Mauretania's machinery

The Mauretania, built by Swan Hunter of Newcastle, and her sister ship Lusitania, built by John Brown of Clydebank, were the biggest, fastest liners in the world when they went into service in 1907. The Lusitania’s fate at the hands of a U-Boat is well-known.

The owners, Cunard, showed great confidence in the fairly new fangled technology by opting for turbine propulsion on a big scale.

The turbine rotors comprised a forged shaft on which cast steel wheels were shrunk. Then, shrunk onto the wheels, was a cylinder (the drum or barrel), which was machined to receive thousands of blades.

I’d previously posted a description of how hollow turbine rotor barrels or drums were being made by expanding a hollow forging using squeeze rollers in 1903. For some reason, Lusitania’s rotor drums were forged at John Brown’s in Sheffield in the ‘traditional’ way using a hydraulic press and a mandrel. Quite a feat, at nearly 12 feet diameter and only about 3” thick.

Mauretania’s LP rotor drums must have been even more of a challenge. They were forged with integral flanges and ribs inside the drum. Each finished drum was actually assembled from three separate barrels approx 12 feet diameter and 2 inches thick (about 6 inches thick at the internal ribs and flanges). The three sections were SCREWED together, after heating the female section to give a shrink fit. Buttress threads were adopted. If threads with tapered contact faces had been used, this would have caused unwanted stresses to build up as the hot ‘female’ drum contracted. Finally the internal flanges were bolted together.

Mauretania’s rotor forgings were produced by Armstrong-Whitworth in Manchester using ‘Whitworth’s fluid pressured steel’ (the molten metal in the ingot mould being subjected to enormous hydrostatic pressure with the aim of improving homogenity). By the way, that’s Whitworth as in Joseph Whitworth and Armstrong as in William ‘Hydraulic’ Armstrong (as in Armstrong, Mitchell - cranemakers, shipbuilders, etc of Newcastle).



The photo shows one of Mauretania’s LP rotors in at Wallsend Slipway & Engineering, Newcastle-on-Tyne. Note the size of the operators. Just to confuse matters, the lathe was made by Armstrong-Whitworth in Manchester. Incidentally, the town of Wallsend got its name from the fact that it was the Eastern end of the Roman Hadrian’s Wall.

The finished LP rotors weighed 125 tons. Each LP rotor had no less than 50,000 blades. These were fitted in only two weeks, helped by the fact that as far as possible they were pre-assembled in groups before fitting to the rotor.

The following link shows a collection of toffs being taken past some of the turbine casings, borne in cars to minimise the chance of coming into contact with any of the working class heroes.....

Casings

To be fair, the visitors had a lot to see, as they were also taken to the shipyard and driven through some of the recumbent funnels......

http://www.amber-online.com/gallery/exhibition39/image39-628.html

The cast iron turbine casings were marvels of foundry work. Not only were the casings extensively ribbed, the ribs themselves had flanges (i.e. the ribs were T-shaped in cross section). Plenty of overtime in the core shop, then.

Another foundry feat was the casting of the shapely steel stern frames, by the Darlington Forge Co.:-

WOW

Asquith,

Great stuff (er, gubbins?). Keep 'em coming.

Can't quite tell if the shaft struts were cast as part of the stern frame? Looks like they were.

Jeff Greenblatt

I like these kind of posts. Keep'em coming.

Thanks for the comments.

Geoff,
The casting is all in one piece. This made life very difficult, because of the great variation in section thickness. The thin sections solidified and cooled relatively quickly compared with the more massive sections. Also, being steel, the contraction was much greater than with cast iron. This caused a tendency for the solidified thin sections to tear (especially as the metal was hot and therefore weak). Soon after casting, much hot toil was needed in order to collapse the mould in the area of the thin sections. This ensured that thethin parts could contract without being constrained by the mould.

