From: gl4317@yahoo.com

In article ,
 Larry Sheldon  wrote:

> Thank you so much.  It looks like it might be competitive with what so
> would say is my favorite, the Mallet inverteds of my youth.


Here is a side view of a broad gauge Beyer-Garratt used in India:
http://sundar.brinkster.net/PClass.jpg
from this web page:
http://sundar.brinkster.net/Garratt.htm
It will help you see how these are put together, though the articulation
joints aren't obvious.

The Mallet style articulated locomotives had a long boiler, but it is
possible to get better heat throughput in a shorter, fatter boiler.  The
advantages seen on narrow gauge lines were certainly a factor, but those
same advantages worked on standard gauge lines as well.  Toward the end
of steam in the USA they were really pushing the limits on what could be
done with a locomotive where the driving wheels were directly under the
boiler.  The bigger the driving wheels the more speed you get at a given
RPM, but the smaller the boiler was able to be and thus the less power
available to move at speed.  The Garratt design didn't put anything
under the boiler or firebox.

This was certainly an advantage on narrow guage, but it was an advantage
anywhere.  Australia, Brazil, India and possibly Argentina used them on
their broad gauge lines.  In the side view you can see how low they
dropped the fire box below the boiler, now that the wheels are out of
the way.

Also, there were certain limitations with the Mallet design, among them
they really were not that flexible while the Beyer - Garrett had a
rotating engine piece at each end with the boiler in the center.  This
made them a bit more like the flexibility allowed with a rotating truck
at each end of a diesel or electric locomotive.

Thus, while the USA had the largest articulated locomotives on earth, a
Beyer Garratt design holds the world's speed record for an articulated
steam locomotive.  The Mallet style locomotives could be operated at
reasonable speed on really well built track, but they were rarely really
intended for fast passenger service as a regular assignment.  Due to
their stability at higher speeds, there were Beyer-Garratt designs
intended for day to day use on fast passenger trains.  In fact, before
electrification came to Sao Paulo broad gauge commuter service they used
a high speed 4-6-2+2-6-4.  Sure, from time to time a USA Mallett style
may have worked a long intercity passenger train, but daily commuter
service would have been unthinkable with them.

Also, with the weight of the water tank and fuel (coal, oil, or wood
were all used in these) directly above the engine, the weight of that
also contributed to the tractive weight of the locomotive.

All of these features made them quite popular in many parts of the
world, but oddly enough not very many of them were used in Europe, and
none were used in North America.  Asia, Australia, Africa and South
America found them very useful, however.

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