Intentions

You may also discover that well before the end of his employment time (I don't use the term "retirement" intentionally) he obtained an efficiency equal to one of his first compounds with the new single expansion locomotives he built.  He planned a totally revolutionary family of highly standardized 7,000 H.P. triple expansion machines featuring an increase in efficiency equivalent to the first he had achieved. And the "high speed services" type was designed for a top speed of 155mph (250km/h)...

In the initial intentions, I considered to reserve some space for data about (almost) one other major french (exactly he had both French and Swiss nationalities) locomotives designer, and his name is may be more widely known all over the world, I'm speaking of Anatole MALLET, father of the articulated steam locomotive even if it is true to say that a single expansion articulated locomotive such as those well known BIG BOY dinosaurs whose horsepower  to weight ratio is so ridiculous for those having a little knowledge in Chapelon's engine efficiency and this will be, I'm sure of that, your conviction if you read further... Sorry, you American fellows... is not a REAL Mallet because in the excellent original design the machine HAD TO BE A COUMPOUND to reduce the steam pressure supplied to the engine truck (carrying the low pressure cylinders in Mallet's design) thus preventing expensive steam leaks (they are expensive because steam is produced by heat itself obtained by the combustion of any more or less costly fossil product) at the articulations, Mallet is also the first engineer to have created 2 cylinders coumpound locomotives WHICH WORKED (and fairly well as you may discover).

Beginning of what seems to be a necessary parenthesis:

Don't misunderstand what I'm hardly trying to write! I'm not at all saying that American are "oversize" addicts without any reason as they and their engineering are often unfairly described by close-minded people. I'm sincerely sorry that my imprecise knowledge of english or anglo-american doesn't allow me to give enough shades to my writings.

It should be to forget the size of the country, its topography, and the usual loads of trains in the U.S.A., and I surely don't do that silly thing! These arguments also applies soundly to cars , airplanes, buildings, etc. design too. To try to lit my prose, I cut and paste an extract of a mail received from an U.S. visitor about this, along with my inline answer in a ping-pong mode:

VISITOR ping:

Philosophy and nationalism for a moment. Maybe it's not entirely fair to cite UP's Big Boy as an example of an American dinosaur or general excess. Actually, it was a very successful locomotive in its operating environment. I guess we americans bring this on ourselves, with some people having a "biggest is best" attitude. Wouldn't it be better to look at the differences in operating requirements between the countries, rather than dismiss U.S. designs as overweight and unrefined? As you can probably tell, my philosophy is to find reasons for differences. If you look far enough, there are usually sound, logical reasons. Of course the type of political perversity you cite in M. Chapelon's case is always the opposite of rational thought. This sort of nonsense must be nearly universal when it comes to mixing transportation and politics.

MY pong:

--> It's true to say that europeans often see americans as "superlative" or "king size" addicts... And quite often very unfairly.

VISITOR ping:

Let me try to explain (very briefly) what I believe to be one difference between our respective countries' operating requirements back in the steam era. U.S. operating philosophy called for moving enormously heavy trains. While horsepower moves trains at speed, tractive effort gets these trains started. Usable tractive effort is directly proportional to the weight on the drivers, which, to some degree, reflects the total weight of the locomotive. Without an adequate amount of weight on the drivers, a locomotive will not exert sufficient tractive effort to start the required train. Horsepower at speed cannot be used if the train can't be started.

I believe that this is one very simplistic reason that U.S. locos were heavy compared to their horsepower output. On the other hand, French operations appeared to require less emphasis on tractive effort because the trains were somewhat lighter. However, high horsepower was required to keep the trains as close to a very restrictive speed limit as possible, and to accelerate rapidly from any slow-downs. With these operating requirements, excess weight is not desirable.

MY pong:

--> I agree and adhere totally. The only thing I wanted to point out was: Try to figure out what could have been tractive efforts of your logically large and heavy engines (and I believe they had the weight and thus the grip coefficient to afford the quantum leap) if U.S. designers had followed Chapelon methods. I understand this part of text should be rewritten to reflect this. I'll try to do it by myself quickly, but any suggestion you could make is welcome.

After sending those "pongs", an idea came to my tired mind:

I hope the following simple arithmetic demonstration will be clear:

160 A's weight to tractive effort ratio: Weight 301957 lbs / tr. eff. 83700 lbs. = 3.6 lbs per lb of tractive effort.

I let you make that computation with any U.S. engine's values - integrating of course any correction factor regarding driving wheels diameters, 4.59 ft. on 160 A 1 - and conclude by yourself. No question of nationalism, I'm just trying to do an objective examination of facts. But am I objective?? I ask myself. Anyway, I really try.