Engine Specifications as per the "engineering notebook"

[A. Gabriel]

Greetings to all fellow enthusiasts of the RMS Titanic. I am a newcomer from the Philippines intrigued by the particulars surrounding this magnificent ship, specifically the numbers behind it. Specifications, blueprints, mechanisms, all the minutiae, these fascinate me (among other reasons, because I desire to craft a model of the ship when I have the means and the time).

Coming across the esteemed article by Mark Chirnside, I was immediately taken by the wealth of information suddenly available for not just the propellers of Titanic and Olympic, but their engine specs as well. Copied below are the numbers for the Olympic-class liners, lifted directly from the "engineering notebook" of said article.

Propellers (for 401)
wing propellers: 23'6" diameter, 35' pitch, 120 sq.ft total area, 3 blades
center propeller: 17'0" diameter, 14'6" pitch, 120 sq.ft total area, 3 blades

Engine Details
"stm. pipe": 20 1/2 "
piston rod: 14", LP cylinder 11 3/4 "
piston rod screw: 11", LP cylinder 9 1/4 "
????? pin: 16 1/2 ", LP cylinder 13 1/2 "
"crnk. pin": 27 3/4 "
crank shaft: 27"
guide(?) shoe: 4'-0 3/4" x 3'-9", LP cylinder 3'-7" x 2'10"
reversing gear style: Brown

Assistance in deciphering the unclear headings in the original, as well as the terminology/meaning of said headings (I am not an engineer) is appreciated.

 

[Mike Spooner]

Hi A.Gabriel,
If you want a good basic book on Titanic speciation I recommend a book. RMS TITANIC Owners Workshop Manual by Richard de Kerbrech and David Hutchings.
Cylinders dia. LP 97in x two.: IP 84in :HP 54in. Stroke 75in.
Cheers.

 

[A. Gabriel]

Cheers, Mr. Spooner. Lamentably being in the Philippines renders me fairly impeded in the ways of procuring said book til I find myself employment — though from the preview pages I have found online, there is even information there concerning the Parsons turbine of the Britannic, an excellent find indeed.

Edit: something perplexing, that book says that there were 6 stages of expansion in the Parsons turbine, but a photo of the rotor of the turbine seems to hint at only three, with no space to fit the missing rows of fixed blades. A little light on the matter would be appreciated.

I did make headway in determining that last garbled heading: the part I marked ????? was “CRHD.” in the notebook, which I have taken to stand for “crosshead”. The unknown heading is then apparently the specification for the crosshead pin for each piston/crank assembly, though not being an engineer I still wonder at the difference between the crosshead pin, the piston rod screw, and the crank pin.

 

[Rancor]

 

[A. Gabriel]

Many thanks Rancor. This clears up matters considerably while I go on the hunt for more material and plans to seek out.

 

[Kareen Healey]

I would take the opportunity of this topic to ask a question about engines if someone knows the answer : in the testimony of Walter J. Howell, chairman of the BOT, Lord Mersey ask a question :
"What was the horse power of the engines of the "Titanic"? and Wilding who is, if I am right, a naval architect of Harland & Wolff, answer him with another question : "Indicated, or nominal, My Lord?" and the Commissionner answers "Nominal". ( cf: British inquiry, just above question 22573 )

My question is : what did they mean with "nominal" and "indicated" ?
Many thanks in advance!

 

[A. Gabriel]

My guess would be that "nominal" would refer to the theoretical / designed horsepower of the engines. "Indicated" would be that calculated from actual performance data.

Disclaimer, am chemist-to-be, not expert in steam engines, it would be useful if someone whose field of expertise is this would verify.

 

[B-rad]

That is about correct Gabriel. Indicated HP could be just that, the HP as indicated on a device or gauge, this does not necessarily mean the total HP capable, but the normal HP as indicated (things were not always pushed to their max) for the use of the engine, though sometimes they (indicated and max) were of the same. Indicated HP is also the HP measured by the components in which the HP was obtained such as the distance of piston travel when moving from one end of the cylinder to the other, measured with time- or something like that (I get lost in the math...). It to might not be the max HP, but is generally closer.
Nominal HP is a estimate of the relative value of the HP, most often presented lower than the indicated. For example a engine with a nominal HP of 500 may actually have an indicated HP of 620. Nominal numbers don't mean much if there is in ratio or margin given, its just a safe number so that the engines aren't pushed pass their threshold, or just to give an idea that under the best of conditions the engines should produce such values (it could even produce less value). It was based on rough calcuations and not the more scientific 'indicated' calculations.
By Titanic's time, with development in testing, and more accurate data collection and tools to obtain the data, the nominal Indicated and max should not have been too far off from one another.

