weight data for British ships from 1890 to 1921 is particularly bothersome.

There is much better data for USN ships. For example, the Omaha class cruisers had a plant that produced 52.3 SHP/ton of machinery, and this was in a plant designed circa 1918. The Lexington class battlecruisers were designed with a plant that produced something like 31.4 SHP/ton of machinery. This was a 1919 design.