The picture below shows a larger stern frame, but this is actually in two pieces. It's not evident from the photo, but there's a vertical flange on the other side. The man is holding it up while it’s getting the attention of a horizontal borer at Darlington Forge. The hole for the middle propeller shaft is being bored. This stern frame still exists, but is not readily accessible. It’s on the sea bed, being part of the Titanic.



Incidentally, the reason why the Lusitania’s turbine rotor drums weren’t rolled using John Brown’s high tech squidging rolls can be explained by a mistake on my part: they came into use c.1908, not 1903.

De-goddamn-lightful!

(please note the use of one of only a few "infixes" in our language)

Asquith:

I assume that those are prop-speed turbines. The gear drives would follow closely thereafter.

I have a very old book on steam turbine propulsion published the the US Naval Academy in Annapolis. Because of the high speed requirement, war ships had to have two sets of turbines. The main turbines and a set of cruise turbines for running with the fleet. The machinery layout was horrendous!

By the way, the set up gives rise to the Star Trek terms "Impulse Power" (cruise) and "Warp Drive" (high speed running)

Thank you Asquith. I never cease to be impressed with the skill of the men who built those ships. Wonderful foundry work.

Is this sort of work being done anywhere in the world today, or is it all done with weldments?

DryCreek,

I was surprised to learn that stern brackets are still cast:-
http://www.sheffieldforgemasters.com/cast_defence.php


Jim,

Yes, the turbines were direct-coupled to the props.
I was surprised to find that Parsons was pursuing the goal of higher turbine speeds and slower propeller speeds at an early date, and had a small vessel with double helical gearing in service as early as 1897. A full-sized geared turbine cargo ship, the SS Vespasian, was operating in 1908. More info here:-

http://www.history.rochester.edu/steam/parsons/part3.html

High speed , high power gears evidently held less fear for Parsons than they did for Dr Fottinger, who developed a system with a high speed turbine driving a centrifugal pump, and using this to drive a water turbine which in turn drove the propeller.

Turbo electric ships were also in service early in the 1900s.

Replacing Vespasian’s reciprocating engine with geared turbines gave a 17% reduction in fuel consumption at the same speed.

Gearing was initially introduced to allow turbines to be used in relatively merchant ships. Previously only fast vessels - liners and warships – had turbines.

The first high-power application of naval geared turbines was for 22,500 HP destroyers in 1912. I doubt that the engine room crew regretted the demise of large high speed recip engines.

Geared turbines became universal for new medium and large Royal Navy ships in WW1. This was because of increased efficiency resulting from higher turbine speeds and lower prop speeds. Further improvement soon came with double rather than single reduction gearing.

By the way these were Parson turbine meaning direct drive. No reduction gear. Inefficient as these were the cost/benefit of engine inefficiency Vs overhaul and maintenence gave the advantage to turbines over multi stage recip engine. The first cost advantage went to recip engine. Scalable HP when to turbines. Recip steam engines seem to poop out at 10,000 SHP. Ship steam turbines range up to 80,000 SHP. 90,000 gas turbine engines are offered for fossil fuel ships. Diesels up to 120,000 SHP for container and bulk crude are propoade for the next generation.

Coal plant steam turbines run up to 300,000 HP at my last info. Hydo-electric trubine up to 1M HP.

I suppose if GHP will be required some day some one will step forward with a perfectly sensible design.

Parsons’ contribution to the modern world went well beyond the development of large turbines. His far-sighted activities included astronomical telescopes. Grubb-Parsons stayed in the business for many years, and I saw one of their mirror grinding machines when I visited Parsons’ works in the 1990s. Probably the one in the first photo here:-

http://www.star.ucl.ac.uk/~sk/osl/omt/omt.html

Parsons also played a key role in the development of high speed/high power gears, developing the ‘creep method’ of hobbing gears.

However, credit for the first adoption of high speed double helical gears for (small) turbines goes to de Laval of Sweden. Also in Sweden, the Ljungstrom Brothers introduced an oddball helical gear, with helixes at two angles, described in this post about steam turbine locomotives:-

http://www.practicalmachinist.com/ubb/ultimatebb.php/topic/11/2056.html