Example of an articulated 2-8-8-2 Mallet class locomotive
MoPac 2-8-8-2 No. 4000 "Molly" the Mallet -
The Mightiest of them All
Born at the close of
the Steam Era, Molly was not the largest Mallet ever built, but don't
be fooled. The Mallet engine such as the Baldwin-built 2-8-8-2 MoPac #4000
was a wonderously huge example of sheer brute force... these were the
most powerful steam locomotives to be seen in the U.S. Imagine a very
long and powerful engine with two full sets of drive wheels, the front
set being articulated from the body to allow the engine to ride a curve.
Like all Mallets, Molly was articulated, meaning she had at least two
sets of drivers with one able to swing away from the boiler... making
for an enormous traction base. When taking a tight curve the boiler could
overhang the rails considerably. The Mallet locomotives also reused steam
from one set of cylinders to another.
Mallet and his Grand Design
Mallets were commonly used by the railroads for slow but steady transport
of lengthy coal drags, and many (especially the earlier versions) found
use in the logging industry. Locomotive builder Baldwin didn't manufacturer
the first Mallet, but they excelled like no other. The Baldwin-Mallets
were mainly 2-6-6-2's, 2-4-4-2's and 2-8-8-2's, though similar arrangements
used were 4-8-8-4's which arguably reached somewhat past the limit that
steam technology could handle. Even bigger arrangements were proposed
in Europe but never made a reality, such as the 0-6-6-0+0-6-6-0 Garratt-Mallet.
The name "Mallet"
comes from the designer of articulated compound locomotives - Anatole
Mallet (pronounced "Malley"). To be a true Mallet locomotive,
the engine must be articulated and be a compound, meaning the steam is
used twice in separate cylinders. A simple explanation of compounding
The high pressure
cylinders use the steam first and are the smaller of the two sets, the
steam is then passed to the larger low pressure cylinders where the steam
is used again. It was supposed to be more efficient, but the complication
was maintenance intensive, and the locomotives were actually slower than
simple expansion locomotives.
The creation of the
first Mallet was simply one solution for the never-ending quest for more
horsepower. To achieve more horsepower an engine requires more heating
surface and grate area. More heating surface means larger boilers. A larger
boiler means a longer, heavier locomotive with more boiler capacity and
the greater tractive effort exerted by a larger number of drivers. There
was one real problem in order for this idea to work on rails... the fact
the mega-engine would need to round curves. So the articulation principal
of Anatole Mallet's was very appealing to the buyers of the first Mallet,
as well as the improved thermal efficiency from Mallet's approach to compounding.
The first Mallet locomotives
(early 1900's) were designed to meet the needs in Europe. The US Mallets
which came later required a number of innovations to deal with an engine
that is typically twice the size of its European counterpart. Originally
these engines were used as pusher engines on grades as steep as 2.5%.
In addition to solving traffic congestion the Mallets were very fuel
efficient, reducing the amount of fuel used per ton mile by 46%. (for
more Mallet info see http://www.ironhorse129.com/Prototype/Mallet/Baldwin65/baldwin_record_65.htm)
MoP's Mallet "Molly"
Affectionately dubbed with the name "Molly" by her crews...
she was delivered new in 1912 to the St. Louis Iron Mountain & Southern,
a predessesor to the Missouri Pacific and pressed into service in the
Dupo and St. Louis area, where she tended transfer drags and hump duties.
This is where she spent her entire career, never to stray far from her
It is easy to imagine
that such an impressive engine as Molly may have been put to use on the
most powerful runs of the day, cresting the limestone rises of Kirkwood
with a mile-long line of coal freight, but she didn't. The fact is Molly
was a blue-collar worker, through and through. Her sheer massiveness made
her ideally suited for effortlessly shuffling the high tonnage in endless
strings of cars, breaking-up and building trains at Missouri Pacific's
yard hump in St. Louis and Dupo, as well as tending transfer drags...
a sight that must have truely been awe inspiring to witness. Nothing else
owned by the road approached her, Molly was the single one of her kind
on the system.
Other than her size,
Molly was your typical MoPac steam engine with all the standard features.
In our earliest photo, on the MPHS website (mopac.org) we see Molly as
she looked prior to the merger of the MP with the Iron Mountain. Under
her cab window in small capital letters is the name "IRON MOUNTAIN",
on her middle dome is the number "4000". Her boiler is a shiney
black with her smokebox a flatter graphite color. Notice she had smaller
domes and oil-powered headlamp arrangement.
shows that as time went by, beyond the merger into Mopac, she recieved
a number of modifications. Besides regular shopping and rebuilding dictated
by the railroad, steam crews were consumate tinkerers and constantly tweaked
and made improvements to their charges, much more so than their diesel
counterparts. All steam engines became unique and one of a kind pieces
Most noticeble of
Molly's changes are the larger forward and rear domes, additional "plumbing"
mounted along her flanks, a spark arrester/flap for her smokestack, and
a more modern electric headlamp. Her tender seems to be the original car,
which also recieved new trucks and a "doghouse" for the head
In a 1936 photo (MPHS
Eagle, Vol. 19 No. 1) she's seen painted in the conservative Missouri
Pacific colors - an all-over glossy black boiler and a brighter graphite,
almost aluminum on the smokebox and firebox. A large brushed aluminum
"4000" was applied under her cab window with "M.P."
sublettering. The sublettering was also placed on either side of her squat
The Wallin Collection
photo, also on the MPHS website (mopac.org) apparently shows the locomotive
at a later date, covered in sooty grime - both the smokebox and boiler
weathered to the same shade.
MO&G 303 - Missouri Oklahoma & Gulf is a Baldwin 2-6-6-2
Mallet in Muskogee, probably on its delivery. The contributor's
granddad is at front of engine in white shirt and overalls. On the
back of the engine picture:
"Doc Epperson in white shirt taken in Muskogee Oklahoma 1911
or 13 QO&KC railroad."
Markings on engine and tender indicate it was #303 of MO&G. -
Brice Bratcher Photo/Collection
on MO&G / KO&G 2-6-6-2 Mallets
On a related note, Texas Pacific/Missouri Pacific subsidiary road Kansas,
Oklahoma & Gulf Railway inherited five Baldwin-built 2-6-6-2s, #300-304.
These five originally had been built for KO&G predecessor Missouri
Oklahoma & Gulf in 1912.
KO&G replaced these 300-series units with Sante Fe's after 15 years
Tank or tender type:
Builder / date: Baldwin
Driver diameter: 55"
Boiler pressure: 200
26x32 LP / 40x32 HP
Service History: 1912
to St. Louis Iron Mountain & Southern as #4000 ...to Missouri Pacific
RR. as #4000. Assigned to St. Louis and Dupo hump duties entire career.
MPRR service: Sold to...? Scrapped... ?
Life-Like’s Proto 2000 Heritage 2-8-8-2 Heavy Mallet in HO Scale
Rivarossi Steam 2-8-8-2 Mallet in HO Scale
Also occasionally seen in Brass
Pictures: MPHS website