Denver & Rio Grande Western 4-6-6-4 "Challenger" Locomotives of the USA

The Denver & Rio Grande Western Railroad bought ten 4-6-6-4s from the Baldwin Locomotive Works in 1937 to speed up its freight trains. These locomotives were designated Class L-105 and were given road numbers 3700 through 3709. They had four 23 x 32 cylinders, 70" drivers, a boiler pressure of 280 psi, a tractive effort of 105,000 lbs and weighed 641,000 pounds.

Five additional Class L-105 "Challengers" arrived from Baldwin in 1942. These were similar to the Class L-105s bought in 1938 and were assigned road numbers 3710 through 3714.

In need of more locomotives to handle war-time traffic, the D&RGW ordered six more "Challengers". The War Production Board allowed six ALCO-built 4-6-6-4s to be delivered in 1943. The D&RGW did not like them, and leased them instead of buying them. These locomotives were designated Class L-97 and had four 21 x 32 cylinders, 69" drivers, a boiler pressure of 280 psi, a tractive effort of 97,350 lbs and weighed 627,000 pounds. In 1947, diesels were replacing many of the D&RGW's steam locomotives and the six Class L-97 "Challengers" were transferred to the Clinchfield Railroad.

There are no surviving D&RGW "Challengers".


Roster by Richard Duley

ClassQty.Road NumberYear Built Builder Notes
L-105103700-37091938BaldwinNumbers 3700-3709 scrapped between 1951 and 1956
L-105 53710-37141942BaldwinNumbers 3710-3714 scrapped between 1951 and 1956
L-97 63800-38051943ALCONumbers 3800-3805 sold to the Clinchfield in 1947. Became Clinchfield Class E-1 and assigned road numbers 670-675. Clinchfield numbers 670-675 scrapped in 1953.

Class Details by Steve Llanso of Sweat House Media

Class L-105 (Locobase 339)

Data from D&GRW 1 - 1952 Locomotive Diagram supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Works numbers ran 62139-62148 in 1938.

Firebox had 200 sq ft of heating surface in three thermic syphons and arch tubes. These were built for dual-service operation over the Continental Divide.

Five more were supplied in 1942 with different tube and flue counts; see Locobase 1345.


Class L-105 (Locobase 1345)

Data from D&RGW 1 - 1952 Locomotive Diagram supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Works numbers ran 64178-64182 in November 1941.

Firebox had 200 sq ft of heating surface in three thermic syphons and arch tubes as well as 206 sq ft in the combustion chamber. This second group of five engines had smaller heating surfaces and consequently different ratios from the 10 shown in Locobase 339.

A third group of six (3800-3805) L-97s were leased from the UP during World War II. They were returned to the UP, which then sold them to the Clinchfield in 1947. See the UP Challenger entry at Locobase 341..

Specifications by Steve Llanso of Sweat House Media
ClassL-105L-105
Locobase ID339 1345
RailroadDenver & Rio Grande Western (D&RGW)Denver & Rio Grande Western (D&RGW)
CountryUSAUSA
Whyte4-6-6-44-6-6-4
Number in Class105
Road Numbers3700-37093710-3714
GaugeStdStd
Number Built105
BuilderBaldwinBaldwin
Year19381941
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase12.17'12.17'
Engine Wheelbase61.50'61.50'
Ratio of driving wheelbase to overall engine wheebase 0.20 0.20
Overall Wheelbase (engine & tender)
Axle Loading (Maximum Weight per Axle)73669 lbs74721 lbs
Weight on Drivers437939 lbs435472 lbs
Engine Weight641900 lbs641700 lbs
Tender Light Weight394000 lbs393630 lbs
Total Engine and Tender Weight1035900 lbs1035330 lbs
Tender Water Capacity20000 gals20000 gals
Tender Fuel Capacity (oil/coal)26 tons26 tons
Minimum weight of rail (calculated)122 lb/yard121 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter70"70"
Boiler Pressure255 psi255 psi
Cylinders (dia x stroke)23" x 32"23" x 32"
Tractive Effort104833 lbs104833 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.18 4.15
Heating Ability
Firebox Area806 sq. ft806 sq. ft
Grate Area136.50 sq. ft136.50 sq. ft
Evaporative Heating Surface6341 sq. ft5730 sq. ft
Superheating Surface2628 sq. ft2525 sq. ft
Combined Heating Surface8969 sq. ft8255 sq. ft
Evaporative Heating Surface/Cylinder Volume206.04186.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation3480834808
Same as above plus superheater percentage4490245598
Same as above but substitute firebox area for grate area265134269244
Power L13288931402
Power MT993.40953.85

Reference


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