Photo of the Day - Santa Fe 2-6-6-2

[KCSfan]

That sure is an odd looking locomotive. The boiler jacketing at the hinged joint appears to be an accordion like affair. Does anyone know how the boiler shell (the pressure vessel itself) was connected at the hinged point? Ditto for the boiler tubes which I assume were connected by some kind of swivel fitting.

Mark

[rcdrye]

There was an article some years ago in Trains about the "prairie Mallets".  In addition to the 2-6-6-2 freight Mallets, some of which had ordinary Mallet boilers, AT&SF also had some 4-4-6-2 passenger Mallets without the flexible boiler.

Here's from E.P Alexander's classic "American Locomotives 1900-1950" (Bonanza, New York, 1950)

"Fifty rings of high carbon steel the diameter of the boiler shell and ten inches wide were riveted together alternately at their inner and outer edges to from a metal bellows which joined the two boiler sections These were each bolted to an engine frame and only one flexible steam pipe, that connecting to the high- pressure cylinders, was required.  Trouble was experienced when cinders got into the folds of the bellows causing them to burst on curves.  Other types of flexible boiler arrangements were also experimented with on six succeeding engines, but none were entirely satisfactory."

These were Baldwin built in 1911 with 69" drivers, 220 lbs boiler pressure, and 62,400lbs of tractive effort.  I seem to remember the artice said something about the tubes, but I haven't been able to locate it.

[rcdrye]

Folks who have a much better research department than I do suggest that the front part of the boiler was really more of a large superheater, and that the tubes did not go through the articulated joint.

www.steamlocomotive.com/2-6-6-2/?page=atsf

The Trains magazine articles were in the Feb 1987 issue.

[BigJim]

KCSfan

That sure is an odd looking locomotive. The boiler jacketing at the hinged joint appears to be an accordion like affair. Does anyone know how the boiler shell (the pressure vessel itself) was connected at the hinged point? Ditto for the boiler tubes which I assume were connected by some kind of swivel fitting.

Mark

Mark,
Check out the following web site for your answers.

http://www.catskillarchive.com/rrextra/blwmal00.Html

[M636C]

KCSfan

That sure is an odd looking locomotive. The boiler jacketing at the hinged joint appears to be an accordion like affair. Does anyone know how the boiler shell (the pressure vessel itself) was connected at the hinged point? Ditto for the boiler tubes which I assume were connected by some kind of swivel fitting.

Mark

The joint was not under pressure.

The two "boilers" were self contained, only the combustion gases passed across the joint at the articulation. The leading boiler was regarded as a large feed water heater. There were a number of designs of joint, the "accordion" being only one option.

The use of separate boilers allowed the leading engine unit to carry the forward boiler, giving a consistent loading to the leading low pressure engine. One of the problems of rigid boiler Mallet articulated locomotives was that the lead engine could become unloaded allowing it to slip and contributing to unsteady running.

However, the jointed boiler proved to be more trouble than it was worth and rigid boilers were used on later articulated locomotives.

M636C

[KCSfan]

Many thanks to all of you for the excellent information and links. You've cleared up the misconceptions I previously had about the boiler construction at the joint.

Mark