History: The 4-6-6-4
class, original Challenger was designed by Otto Jabelmann of the Union
Pacific and first built by Alco for UP. Approximately 230 Challengers
were built nearly alike, differing only in their steam pressure, cylinders,
and boilers. All Challengers had either 69" or 70" drivers and
were rated at 94,400 pounds tractive effort on the Delaware Hudson to
106,900 pounds tractive effort on the Northern Pacific.
The 4-6-6-4 was often used for passenger service, but its main function
was carrying heavy, fast freight. It could average speeds of up to 70
miles per hour.
The original Challengers had 21" x 32" cylinders, 69" drivers,
255 pounds steam pressure and weighed 566,000 pounds.
The original Union Pacific Challengers were numbered from 3900 to 3939
when they came from Alco, but were renumbered to 3800 to 3839 in 1944
in order to allow space for use on later engines.
Alco modified the Challenger starting in 1942 and ending in 1944, making
a total of 105 new Challenger locomotives. These improved locomotives
had attached front engines. Springs and equalizers took up all irregularities
in the track to keep the train in equilibrium. This better balance allowed
the new Challengers to reach speeds of up to 70 miles per hour or more.
Boiler pressure was increased to 280 pounds, allowing for smaller cylinders.
Drivers were still 69", but the total wheelbase was made 5 1/4"
longer. The engine now weighed 627,000 pounds and the tractive effort
increased to 97,350 pounds.
The engines were numbered in three groups, 3950 to 3969, 3975 to 3999,
and 3930 to 3949, with the overlap mentioned earlier above.
Twin stacks were used, large sandboxes were added, as well as 14-wheel
bed type tenders of the centipede pattern. Elesco exhaust steam injectors
were mounted on the left side of some engines, and were hidden on the
inside of others. The pilot was now made of cast steel, and the boilers
were made of Bethloc deoxidized steel boilers, replacing the original
boilers, which were made of manganese.
Some engines that had been originally intended for the Union Pacific were
diverted to the Denver and Rio Grande Western. These were numbers 3800
to 3805. They did not correspond with other Challengers made by Baldwin
and were sold to Clinchfield. Clinchfield then had two types of Alco Challengers
corresponding to the two types on the Union Pacific.
Complete Kit and Accessories: The locomotive
and tender complete kit has all of the parts to build a working model. You may
wish to add your own details or purchase our "Super Detail Kit" if available.
Some models have an optional painted engineer and fireman, smoke unit kit and
other assemblies available as optional equipment to compliment your kit-building
Kit Components and Replacement Parts:
The following parts are listed in order to identify parts in your kit or to
replace parts that have been lost, damaged or simply worn out. This is
not a complete list of all of the individual parts available for this model
- please call Bowser with your specific requirements
if you cannot find the parts you need. You may also use our on-line
catalog to find parts by description. Please note that part numbers
with a price of "Call Us" may be part of an assembly and may not be available
as a separate purchase item.