 

[A. Gabriel]

Minor edit to my first post, the area for the wing propellers should be 160 sq.ft, not 120.

Also, do schematics / dimensions for Titanic's valve linkages (Stephenson linkages and Brown's engines) exist?

 

[Mike Spooner]

Cheers, Mr. Spooner. Lamentably being in the Philippines renders me fairly impeded in the ways of procuring said book til I find myself employment — though from the preview pages I have found online, there is even information there concerning the Parsons turbine of the Britannic, an excellent find indeed.

Edit: something perplexing, that book says that there were 6 stages of expansion in the Parsons turbine, but a photo of the rotor of the turbine seems to hint at only three, with no space to fit the missing rows of fixed blades. A little light on the matter would be appreciated.

I did make headway in determining that last garbled heading: the part I marked ????? was “CRHD.” in the notebook, which I have taken to stand for “crosshead”. The unknown heading is then apparently the specification for the crosshead pin for each piston/crank assembly, though not being an engineer I still wonder at the difference between the crosshead pin, the piston rod screw, and the crank pin.

The Parsons turbine sketch drawing of only 3-4 rows of blades is to give you a better view on the workings. As there are 42 rows of rotation blades which slide between the 42 rows of fix blades. The gap between the rows is very close to prevent the steam escaping to the outer diameter of the blades. The assembly is a very tricky job and requires precision alignment to prevent the blades becoming damaged. Turbines is the only form of steam power still been used today. Power stations. Jet engines work on the same priceable expect in reverse order were the air is draw in from the front.

 

[A. Gabriel]

The photo of the turbine rotor seen on the Prime Mover article was what got me wondering, because there were only three sizes of blade and I couldn’t see any separation between one expansion stage and the next. The OWM mentions 6 expansion stages, 4 of which used the 25.5” rotor blades, but in that photo above the rows of longest blades don’t seem to have breaks in the spacing to suggest new expansion stages. Hence my confusion over whether there were only 3 stages instead of 6.

Now I have managed, with some difficulty, to locate online copies of actual photos of the turbine casing here, but cannot see the fixed blades present on them. Were they installed later or is the space between fixed blades on the casing too small to resolve?

 

[Tim Aldrich]

I would say that the fixed blades had been installed later. Lining up the top half of casing (blades installed) to the bottom half would be way easier because the gaps could be watched until the casings were all but touching. Just the thought of having to do it the other way 'round would give me nightmares.

 

[Steven Christian]

I read some articles here and other places on the turbine and piston engines. What I found most impressive was the amount of time the the turbine and engines ran on the Olympic between overhauls. Mark Chirnside's article said like 20 something years for the piston engines and 7-8 for the turbine. The turbines I worked on were overhauled every 1-2 years sometimes sooner if we threw a blade or wiped a bearing. Of course they were totally different animals but still impressive they got that amount of time on Olympics drivers.

 

[Mike Spooner]

I can assure you if a turbine is correctly assemble which can be a very delicate operation and properly maintained will out last any piston engines by years. One ship that come to mind is the TS King Edward the first commercial turbine ship in the world using Charles Parsons turbines from 1901-1952. The ship has been scrapped but the turbines are in a museum now.
At Kempton Steam Museum were the worlds largest working steam engine triple expansion is housed was in operation for 50 years of service seven days twenty four hour at a steady 20rpm with no major overhaul. As next to the engine is a turbine in service for forty five years of service running at 5,750rpm without any major overhaul!
If your turbines only last for 1-2 years before trouble, there is something serious wrong!

 

[A. Gabriel]

5750 rpm!! My goodness that puts the Olympic class' turbines (195 rpm max) to shame far and wide, jeez. Even the main dynamos (325 rpm regular) never ran that fast!