Anyone have any insight into the high cylinder power achieved with a small grate with Chapelon’s 242 A1 locomotive?
The French National Railroad (Societe Nationale de Chemin de Fer) counted axles instead of wheels, so a class 242 was a 4-8-4 Northern type. Brian Hollingsworth in “Steam Passenger Locomotives” describes it as achieving “5500 hp in the cylinders”, which I guess means “indicated horsepower”, a higher amount than “wheel rim horsepower” after deduction for mechanical friction and “drawbar horsepower”, which I always thought it a nebulous measure. Especially with a high speed passenger locomotive, a lot of the power of the locomotive is overcoming air resistance where the locomotive at the lead end has much higher air resistance than the trailing cars in its draft.
Anyway, this locomotive with 2720 sq ft “heating surface”, 1249 sq ft in superheater tubes, and a 54 sq ft grate equals roughly the hp (quoted at 6000 hp “in the cylinders”) with 5271 sq ft heating surface, 2177 sq ft superheater, and 107.5 sq ft grate of a Norfolk and Western J class?
I first thought the 242A1 was designed to achieve roughly double the thermal efficiency of an American Northern to pull this off. But I also read that “the French compound (expansion steam locomotives)” were “maybe 10% more efficient than the best simples.” Wardale in “The Red Devil” suggests that Chapelon may have been “playing tricks” to get this much power from such a small locomotive, intimating the use of “the best Welsh steam coal with just the right caking tendency” so the firebed would not be blown off the grate at the combustion rates involved?
Juniatha would probably know, but I got a message from her earlier today she’s been “bounced” from the Forum, I don’t know why, my investigation hasn’t started yet. So there’s one fantastic source of knowledge concerning European steam lost to us.
More anon. You don’t want to know what Lady Firestorm has to say about this. It would have made General Patton blush! God rest his mighty soul!
I don’t know of anyone being banned by our fine hosts here at Trains.com. A Moderator may lock a thread that has reached a dead end or a stalemate of bickering t’is, t’ain’t. A Moderator may send a diplomatically worded e-mail to “cool one’s jets.” Or a Moderator may simply delete posts that unnecessarily get folks all fired up.
I have seen Juniatha “suggest parameters” on a thread, and I just read a post offering “push back” to such boundaries, and it was also unfortunate that this push back offered advice to a “non-native speaker of English.” I tried to smooth things over, in the way we do in 'Sconsin, by changing the conversation topic to “How bout dem Packers?”
Here’s to hoping that folks’ feelings all settle down and life goes on as before.
Back when Bergie was forum king he exiled several people to Siberia. Do the names Al Mayo and Mark Newton strike a chord? Not the only ones, just the ones I know about.
Second , they told me they have re-organized moderating in-house and clearly I’m ‘out-of-house’ by a decent distance I shall not moderate now – be that to the relief or regret of some or other .
So , in PRR symbolism : no more ‘Sally-One’ in stand-by , if diesels run late they’ll have to see how to make up all by themselves - gee .
Ok as concerns the Chapelon 242.A.1 :
Correct , 5500 ihp [metric] was maximum output calculated from both measuring drawbar hp and reading indicator diagrams . This was in fact a formidable output for the size of engine , both cylinder-wise and boiler-wise . It was this engine , too , that on one of her last test runs crushed the fastest electric traction train schedule between Paris and LeMans and that with a specially superincreased train consist and even including a stop for water Chartres
I have heard sources (Wardale?) claim that the best efficiency (indicated? wheel rim? drawbar?) in England of the Britannia class and one-of Duke of Gloucester reached 9 percent whereas “the French compounds” achieved 10 percent thermal efficiency.
So maybe the 242 A1 was not simply “one of the French compounds” but rather the best of the French compounds, and probably by some margin?
A good indication of thermodynamic cycle efficiency apart from the limits of combustion and heat transfer efficiency at the “front end” and mechanical friction from cylinders to wheel rim is that of the water rate. What was the evaporation rate of the 242 A1 at peak hp? If it was evaporating much less water than a U.S. Northern, that could explain how this hp was achieved with about half the grate area and half the heating surfaces?
Does “La Locomotive a Vapeur” have these data? I guess the next task is to acquire a copy of that book, and the next task after that is to exercise my limited skills in the French language?
No need to brush up on the French language… there is an excellant English translation of “La Locomotive a Vapeur” available. (I do believe there is a 2nd edition already). A web search will find a couple of dealers selling them (as well as e-bay).
That’s G.W.Carpenter’s translation, published by Camden Miniature Steam Services (ISBN 978-0953652303). For the ISBN-10, and a resource ‘back’ to other books on modern steam, see this page from the 5AT people. I don’t know about a ‘second edition’; are you sure you’re not confusing this with the recent re-reprint of Wardale’s Red Devil book?
As with all too many of these things (see Vernon Smith’s One Man’s Locomotives, the ‘rare-book’ vultures have run the price of this book up to where normal people can’t afford a copy. Even so, it’s well worth having – and using.
Paul :
guess , to find one example of the 1938 book will ask for good lookout to put it mildly …
Semper Vapore / Overmod / Dave :
It’s the 1952 edition that was translated ; unfortunately , because of the outlooks for steam and the Chapelon family of future steam was then just burning to ashes , only the first part of the two volume edition got published – the one that sort of summarized steam loco history with short looks at a lot of types and classes ; unlike the 1938 single volume edition , the book did not deal in detail with technical features of the 1950 Chapelon types nor with his testing and designing methods ; the 1938 book of course featured the earlier Super Power Types proposed for the P.O-Midi – to think of such formidable steam locomotives like the proposed dual purpose 2-10-4 of 69 in drive wheels and with large twelve wheel tender in NORD style on this rather smaller railway company , I should be tempted to say “They’d have had to take care the tender wouldn’t foul PLM property when turning her on the table - gee” Uhm – harump … of course I’d never utter such follies and so just forget what you have read .
Oh , and as the 160.A.1 indicated the 1938 types were to be six cylinder compound while the 1950 types were to be three cylinder compound – likely this was one result of Chapelon’s visit to US railroads and ALCO works in autumn 1938 . As by cylinder t.e. total the six cyl
I do have scanned images of a copy of the '38 edition (that are being used to prepare a colloquial translation of it into English at some very indefinite future date, for the use of the steam_tech Yahoo group) but they aren’t clear enough for comfortable reading – people joining the group are welcome to request access to them there. We also plan to redraw the figures as we translate the words in them, so there won’t be any copyright-violation questions when the work is done. As Juniatha says, this edition IS ‘that important’ – too important to be held to ransom by rare-book people.