Well, it's a ship, not a train. But it's one of the best explanations of how steam powered things that moved that I've ever seen.
http://www.youtube.com/watch?v=cdGo-54bknM
Railroads never really used triple expansion. They didn't have the space a ship did.
greyhounds Railroads never really used triple expansion.
Railroads never really used triple expansion.
One exception was the D&H 1403, but that reminds me of the phrase "the exception that proves the rule".
- Erik
erikem greyhounds Railroads never really used triple expansion. One exception was the D&H 1403, but that reminds me of the phrase "the exception that proves the rule". - Erik
And then there was the SNCF 160A, which wasn't exactly triple-expansion, and may or may not have proven the rule, but was certainly more workable... at least in the special French operating environment.
Listening to the commentary on the video - exhaust after the 3rd expansion was 15 psi - barely above atmospheric pressure.
Also noticed that steam was used in a closed loop condenser system to conserve water.
Never too old to have a happy childhood!
A ride on a Mississippi paddle wheel riverboat last month revealed it as a double expansion vehicle. The one thing that was a surprise was that on each of two shafts were both a HP & a LP expansion cylinder on each shaft. A measurement of that whole system appeared to be about 22 ft long for each shaft.. Not practical on a steam loco..
Tandem compounds were not that unusual in marine usage. There is a preserved Armco Steel steam towboat at Keokuk, Iowa and it is also a tandem compound.
CSSHEGEWISCH Tandem compounds were not that unusual in marine usage. There is a preserved Armco Steel steam towboat at Keokuk, Iowa and it is also a tandem compound.
Plenty of tandem compounds in railroad history -- ATSF in particular played with them. Fryer describes the ones tried in Britain. In some respects a Vauclain compound (the original form, not the subsequent balanced type) could be thought of as a tandem compound with the cylinders in parallel rather than in series.
The big issue was all that mass reciprocating in phase. After that you get to less severe issues like maintaining the piston-rod seals between the HP and LP cylinders.
Now, for fun, look at the steam motor in the Heilmann locomotive -- a steeple-compound is really a tandem or 'tridem' compound stood on end...
Are you sure that the final cylinder exhaust pressure was that high? Running a two-stage steam turbine, we routinely pulled 25 inches of vacuum at the condenser inlet.
If anyone had ever built it, the Withuhn steam engine would have been triple expansion. Same cylinder arrangement as the Leonor F. Loree, but not all driving on the same crank pin. The two pistons on the same side would have been moving in opposite directions, effectively eliminating most dynamic augment. The big problem would have been the necessity for between-the-frames linkage between the two main axles.
For a real steeple compound, how about that preserved Cornish pump engine in Upper Michigan. You could set up housekeeping in the low-pressure cylinder.
Chuck
Nope. The exception "disproves" the rule.
The old expression "The exception proves the rule" was coined at a time when folks understood the word "prove" to be a synonym for "test". If the exception is not "proof" against the rule, then the rule is not valid.
It's one of the most misused expressions I know.
So let's say railroads never used triple expansion very much.
ACYIt's one of the most misused expressions I know.
Yes, and you demonstrate yet another of the misuses. ;-}
"Exceptio probat regulam in casibus non exceptis". It's derived from legal principle, not Popperian falsifiability. "The exception proves the rule in [the] cases that are not excepted."* (Which, among other things, is just about the opposite of the 'meaning' you provide...)
(*I think that in this particular sentence, "for" is a more appropriate semantic translation than "in" to capture the sense of the original... )
Sorry for the deviation; now let's get back to the topic at hand...
Somebody show me a reference, any reference, to a Withuhn conjugated duplex being run in reciprocating triple expansion. The patent, and all the discussion regarding it, indicates no more than double expansion in the cylinders. (I quote: "the steam engines of the locomotive are in the form of a four cylinder, balanced system for driving the running gear of the locomotive. The steam expansion cycle is compounded; two high pressure cylinders exhaust into two low pressure cylinders, with all cylinders sized for equal thrust.")
To get triple expansion in the engine, you would have to design one end as a modified von Borries compound, with the one HP and one IP cylinder 'side-by-side', and the appropriate changes to the Weiss-porting bleeds to the various auxiliaries. In my opinion, the necessary arrangements for starting such a locomotive would outweigh any particular benefit from the triple expansion, even before any question of sizing the turbines driving the 'main power shaft to work with triple-expansion LP steam flow arises...
Technically, the main power shaft turbines represent an additional expansion of the steam and hence might be considered 'triple expansion'. But the arrangement has nothing whatsoever to do with what was used on D&H 1403.
Getting somewhat back to the original topic...
There's an outfit called Terrajoule that is proposing to use a combination of multiple expansion compound steam engines (engines. not turbines) with a steam accumulator to store and convert solar energy into electricity. The steam accumulator uses the same operating principle as the "fireless cooker" locomotives. The compound engines use an interesting twist, as the pressure in the accumulator drops, the higher pressure cylinders are bypassed, thus preserving optimal expansion in the low pressure cylinders.
Interesting technology, with a fair amount of thought in making something for real-world applications.
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